- Email: [email protected]
Aligned buoyant highs, across-trench deformation, clustered volcanoes, and deep earthquakes are not aligned with plate-tectonic theory
ELSEVIER
Geomorphology 18 (1997) 199-222
Aligned buoyant highs, across-trench deformation, clustered volcanoes, and deep earthquakes are not aligned with plate-tectonic theory N. Christian Smoot Seajloor Data Bases Division, Naval Oceanographic Office, Stennis Space Center, MS 39522-5001, USA
Received 4 August 1995; revised 3 February 1996; accepted 18 May 1996
Abstract Bathymetry shows the regional interaction of aseismic, buoyant highs in northern Pacific subduction zones. Seamounts, ridges, and fractures on the seaward side of the trench are associated with events that do not support the accepted plate-tectonics paradigm, including an altered slab dip angle (Benioff zone) and the clustered volcanoes and earthquakes
within the convergent margin. Most of the examples in this study show a reduction in the number of total earthquakes but an increase in the deeper earthquakes, an abnormal amount of across-trench deformation, and a larger amount of volcanism on the active arc than if no bouyant highs existed in the subduction zone. The connections between the seaward highs and the landward clustered highs are the transverse faults, which widen by turbidite scour as they age. Forearc canyons are the modem-day bathymetric expression of these faults. All of the parameters introduced disagree with the plate-tectonic hypothesis, making an alternate explanation for the genesis necessary. That explanation falls into the realm of the surge-tectonic hypothesis, which can explain by fluid mechanics and eastward flow each of the introduced parameters. Keywords: aseismic high; trench; subduction; volcanoes; earthquakes;
1. Introduction The idea of subduction zones is a basic tenet of the plate-tectonics paradigm, a theory whose parts were finally unified by Fred Vine and Lynn Sykes at a 1966 Geological Society of America onference. Essentially, where new seafloor is created at the divergent margins, that same seafloor drifts across the ocean basin as a plate for a maximum of about 180 million years (Ma). The seaward plate bends as it approaches the subduction zone, or trench, and descends to a point where it melts and returns to its source. As the crust melts, some of the material rises to form an active arc, a string of volcanoes that 0169-555X/97/$17.00
surge tectonics
varies somewhat in distance beyond the trench on the landward plate. The subduction process causes a certain amount of earthquake activity, and the hypocenters are used to define the dip angle of the subducting plate (Benioff, 1949). The driving force of the tectonics was determined to be either one or a combination of (1) slab push at the spreading centers, (2) slab pull at the subduction zones, or (3) mantle convection cells. Expansion of the original premises provides a framework that is more closely constrained. The arrival of aseismic, buoyant highs at the trench jam the subducting mechanism so that backarc extension causes the trench to migrate around the seamount,
Copyright 0 1997 Elsevier Science B.V. All rights reserved.
PII SO169-555X(96:100027-X
200
N.C. Smoot/
Geomorphology
thereby forming a cusp (Vogt et al., 1976). Aseismic, buoyant highs halt earthquake production, but the slab continuously descends, transitioning from a shallow to a steeper dip angle (Nur and Ben-Avraham, 1983). The production of volcanoes will cease when seamounts subduct because of the reduction in magma flow (Kellerher and McCann, 1977). This idea is expanded to include no magma flow during the Neogene Period (McCabe and Uyeda, 1983), meaning that the subduction of seamounts was occurring during that time. A fourth constraint is that the subducting plate continuously dips from the surface to the mantle at 660 km, being defined by many deep earthquakes (Green, 1994; Wysession, 1995 being the latest of these). All of these tenets are part of the plate-tectonic hypothesis and have been used to explain events at subduction zones @moot, 1983a,b,c for example). Since the formulation of the plate-tectonic theory in 1966, several of the basic tenets have not withstood the test of real data. First, seamounts at the subduction zone have a positive effect on the earthquake activity, and the size of the seamount is irrelevant @moot, 1993, 1994b). The seamounts that were subducting during the Neogene are still sub-
18 (1997) 199-222
ducting. Second, earthquake clusters, appearing directly beneath volcanic clusters on the active arc across the trench from the seamounts, are deep enough not to be considered as surface noise. Moreover, they are also the only deep earthquakes (National Geophysical Data Center [NGDC] 1990 earthquake data). The antiquity of this phenomenon cannot be addressed because the NGDC earthquake data only go back 50 years. Third, on the higher stresstransfer areas adjacent to the aseismic, buoyant highs, canyons appear on the forearc. The origin of these canyons appears to be fracture controlled (Taylor and Smoot, 1984; Klaus and Taylor, 1991; Taylor, 1992). Fourth, the canyons originate in the region of the clustered volcanoes. Fifth, the trenches are in segments, and these segments have different depths (Ranneft, 1979; Smoot, 1996). Sixth, not one of the driving forces has been substantiated as of this writing, and the arguments against the hypothesis of plate-tectonics are now more convincing than in 1966 (Meyerhoff et al., 1992). The bathymetry and earthquake data will demonstrate the six points. That data will then be used to formulate a new theory that encompasses the actual events at northwest Pacific subduction zones.
Fig. 1. Locator diagram of the figures included herein. Mariana, Japan, Kuril, and Aleutian are the names of the some of the trenches surrounding the northwest Pacific plate. The Philippine plate lies to the west of the Mariana Trench, the extreme northwest is confused, and the North American plate lies north and east of the Pacific plate. Explanations for the existence of the San Andreas Fault are unsatisfactory at this time.
N.C. Smoot/Geomorphology
Fig. 2. The convergent
18 (1997) 199-222
margin from 14 to 16’N at the Magellan Seamounts
201
and southern East Mariana Ridge (from Smoot, 1988, 1991).
202
N.C. Smoot/Geomorphology
2. Methods This paper identifies the real constraints placed on the various tectonic theories by the use of actual seafloor data. The sciences of bathymetry, tectonics, and seafloor geomorphology are integrated to provide a new interpretation of landforms at northwest Pacific Ocean subduction zones. The bathymetry is updated by use of the Sonar Array Sounding System (SASS), a 1” X 1” beam width, multibeam sonar system used by the U.S. Navy. This system uses an organized grid positioned with state-of-the-art navigation. Sonar depths have been corrected to 800 fm/sec. The bathymetry of seven different regions is presented (Fig. 1). Earthquake data (NGDC 1990 CD-ROM) for the shallow region of O-100 km show 19,182 events. For the intermediate range from 100 to 300 km depth, 2,407 events are listed, and 1,495 events occurred from 300 to 660 km. Deep Sea Drilling Project (DSDP) Legs 59 and 60 and Ocean Drilling Program (ODP) Legs 125 and 126 are used to establish the timing of the multichannel seismic surveys. These help establish the location of the basement and, in some cases, its material composition. A mobile seafloor for the northern Pacific Ocean basin is theorized to have an approach angle of N55”W (DeMets, 1992). The features shown by the bathymetry are the (1) seaward aseismic, buoyant highs, (2) the trench axis depths, (3) the interaction of the aseismic, buoyant highs with the forearc, specifically the presence of canyons or other signs of fracturing, and (4) the volcanic, or active, arcs.
3. Bathymetry of north Pacific subduction zones
3.1. Magellan Seamounts The Magellan Seamounts lie seaward of the Mariana Trench from 13” to 16”N. The Pacific plate, moving northwestward, is theoretically subducting the Philippine plate, which is theoretically moving southeast in this region. The seamounts (Fig. 2) are converging on the trench, headed by delCano on the north and continuing with Quesada, Victoria, and an unnamed seamount on the south. In the north, delCano appears
18 (1997) 199-222
to have formed on a plateau at 16”N latitude whose N-S diameter is 185 km and whose E-W dimension is indeterminant. Quesada Seamount is normal faulting into the trench. The north and south flank rift zones (FRZ) on Victoria Guyot show signs of later volcanism. A rather large seamount enters the trench at 13”30’N as the trench begins to bend westward. The trench axis north of delCano is 6400 m deep. [The US Navy Ocean Survey Program collected sonar data in fathoms, and the diagrams are compiled from that data. One can convert to a sonar bottom by multiplying by 1.83 m/fm. The conversion factor to get the same depths as a 1500 m/set collector is 1.875 m/fm.] The central portion at 15”N shows an eastern, seaward trench wall that is not cluttered with stress-caused features. This trench segment is 8200 m deep. At 14”N, a rubble-free trench is marked by terraces, perched basins, and small bathymetric highs. The trench axis is deepening to the south, and the southern section is 9500 m deep. The forearc basin (Fig. 3) contains more bathymetric character than most other forearcs (see papers by Smoot, 1983a,b,c, 1988, 1991; Taylor and Smoot, 1984; Smoot and Heffner, 1986; Smoot and Richardson, 1988). Lapulapu Ridge is the largest forearc feature in this region at 55 km wide and 115 km long, and is larger than any of the seaward seamounts. The forearc seamounts align in a Z-shaped landform, presumably a function of the collision with the delCano and Quesada Seamounts. A rather large depression west of the “Z” has been interpreted as being a canyon (Karig, 1971). The forearc has four 20-25 km diameter seamounts. The East Mariana Ridge active arc is a continuous line of volcanoes @moot, 1988) at 194 km from the trench. As will be shown in this study, where buoyant highs appear in the convergent margin, volcanism is increased, and each volcano becomes a cluster of volcanoes. In the sphere of influence of the four Magellan Seamounts the active arc has 25 volcanoes in clusters of five to tbe north of Fig. 2 at 17”N, five at Zealandia Bank, three at both Farallon de Medinilla and Anatahan Islands, and eight on the south at 15”N. Esmeralda, Ruby, Guguan, and Pagan are the only active volcanoes on this segment (Bloomer et al., 1989), with Pagan erupting almost continuously since 1981 (from many Bulletins, Smithsonian Institution Staff).
N.C. Smoot/
Geomorphology
203
18 (1997) 199-222
‘ictoria
Fig. 3. 3-D views of the Magellan the forearc.
Seamount convergent
margin showing the interaction
of the Quesada Seamount
and Victoria Guyot with
204
N.C. Smoot/Geomorphology
3.2. Dutton Ridge The Dutton Ridge (Fig. 4) is obliquely subducting because the Philippine plate is growing due east by backarc extension. The stress regime is less intensive than that of the Magellan region, so possibly less stress should exist here. In theory, Fryer Guyot at the head of the Dutton Ridge appears to be abducted across the Mariana Trench, whereas the unnamed seamount to the north and Hussong Seamount to the south are subducting @moot, 1983a; Fryer and Smoot, 1985). The bathymetry of the inner trench wall and the outer arc high is very irregular. The trench axis to the north is 6950 m deep, and the trench axis to the south is 6400 m deep. On the forearc Pacman Seamount at 19”15’N and Conical Seamount at 19”30’N (Fig. 5) on the south are horst blocks of forearc material of nonvolcanic origin (Fryer and Fryer, 1987). A north-trending 37-km ridge comes off the north point of Horseshoe and ends on the inner trench wall. Horsts and ridges are formed by compressional across-trench stresses. Another group of outer arc seamounts lies to the north. A trenchparallel low lies landward of the ridge. A fracture transects the entire forearc at a bearing of N75”E. This fracture appears to be stress controlled by the arrival of Fryer Guyot. Fractures like this are presumed to have initiated formation of the forearc canyons and horsts to the north. The morphology of the canyons results from turbidity currents fed by terrigenous and volcanigenic sediments produced at the active arc over time. This idea provided a method to estimate the maturity of the forearc, with the more complex bathymetry being associated with an older forearc. Evidence to support this observation will be provided as the discussion progresses to the north in the northwest Pacific Ocean basin. The stress-pattern surface fractures across a “normal” subduction zone are in line with the approach angle of the seaward plate, which would necessarily be on a WNW azimuth for this region. Because of oblique subduction, the resultant stresses are shown by the ENE-trending fracture on the surface at this spot. Most of the stress appears to be taken up in the forearc/outer arc by seamount formation. Deeper forces, however, are at work here. For the working
18 (1997) 199-222
hypothesis, one must use the approach angle of the seaward plate of N55”W to the active arc. The surficial stress effects, such as the ENE-trending fracture, are ignored. The volcano cluster appears at 21”N latitude. A large cluster of 9 volcanoes is active and also growing @moot, 1988; Stem et al., 1984, 1989). 3.3. Unnamed seamount The convergent margin at 22”N represents the ultimate carom shot of oblique subduction, resulting more in seamount capture by the northeasterly migrating trench (Fig. 6). This seamount may be only the tail end of a much larger subducting seamount or guyot. The seamount strikes a glancing blow to the convergent margin and provides enough stress to the inner trench wall to cause the 65 km long ridge. Because no across-trench stress, no earthquake cluster, and no volcano cluster occur in such a situation, this could be a control for the present hypothesis. 3.4. Ogasawara
Plateau / Uyeda Ridge
The Ogasawara Plateau and Uyeda Ridge (Smoot, 1983b,c, 1988; Smoot and Heffner, 1986; Smoot and Richardson, 1988 among others) separate the Izu and Bonin Trenches (Fig. 7). The Bonin Trench axis is at 6950 m, and the northern Izu Trench has an 8780 m floor. The stress regime with this combined front has caused the alteration of the original trench inner wall and forearc. The central slab of the Ogasawara Plateau is abducting onto the outer arc. The horst on the southern part of the plateau, as well as the forearc canyons (Taylor and Smoot, 1984; Klaus and Taylor, 1991), are also a result of that stress. Continuing onto the forearc, the Bonin Ridge is presently not active (Horine et al., 1990), is not underlain by deep earthquakes (NGDC 1990 tape), and has been unequivocally stated to be a horst block associated with distributed rifting during the Oligocene (Taylor, 1992). Across-trench stress transfer explains these observations. The active arc of the South Honshu Ridge lies 250 km from the trench axis. The volcano clusters are Kaitoku, with at least three edifices, Kaikata with a cluster of five, and Nishino Jima with many vents.
N.C. Smoot / Geomolphology
18 (1997) 199-222
205
206
N.C. Smoot/Geomorphology
Fig. 5. 3-D views of the Fryer Guyot and Hussong fracture is readily apparent.
Seamount
18 (1997) 199-222
to the south and their interaction
with the forearc.
The small SW-trending
N.C. Smoot/Geomorphology
Kaikata is dormant, and Nishino Jima and Kaitoku are active (Bloomer et al., 1989). 3.5. Unnamed fracture
201
18 (1997) 199-222
/ contour
interval:
\ 100 fm
I
zone
A previously unreported fracture zone ridge resides in the convergent margin at 34”N (Fig. 8). The ridge strikes 042” and is up to 1100 m in height over the surrounding seafloor. The ridge is co-parallel to the Uyeda Ridge (Fi,g. 7) and the primary Dutton Ridge lineation (Fig. 41, both of which are segments of trans-Pacific fracture zones (see Smoot, 1994a, 1995 for a description of the Chinook and Mendocino fracture zones>. The trench here maintains the original bathymetric integrity. Not enough foreign material has been moved into the region to overprint that bathymetry by the arrival of this fracture ridge (Fig. 9). Still, 0 Shima Canyon may be another of the transverse faults connecting the aseismic, buoyant highs with the active arc. A deep earthquake cluster lies under NW Honshu at 36% latitude. The trench is not segmented. 3.6, Obruchev Rise The Obruchev Rise lies at the northern extreme of the Emperor Seamounts and the Emperor Fracture Zone (Smoot, 19931, seaward of the Kuril and Aleutian Trenches. The Pacific plate is theoretically unde&rusting the Eurasian plate, with motion perpendicular to the Kuril Trench (DeMets, 1992) and a small amount of possible left-lateral trench parallel motion at the collision margin. It is also sliding past the North American plate, where theoretically no outward trench migration is occurring (Van der Hilst and Seno, 1993). The Obruchev Rise presents a 130 km front to the Kuril Trench. The primary axis of the rise nearly parallels ,he Krusenstem and Stalemate Fracture Zones (Fig. 10). Ridges of the Krusenstem Fracture Zone are subducting normal to the trench. The Kuril Trench axis is 7500 m deep, whereas the Aleutian Trench axis to the NE is 6400 m deep. The Kamchatka forearc is incised by many canyons (Fig. 11). The canyons follow fault traces that formed during the Late Miocene and Early Pliocene by block subsidence (Gnibidenko and
Fig. 6. Unnamed seamount at the juncture Bonin trenches @moot, 1993).
of the Mariana
and
Svarchevskaya, 19841, presumably caused by stresstransfer on the arrival of the Obruchev Rise at the subduction zone. The canyons were widened by subaerial erosion during a low stand of the sea and continue to widen by turbidity currents and riverine erosion. The active arc is about 160 km inland from the trench axis. The Kamchatka volcanoes are in larger
Fig. 7. The convergent zone/cusp from 25 to 28”N of the Ogasawara Plateau and the South Honshu Ridge active arc at the juncture 1983b,c, 1988; Taylor and Smoot, 1984; Smoot and Heffner, 1986).
141" I
$ Nishino Jima
of the Izu and Bonin trenches (from Smoot,
N.C. Smoot/Geomorphology
clusters than in the surrounding regions. The Kliuchevskaya group (Mockler, 1993) contains 12 volcanoes, including Kamen, Kliuchevskoi, Shevaluch, and Bezimianny (Fig. 12). In keeping with the increase in activity, Kliuchevshoi has erupted 86 times since 1697 (Smithsonian Institution Staff, 1990) and is now venting gas and steam. Shevaluch had its largest eruption ever in 1854, followed by eruptions in 1981 (Dvigalo, 1988), phreatic explosions in 1984 and 1987, with the final one in 1991 (Smithsonian Institution Staff, 1993). In October 1993 Bezimianny had its largest eruption since 1956 (Mockler, 1993).
3.7. Derickson
Seamount
Derickson Seamount is a small seamount in the Gulf of Alaska (Fig. 13) a few kilometers from the Aleutian Trench axis. The Aleutian Trench axis slopes gently from 6500 m on the east to 6800 m on the west in this reg:lon and does not appear to be segmented (Lewis et al., 1988). Derickson Seamount has a large effect on the forearc and active axe. The inner trench wall and outer arc high are marked by small canyons, a perched basin, and IJnimak Seamount. The overriding North American plate is in collision with the Pacific plate according to the World stress map (Zoback and Burke, 19931, and the stress transfer has apparently created IJnimak Seamount. This trenchparallel feature is analogous to the Bonin Ridge. The forearc is incised by at least two canyons which circumscribe Unimak Seamount, forming a bathymetric moat (Fig. 14). Although no other data exist on these canyons, they are possibly transverse faults that connect the Derickson Seamount to the active al-C.
The sphere of influence of Derickson Seamount can be roughly delineated on the active arc by 16 volcanoes lying 213 km from the trench axis. The front range consists of four volcanoes on Unalaska Island, one inactive volcano on Akun Island, and ten stratovolcanoes which are roughly Plio-Pleistocene in age on Unimak Island. Bogoslaf Island (Fig. 15) lies behind the main volcanic front, but with nine eruptions since 1796 (Wood and Kienle, lQQO), Bogoslaf is included with the active arc.
18 (1997) 199-222
209
4. Morphotectonics of the north Pacific are incompatible with plate-tectonics explanations
These examples reveal the bathymetry for the entire convergent margin, or subduction zone, for seven regions along the north Pacific Ocean. The operating framework, the current plate-tectonic theory, and its fallacies were listed in the Introduction. The morphotectonics presented herein are now used to find a more meaningful paradigm to explain the constraints placed on the theory by the bathymetry, starting with trench segmentation. While working in the oil industry, Ranneft (1979) theorized that island arcs were composed of straight sections whose boundaries were at specific hinge zones. The hinges consisted of transverse faults. We now have accurate bathymetry to expand on his theory of faults and segments. Most of the aseismic, buoyant highs appear at the junctures of these trench segments, and adjacent trench segments may differ in depth by more than 4,000 m on either side of the aseismic, buoyant high. The discrete phenomena presented herein are tied together because the aseismic, buoyant highs are at one end of the transverse faults, and the clustered volcanoes are at the other. That is the first constraint in the new hypothesis. The second constraint is in the earthquake regime. Benioff (1949) discovered the relationship of the earthquake zones and the trenches. He noted the gap in seismicity at the intermediate earthquake depth, and that the descending slab was actually in two different planes, or dip angles. This relationship has been reiterated by Isacks and Barazangi (19771, Meyerhoff and Meyerhoff (19771, and this author @moot, 1993, 1994b). A study of the earthquake data (Fig. 16) for the northwest Pacific Ocean basin shows: (1) Earthquakes in the Magellan Seamount region grade from the surface to about 150 km at a 54-58” dip angle. The regime between 15”N and 18”N has a long, narrow band of 200-350 km deep earthquakes, which corresponds directly below the active volcanoes. Ninety deep earthquakes are centered between 16”N and 18”N. (2) The Benioff zone dips 28” in the upper 150 km and 74” below 250 km at the Dutton Ridge. The across-trench stress results in an earthquake swarm. The 102 deeper earthquakes in this instance are grouped below the clustered volcanoes at 21.5” to
Fig. 8. An unnamed fracture subducting
at the Izu Trench at 34”N and the forearc 0 Shima Canyon (contour interval is
X 100;
Smoot, 1994b).
34c-
35’-
N.C. Smoot / Geonwrphology
18 (1997) 199-222
N
---
Fig. 9. 3-D views of the interaction
of the unnamed fracture on the seaward side of the trench and the forearc.
211
212
k
CD
‘J
N.C. Smoot/Geomorphology
18 (1997)
199-222
N.C. Smaot/Geomorphology
18 (1997) 199-222
213
Fig. 11. (a) 3-D view from the SE perpendicular to the Kuril Trench. The west-trending lineations, especially that one bisecting the Obruchev Rise, appear to be a continuation and overprint of the Emperor Fracture Zone. The Krusenstem Fracture Zone ridges are on the west. (b) A 3-D view from the SSW looking into the Kuril Trench shows the subducting plate on the right. The heavily incised fortXUT showrs remnant outer arc highs and many canyons formed during the low stand of the sea.
22.5 i”N. (3) The epicenters associated with the subduel tion of the unnamed seamount show many shallow earthquakes and no deep ones, the deepest being
at 200 km. The plate dip angle here is 18”. (4) 1The earthquake regime at the Ogasawara Plateau/Uyc :da Ridge is primarily in the 250-400 km range frlom
214
N.C. Smoot/Geomorphology
27” to 32”N under the South Honshu Ridge, with 766 shallow earthquakes centered at 28”N and 140”45’E. The upper slab is descending at a 45” dip angle, and the lower is almost vertical. 339 deep earthquakes lie between 25”N and 29ON. (5) Where the unnamed fracture zone at 34”N latitude influences the active arc, the earthquakes again cluster at deeper than 300 km. (6) The earthquakes at the Obruchev Rise do not show a grouping of the deeper earthquake events. Instead, a gradation of 456 events descends up to 55” over the entire upper slab down to 200 km, at which point the earthquake activity apparently ceases. After
18 (1997) 199-222
a 350 km horizontal gap between the upper and lower slabs, the deep earthquakes appear again at 510 km from the trench axis and continue down to 660 km deep with a dip angle of 75-80”. The two slabs appear to be operating independently of each other and appear to represent the ultimate in decoupling. (7) The 563 earthquakes in the Derickson Seamount region are above 200 km, so no deep earthquake cluster exists. The plate does not change its dip angle every few kilometers to accommodate an obstruction to subduction unless we are dealing with a wavy descending
Fig. 12. The Kliuchevskoi volcano group on the Kamchatka peninsula (taken by astronauts aboard the Space Shuttle Endeavor in October 1994; provided by NASA, Johnson Space Center). The names have been placed using a concensus of coordinates from the Global Volcanism Network Bulletins.
N.C. Smoot/Geomorphology
plate. Because this is not manifested in the surface bathymetry of the seafloor, the existence of this subsurface phenomenon is questionable. The second
‘61 s91
18 (1997) 199-222
215
item is that the gap in seismicity in the intermediate depth range is again demonstrated. Benioff believed that the two dip angles recorded by the earthquake data reflected two mutually exclusive phenomena. The third constraint is the age of the seafloor. One last geophysical parameter is introduced, the available multichannel seismic data for the northern Pacific. The standard oceanic layers are 1, 2, and 3, where Choi (1990) has combined the available drill (DSDP and ODP data), core, and dredge hauls to produce the following. Layer 1 is Jurassic-toQuaternary sedimentary deposits; Layer 2 is Upper Proterozoic-to-Cambrian-Ordovician sedimentary deposits alternating with basalts; Layer 3 is Archaen to Lower Proterozoic gabbros. These seismic traces underlie the Japan, Kuril, and the Aleutian trenches. All of Choi’s profiles cross the entire convergent margin. All of them show that subduction cannot be occurring in the North Pacific Basin below the asthenosphere layer at 150 km. In another study Choi et al. (1992) found the regional basement to be in tension rather than compression, and the surface to be covered by compressional overprint. Other seismic reflection profiles across Kashima Seamount indicate that the landward slope has been only recently tilted toward the Japan Trench (Oshima et al., 1987). The seaward, westward-trending faults continue across the trench onto the landward side. Okamura et al. (1992) surveyed seismic profiles across the “abducted slab” of the Ogasawara Plateau that showed compressional deformation with sediments that have been slightly tilted instead of folded. This leads one to believe that the slab formed in situ and depressed when the trench formed. A fourth constraint is that of the creation/destruction process. New crust is theoretically produced at the spreading centers and consumed at the convergent margins. 80,000 km of midocean ridges (Steiner, 1977; Kennett, 1982) are producing new crust. This would add to the diameter of the planet if the same amount of new crust were not removed at the convergent margins. A problem exists with the geometry
Fig. 13. The convergent margin at Derickson Seamount from 53 to 56”N in the Gulf of Alaska. Derickson, or its predecessor by inference, has caused the Unimak Seamount on the outer arc high. (from Lewis et al., 1988; various USGS sheets).
216
N.C. Smoot/Geomorphology
in that only 30,500 km of subduction zone trenches exist. When the 9000 km of collision zones are added, the figure is still only one-half of that of the spreading centers. The introduction of such a preponderance of negative evidence causes the inquisitive mind to reflect on the validity of the plate-tectonics hypothesis. Many other geodynamics principles, such as expansion and contraction, have been reported (Steiner, 1977 for example) and, for the most part, refuted and/or ignored. A large amount of data was generated in the 1970s and 1980s following the original formulation of the plate-tectonic hypothesis in the 1960s. The data presented in the scientific literature of the 1990s is making the original paradigm less and less defendable.
Fig. 14. 3-D view from Derickson
18 (1997) 199-222
A recent (19911, widely publicized conference about alternatives to the plate-tectonic hypothesis was held at Texas Tech University (Gerhard, 1992; Love, 1993). Ideas about a pulsating Earth (Wezel, 1988; Smimoff, 1992) with surge tectonics (Meyerhoff et al., 1992) were presented. I have adapted these concepts to fit the data. The different hypotheses agree with subduction, albeit with different names and slightly different twists. The time has come to investigate these alternate hypotheses. Meyerhoff et al. (1992) synthesized decades of work in various fields and applied them to the geodynamics of Earth in the form of the surgetectonic hypothesis. Essentially, surge tectonics is a study of heat flow in the lithosphere. The flow takes place above the asthenosphere, in the lithosphere,
Seamount across the Aleution Trench showing the entire subduction
complex.
N.C. Smoot/Geomorphology
and below the surface. Surge channels are intermittent. Active paths of surge channels are marked by extensional features, traceable by the presence of volcanoes, geysers, and other similar geothermal features, and by earth.quakes. Extinct channels are marked by compressional features, such as belts of parallel fractures, fissures, and faults. The Benioff zones act as dams LO impede the progress of the surge channels, whi’ch mostly seems to be in an easterly direction. Whereas the plate-tectonic theory does not have a driving force, the surge-tectonic theory does. The surge is driven by the cooling/contraction of Earth. In each episode of cooling, the contraction causes the softened magma to surge through any available opening from the trunk-feeder surge channels by obeying the laws of fluid dynamics expounded upon by Stokes, Poiseuille, Pascal, Hooke, and Bernoulli. The surges channels are like lava tubes in a volcano. Where constrictions appear, the rate of flow is altered and energy is redirected outward (Fig. 17). An excess upwelling of the magma channel could cause the excess in volcanism on the surface, which is amply demonstrated in this study. The surge channels are an adjunct to the asthenosphere and lie just above it in the lithosphere. This explains all of the
Fig. 15. Bogoslaf Island, a part of the clustered volcanoes photograph, 1993).
18 (1997) 199-222
211
shallow earthquake activity. Intermediate earthquake activity is minimal because of the fluidity of the asthenosphere between 150 km and 300 km deep. Excess earthquake activity, however, appears below the 300 km mark directly beneath the clustered volcanoes and only beneath those regions. The deep earthquakes can be the result of downward pressure at the constrictions much the same as the upward pressure and volcano clusters exerted by the upwelling. The downward pressure pushes into the asthenosphere, which causes the deeper layer to fracture. At the same time, the lateral displacement of excess force at the constriction is a possible mechanism for the onset of a breakout channel. The breakout channel forms through a zone of weakness. This puts the cusp already in place as a result of the trench segmentation. This zone of weakness permits the easy passage of the breakout channel. The zone of weakness is the stress fracture introduced by the subducting aseismic, buoyant high. The subduction process itself only takes place in the upper regions; that is, above the asthenosphere. This explains why the seismic traces seem to pass under the trenches horizontally instead of dipping down to 660 km. Moreover, the trench segmentation and different axial depths are explained by this hy-
on the active Aleutian arc, behind the Unimak volcanoes
(W.C. Clark, Jr., pers.
n.0.191
n.o.ixL
3.0.LDL
n.c.rs,
3.0.911
R.O..9L
3.O.SCl
n.0.591 N.O.CS
.o .Sf
N.O.PS
”
N .o .95
3.O.bPi
3
3.O.C2l
3.O.ZPI
3.O.IPL H .o .6 L
H.0.95
N.O.ES
N .o .fS
3.
3.O.CPL
3.O.IPL
3.O.OPi
3.0.6CL
3.0.8CI
b4.0.62
N .o .8Z
N .o .LZ
H.0.92
N .o .sz
.LPIUS sg 30 IS!% ayl a.~ saTnbqma daap aql30 uogeso~ aq] pm sJalsnI3 ayenbqma aq,~ .daap m luasaldal slop [~XIJSaqL Qqox-a3 0661 3agN) uo!%aJ lunomeas 099 01 OOE.slop aZ.uq aql pue ‘daap w ~2 0100 I slop w!pamavf aql ‘daap q 66 010 ~0.13 sayenbqpa (I) aql 30 slawaz+da ayenbqma ‘91 %A uosyzuaa (s) pw ‘uo&x asg Aaqm.Iqg (p) ‘uo@al newId an2mese%o (E) ‘uo$aJ a%p!a uonna (z) ‘uo!%al junoureas m@$q
3.0.801
N .o .oz
.zz
“.O.IZ
H .*
N.O.CZ
N.C. Smoot/Geomorphology
18 (1997) 199-222
Fig. 17. Tectonic diagram of the effects produced on an active surge channel by the introduction of an aseismic, subduction process. The pressure arrows, caused by the constriction, explain all of the included phenomena.
pothesis. Each segment operates and exists independently of the others. By employing this hypothesis, all of the parameters in this study are explained.
219
buoyant
high into the
In a practical situation, the surge channel in this discussion for the northwest Pacific Ocean basin flows eastward out of Asia (Meyerhoff, 1996), north-
220
N.C. Smoot/Geomorphology
easterly behind the Philippine Trench, the Ryukyu Trench, and the Nankai Trough. These trenches have been in place since the Sinian (Meyerhoff et al., 1992) to the Archaen (Choi, 1990). The surge channel in this discussion has separated from the primary trunk surge channel to flow southeast behind the northwest Pacific trenches. It is surficially manifested as the active arc. Channels split off the primary trunk surge channel into breakout surge channels. Breakout surge channels occur where each trench segments, and these breaks coincides with the breaks in the Benioff zone. The breakout surge channels flow eastward, aided by the rotation of the planet. They give the appearance of the plate-tectonic phenomenon of abduction because they form behind and cross the trenches. Breakout channels form the fracture zones as they cool and collapse in a form of tectogenesis. In this case they are the unnamed (Fig. S), the Chinook off the Uyeda Ridge (Fig. 7) the Mendocino off the Dutton Ridge (Fig. 4) the Marshall-Gilberts off the Magellan Seamounts (Fig. 2) and the Caroline Ridge (insufficient bathymetry to delineate completely). The net result of the different tectonics hypotheses is the same; that is, the seamounts are consumed, but the emplacement mechanism is vastly different. In the plate-tectonics framework, the seamounts formed elsewhere, either on-ridge or by hotspot activity, and migrated to the spot they now occupy, possibly across an entire ocean basin. In the new hypothesis, the seamounts formed nearby or in situ as the breakout magma channel flowed eastward from the trunk channel underlying the active arcs. The movement is more vertical than horizontal as the aseismic, buoyant highs subduct because of contraction and compression. In either case, subduction, and its related across-trench stresses, are major factors in the production of the constriction delineated in Fig. 17, the onset of the forearc canyon formation, the clustered volcanoes, and the clustered deep earthquakes. Space prohibits the inclusion of all the corroborating evidence. In a larger Technical Report (Smoot, 1996) for the Navy similar information has been gathered for all of the convergent margins in the world. The phenomena of clustered volcanoes, clustered earthquakes, transverse faults, and aseismic, buoyant highs appear at (1) Osboume Guyot at the
18 (1997) 199-222
juncture of the Tonga and Kermadec Trenches, (2) Bougainville Guyot at the New Hebrides Trench, the (3) Nazca and (4) Cocos Ridges at the Peru Trench, the (5) Tehuantepec Ridge at the Middle America Trench, and (6) Kodiak Seamount at the Aleutian Trench. A large amount of stress occurs across the subduction zones in these examples because of horizontal and vertical motion. This stress has multiple across-trench effects on all geomorphology from the outer to the inner trench wall to the outer arc high, the forearc, and onto the active arc.
5. Conclusion The parameters introduced by this study cannot be explained by current plate-tectonic theory. SASS multibeam sonar bathymetry has revealed the aseismic, buoyant features and the volcano arcs. The NGDC earthquake data has outlined the Benioff zones and shown that clusters of earthquakes occur under the volcano clusters. The transverse faults and trench segmentation from Ranneft have been verified by the fracture-controlled canyons on the forearc across from most of the seamounts. Meyerhoff hypothesized surge channels and the eastward-flowing breakout channels. Choi described an underlayer (Layer 3) in excess of 2 Ga in age and an intermediate asthenosphere (Layed) in excess of 439 Ma. The NGDC earthquakes collected between 1967 and 1990 revealed a gap in seismicity in the intermediate earthquakes. These facts are irrefutable and confirm that the plate-tectonics theory does not work in the northern Pacific Ocean basin. Classic subduction, as defined, is not occurring. Contraction during the cooling phases is occurring, and engulfment of features formed more-or-less in situ is occurring. This process has been occurring for more than the 180 Ma predicted by the plate-tectonic hypothesis.
Acknowledgements Kudos to reviewers, Drs. Cliff Ollier and Colin Pain, who appreciated what this offering represents, “...using basic landform information to attack some of the sacred cows of plate tectonics!” The old days of bad data being better than no data have passed
N.C. Smoot/Geomorphology
into the obscurity into which they belong. Art Meyerhoff recognized the fallacies of the plate-tectonics hypothesis early on and went to his death trying to point out the various8 foibles. We had a lively exchange of ideas from 1992 until he died. Art saw the original of this paper, but we never discussed the constriction idea. I think the idea agrees nicely with the surge-tectonics hypothesis.
References Benioff, H., 1949. Seismic evidence for the fault origin of oceanic deeps. GSA Bull., 60: 1837-1856. Bloomer, S.H., Stem, R.J. and Smoot, N.C., 1989. Physical volcanology of the submarine Mariana and Volcano arcs. Bull. volcanol., 51: 210-224. Choi, D.R., 1990. Plate subduction in the Aleutian Trench questioned: a new interpretation of seismic profiles, Pac. Geol., 5: 23-33. Choi, D.R., Vasil’yev, B.I. and Bhat, MI., 1992. Paleoland, crustal structure, and composition under the northwestern Pacific Ocean. In: S. Charterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 179-191. DeMets, C., 1992. Oblique convergence and deformation along the Kuril and Japan Trenches. J. Geophys. Res., 97: 17,61517,625. Dvigalo, V.N., 1988. Growth of a dome in the crater of Shiveluch Volcano in 1980-1981 from photogrammetry data. Volt. Seis., 6: 307-315. Fryer, P. and Smoot, N.C., 1985. Processes of seamount subduction in the Mariana and Izu-Bonin trenches. Mar. Geol., 64: 77-90. Fryer, P. and Fryer, G.J., 1987. Origins of nonvolcanic seamounts in a forearc environment. In: B.H. Keating, P. Fryer, R. Batiza and G.W. Boehlert (Editors), Seamounts, Islands, and Atolls. Geophys. Monogr., 43 61-72. Gerhard, L.C., 1992. Review of New Concepts in Global Tectonics by Chatterjee and Hotton. GeoTimes, (December): 23. Gnibidenko, H.S., and Svarchevskaya, L.V., 1984. The submarine canyons of Kamchatka. Mar. Geol., 54: 277-307. Green, H.W., II, 1994. Solving the paradox of deep earthquakes. Sci. Am., 271(3): 63-71. Horine, R.L., Moore, G.L. and Taylor, B., 1990. 5. Structure of the outer Izu-Bonin forearc from seismic reflection profiling and gravity modeling. ln: P. Fryer et al. (Editors), Proc. ODP, Init. Rep., 125: 81-91 Isacks, B.L. and Barazangi, M., 1977. Geometry of Benioff zones: lateral segmentation and downwards bending of the subducted lithosphere. In: M. Talwani and W.C. Pittman III (Editors), Island Arcs, Deep Sea Trenches, and Back-arc Basins, AGU. M. Ewing Ser. 1, pp. 519-l 14. Karig, D.E., 1971. Structural history of the Mariana Island arc system. GSA Bull., 82: 323-344.
18 (1997) 199-222
221
Kellerher, J. and McCann, W., 1977. Bathymetric highs and the development of convergent plate boundaries. In M. Talwani and W.C. Pittman III (Editors), Island Arcs, Deep Sea Trenches and Back-Arc Basins. AGU, M. Ewing Ser. 1, pp. 115-122. Kennett, J.P., 1982. Marine Geology. Prentice-Hall, Englewood Cliffs, NJ, 813 pp. Klaus, A. and Taylor, B., 1991. Submarine canyon development in the Izu-Bonin forearc: a SeaMARC II and seismic survey of Aoga Shima Canyon. Mar. Geophys. Res., 13: 131-152. Lewis, S.D., Ladd, J.W. and Brun, T.R., 1988. Structural development of an accretionary prism by thrust and strike-slip faulting: Shumagin region. GSA Bull., 100: 767-782. Love, J.D., 1993. Review of The Incomplete Guide to the Art of Discovery, by Jack Oliver. J. Geol. Educ., 41: 519-520. McCabe, R. and Uyeda, S., 1983. Hypothetical model for the bending of the Mariana arc. Eos (Trans. AGU), 64(2): 16. Meyerhoff, A.A., 1996. Surge tectonic evolution of Southeastern Asia: a geodynamic approach. J. Southeast Asia Earth Sci., in press. Meyerhoff, H.A. and Meyerhoff, A.A., 1977. Genesis of island arcs. In: International Symposium on Geodynamics of the Southwest Pacific. Editions Technip, Paris, pp. 357-370. Meyerhoff, A.A., Taner, I., Morris, A.E.L., Martin, B.D., Agocs, W.B. and Meyerhoff, H.A., 1992. Surge tectonics: a new hypothesis of Earth dynamics. In: S. Chatterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 309-409. Mockler, S.B., 1993. Russian volcano erupts with little warning. Eos (Trans. AGU), 74: 537-539. Nur, A. and Ben-Avraham, Z., 1983. Volcanic gaps due to oblique consumption of aseismic ridges. In: T.W.C. Hilde and S. Uyeda (Editors), Convergence and Subduction. Tectonophysics, 99: 355-362. Okamura, Y., Murakami, F., Kishimoto, K. and Saito, E., 1992. Seismic profiling survey of the Ogasawara Plateau and the Michelson Ridge, western Pacific: evolution of Cretaceous guyots and deformation of a subducting oceanic plateau. Bull. Geol. Surv. Jpn., 43: 237-256. Oshima, S., Kasuga, S. and Kogama, K., 1987. Subduction of a large seamount into the landward slope of the Japan Trench. Mar. Geodyn., 11: 231-240. Ranneft, T.S.M., 1979. Segmentation of island arcs and application to petroleum geology. J. Pet. Geol., 1: 35-53. Smirnoff, L.S., 1992. The contracting-expanding Earth and the binary system of megacyclicity. In: S. Chatterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 441-449. Smithsonian Institution Staff, 1990. Bulletin of the Global Volcanism Network, 15: 6-8. Smithsonian Institution Staff, 1993. Bulletin of the Global Volcanism Network, 18: 2-3. Smoot, N.C., 1983a. Guyots of the Dutton Ridge at the Bonin/Mariana trench juncture as shown by multi-beam surveys. J. Geol., 91: 211-220. Smoot, N.C., 1983b. Ogasawara Plateau: multi-beam sonar bathymetry and possible tectonic implications. J. Geol., 92: 591-598.
222
N.C. Smoot/Geomorphology
Smoot, N.C., 1983~. Multi-beam surveys of the Michelson Ridge guyots: subduction or abduction. In: T.W.C. Hilde and S. Uyeda (Editors), Convergence and Subduction. Tectonophysics, 99: 363-380. Smoot, N.C., 1988. The growth rate of submarine volcanoes on the South Honshu and East Mariana Ridges. J. Volcanol. Geotherm. Res., 35: 1-15. Smoot, N.C., 1991. The Mariana Trench convergent margin at the Magellan Seamounts: tectonics and geomotphology. In: MTS ‘91 Proceedings, Vol. 1, pp. 85-91. Smoot, N.C., 1993. Geomorphic effects of seamounts in NW Pacific subduction zones. GSA Program with Abstracts, Vol. 25, p. A-319. Smoot, N.C., 1994a. Plate-wide Pacific trends orthogonal fracture intersections. Eos (Trans. AGU), 75: 69. Smoot, N.C., 1994b. The relation of seamounts to interplate deformation in the North Pacific. Eos (Trans. AGU), 75: 582. Smoot, N.C., 1995. The Chinook Trough: a trans.Pacific fracture zone. In: Proc. Third Thematic Conf. Remote Sens. Mar. Coastal Environ., Vol. 2, pp. 539-550. Smoot, N.C., 1996. Convergent Margins. NAVOCEANO Tech. Rep. 315, in review. Smoot, N.C. and Heffner, K.J., 1986. Bathymetry and possible tectonic interaction of the Uyeda Ridge with its environment. Tectonophysics, 124: 23-36. Smoot, N.C. and Richardson, D.B., 1988. Tectonic and geomorphic interpretation of the Ogasawara Plateau region by multibeam based sonar based 3-D methods. Mar. Geol., 79: 141147. Steiner, J., 1977. An expanding Earth on the basis of sea-floor spreading and subduction rates. Geology, 5: 3 13-3 18.
18 (1997) 199-222 Stem, R.J., Smoot, N.C. and Rubin, M., 1984. Unzipping of the volcano arc, Japan. In: R.L. Carlson and K. Kobayashi (Editors), Geodynamics of Back-arc Regions. Tectonophysics, 102: 153-174. Stem, R.J., Bloomer, S.H., Lin Ping-Nan and Smoot, N.C., 1989. Submarine arc volcanism in the southern Mariana arc as an ophiolite analog. Tectonophysics, 168: 151-170. Taylor, B., 1992. Rifting and the volcanic-tectonic evolution of the Izu-Bonin-Mariana arc. In: B. Taylor et al. (Editors), Proc. ODP, Sci. Results, 126: 627-651. Taylor, B. and Smoot, N.C., 1984. Morphology of Bonin forearc submarine canyons. Geology, 12: 724-727. Van der Hilst, R. and Seno, T., 1993. Effects of relative plate motion on the deep structure and penetration depth of slabs below the Izu-Bonin and Mariana island arcs. Earth Planet. Sci. Lett., 120: 375-407. Vogt, P.R., Lowrie, A., Bracey, D.R., and Hey, R.N., 1976. Subduction of aseismic ridges: effects on shape, seismicity, and other characteristics of consuming plate boundaries. GSA Spec. Pap. 172, p. 12. Wezel, F.-C., 1988. Earth structural patterns and rhythmic tectonism. In: F.-C. Wezel (Editor), The Origin and Evolution of Island Arcs. Tectonophysics, 146: 169-172. Wood, C.A. and Kienle, J., 1990. Volcanoes of North America. Cambridge University Press, Cambridge, pp. 40-50. Wysession, M., 1995. The inner workings of the Earth. Am. Sci., 83: 134-147. Zoback, M.L. and Burke, K., 1993. Lithospheric stress patterns. Eos (Trans. AGU), 74: 609-618.
Geomorphology 18 (1997) 199-222
Aligned buoyant highs, across-trench deformation, clustered volcanoes, and deep earthquakes are not aligned with plate-tectonic theory N. Christian Smoot Seajloor Data Bases Division, Naval Oceanographic Office, Stennis Space Center, MS 39522-5001, USA
Received 4 August 1995; revised 3 February 1996; accepted 18 May 1996
Abstract Bathymetry shows the regional interaction of aseismic, buoyant highs in northern Pacific subduction zones. Seamounts, ridges, and fractures on the seaward side of the trench are associated with events that do not support the accepted plate-tectonics paradigm, including an altered slab dip angle (Benioff zone) and the clustered volcanoes and earthquakes
within the convergent margin. Most of the examples in this study show a reduction in the number of total earthquakes but an increase in the deeper earthquakes, an abnormal amount of across-trench deformation, and a larger amount of volcanism on the active arc than if no bouyant highs existed in the subduction zone. The connections between the seaward highs and the landward clustered highs are the transverse faults, which widen by turbidite scour as they age. Forearc canyons are the modem-day bathymetric expression of these faults. All of the parameters introduced disagree with the plate-tectonic hypothesis, making an alternate explanation for the genesis necessary. That explanation falls into the realm of the surge-tectonic hypothesis, which can explain by fluid mechanics and eastward flow each of the introduced parameters. Keywords: aseismic high; trench; subduction; volcanoes; earthquakes;
1. Introduction The idea of subduction zones is a basic tenet of the plate-tectonics paradigm, a theory whose parts were finally unified by Fred Vine and Lynn Sykes at a 1966 Geological Society of America onference. Essentially, where new seafloor is created at the divergent margins, that same seafloor drifts across the ocean basin as a plate for a maximum of about 180 million years (Ma). The seaward plate bends as it approaches the subduction zone, or trench, and descends to a point where it melts and returns to its source. As the crust melts, some of the material rises to form an active arc, a string of volcanoes that 0169-555X/97/$17.00
surge tectonics
varies somewhat in distance beyond the trench on the landward plate. The subduction process causes a certain amount of earthquake activity, and the hypocenters are used to define the dip angle of the subducting plate (Benioff, 1949). The driving force of the tectonics was determined to be either one or a combination of (1) slab push at the spreading centers, (2) slab pull at the subduction zones, or (3) mantle convection cells. Expansion of the original premises provides a framework that is more closely constrained. The arrival of aseismic, buoyant highs at the trench jam the subducting mechanism so that backarc extension causes the trench to migrate around the seamount,
Copyright 0 1997 Elsevier Science B.V. All rights reserved.
PII SO169-555X(96:100027-X
200
N.C. Smoot/
Geomorphology
thereby forming a cusp (Vogt et al., 1976). Aseismic, buoyant highs halt earthquake production, but the slab continuously descends, transitioning from a shallow to a steeper dip angle (Nur and Ben-Avraham, 1983). The production of volcanoes will cease when seamounts subduct because of the reduction in magma flow (Kellerher and McCann, 1977). This idea is expanded to include no magma flow during the Neogene Period (McCabe and Uyeda, 1983), meaning that the subduction of seamounts was occurring during that time. A fourth constraint is that the subducting plate continuously dips from the surface to the mantle at 660 km, being defined by many deep earthquakes (Green, 1994; Wysession, 1995 being the latest of these). All of these tenets are part of the plate-tectonic hypothesis and have been used to explain events at subduction zones @moot, 1983a,b,c for example). Since the formulation of the plate-tectonic theory in 1966, several of the basic tenets have not withstood the test of real data. First, seamounts at the subduction zone have a positive effect on the earthquake activity, and the size of the seamount is irrelevant @moot, 1993, 1994b). The seamounts that were subducting during the Neogene are still sub-
18 (1997) 199-222
ducting. Second, earthquake clusters, appearing directly beneath volcanic clusters on the active arc across the trench from the seamounts, are deep enough not to be considered as surface noise. Moreover, they are also the only deep earthquakes (National Geophysical Data Center [NGDC] 1990 earthquake data). The antiquity of this phenomenon cannot be addressed because the NGDC earthquake data only go back 50 years. Third, on the higher stresstransfer areas adjacent to the aseismic, buoyant highs, canyons appear on the forearc. The origin of these canyons appears to be fracture controlled (Taylor and Smoot, 1984; Klaus and Taylor, 1991; Taylor, 1992). Fourth, the canyons originate in the region of the clustered volcanoes. Fifth, the trenches are in segments, and these segments have different depths (Ranneft, 1979; Smoot, 1996). Sixth, not one of the driving forces has been substantiated as of this writing, and the arguments against the hypothesis of plate-tectonics are now more convincing than in 1966 (Meyerhoff et al., 1992). The bathymetry and earthquake data will demonstrate the six points. That data will then be used to formulate a new theory that encompasses the actual events at northwest Pacific subduction zones.
Fig. 1. Locator diagram of the figures included herein. Mariana, Japan, Kuril, and Aleutian are the names of the some of the trenches surrounding the northwest Pacific plate. The Philippine plate lies to the west of the Mariana Trench, the extreme northwest is confused, and the North American plate lies north and east of the Pacific plate. Explanations for the existence of the San Andreas Fault are unsatisfactory at this time.
N.C. Smoot/Geomorphology
Fig. 2. The convergent
18 (1997) 199-222
margin from 14 to 16’N at the Magellan Seamounts
201
and southern East Mariana Ridge (from Smoot, 1988, 1991).
202
N.C. Smoot/Geomorphology
2. Methods This paper identifies the real constraints placed on the various tectonic theories by the use of actual seafloor data. The sciences of bathymetry, tectonics, and seafloor geomorphology are integrated to provide a new interpretation of landforms at northwest Pacific Ocean subduction zones. The bathymetry is updated by use of the Sonar Array Sounding System (SASS), a 1” X 1” beam width, multibeam sonar system used by the U.S. Navy. This system uses an organized grid positioned with state-of-the-art navigation. Sonar depths have been corrected to 800 fm/sec. The bathymetry of seven different regions is presented (Fig. 1). Earthquake data (NGDC 1990 CD-ROM) for the shallow region of O-100 km show 19,182 events. For the intermediate range from 100 to 300 km depth, 2,407 events are listed, and 1,495 events occurred from 300 to 660 km. Deep Sea Drilling Project (DSDP) Legs 59 and 60 and Ocean Drilling Program (ODP) Legs 125 and 126 are used to establish the timing of the multichannel seismic surveys. These help establish the location of the basement and, in some cases, its material composition. A mobile seafloor for the northern Pacific Ocean basin is theorized to have an approach angle of N55”W (DeMets, 1992). The features shown by the bathymetry are the (1) seaward aseismic, buoyant highs, (2) the trench axis depths, (3) the interaction of the aseismic, buoyant highs with the forearc, specifically the presence of canyons or other signs of fracturing, and (4) the volcanic, or active, arcs.
3. Bathymetry of north Pacific subduction zones
3.1. Magellan Seamounts The Magellan Seamounts lie seaward of the Mariana Trench from 13” to 16”N. The Pacific plate, moving northwestward, is theoretically subducting the Philippine plate, which is theoretically moving southeast in this region. The seamounts (Fig. 2) are converging on the trench, headed by delCano on the north and continuing with Quesada, Victoria, and an unnamed seamount on the south. In the north, delCano appears
18 (1997) 199-222
to have formed on a plateau at 16”N latitude whose N-S diameter is 185 km and whose E-W dimension is indeterminant. Quesada Seamount is normal faulting into the trench. The north and south flank rift zones (FRZ) on Victoria Guyot show signs of later volcanism. A rather large seamount enters the trench at 13”30’N as the trench begins to bend westward. The trench axis north of delCano is 6400 m deep. [The US Navy Ocean Survey Program collected sonar data in fathoms, and the diagrams are compiled from that data. One can convert to a sonar bottom by multiplying by 1.83 m/fm. The conversion factor to get the same depths as a 1500 m/set collector is 1.875 m/fm.] The central portion at 15”N shows an eastern, seaward trench wall that is not cluttered with stress-caused features. This trench segment is 8200 m deep. At 14”N, a rubble-free trench is marked by terraces, perched basins, and small bathymetric highs. The trench axis is deepening to the south, and the southern section is 9500 m deep. The forearc basin (Fig. 3) contains more bathymetric character than most other forearcs (see papers by Smoot, 1983a,b,c, 1988, 1991; Taylor and Smoot, 1984; Smoot and Heffner, 1986; Smoot and Richardson, 1988). Lapulapu Ridge is the largest forearc feature in this region at 55 km wide and 115 km long, and is larger than any of the seaward seamounts. The forearc seamounts align in a Z-shaped landform, presumably a function of the collision with the delCano and Quesada Seamounts. A rather large depression west of the “Z” has been interpreted as being a canyon (Karig, 1971). The forearc has four 20-25 km diameter seamounts. The East Mariana Ridge active arc is a continuous line of volcanoes @moot, 1988) at 194 km from the trench. As will be shown in this study, where buoyant highs appear in the convergent margin, volcanism is increased, and each volcano becomes a cluster of volcanoes. In the sphere of influence of the four Magellan Seamounts the active arc has 25 volcanoes in clusters of five to tbe north of Fig. 2 at 17”N, five at Zealandia Bank, three at both Farallon de Medinilla and Anatahan Islands, and eight on the south at 15”N. Esmeralda, Ruby, Guguan, and Pagan are the only active volcanoes on this segment (Bloomer et al., 1989), with Pagan erupting almost continuously since 1981 (from many Bulletins, Smithsonian Institution Staff).
N.C. Smoot/
Geomorphology
203
18 (1997) 199-222
‘ictoria
Fig. 3. 3-D views of the Magellan the forearc.
Seamount convergent
margin showing the interaction
of the Quesada Seamount
and Victoria Guyot with
204
N.C. Smoot/Geomorphology
3.2. Dutton Ridge The Dutton Ridge (Fig. 4) is obliquely subducting because the Philippine plate is growing due east by backarc extension. The stress regime is less intensive than that of the Magellan region, so possibly less stress should exist here. In theory, Fryer Guyot at the head of the Dutton Ridge appears to be abducted across the Mariana Trench, whereas the unnamed seamount to the north and Hussong Seamount to the south are subducting @moot, 1983a; Fryer and Smoot, 1985). The bathymetry of the inner trench wall and the outer arc high is very irregular. The trench axis to the north is 6950 m deep, and the trench axis to the south is 6400 m deep. On the forearc Pacman Seamount at 19”15’N and Conical Seamount at 19”30’N (Fig. 5) on the south are horst blocks of forearc material of nonvolcanic origin (Fryer and Fryer, 1987). A north-trending 37-km ridge comes off the north point of Horseshoe and ends on the inner trench wall. Horsts and ridges are formed by compressional across-trench stresses. Another group of outer arc seamounts lies to the north. A trenchparallel low lies landward of the ridge. A fracture transects the entire forearc at a bearing of N75”E. This fracture appears to be stress controlled by the arrival of Fryer Guyot. Fractures like this are presumed to have initiated formation of the forearc canyons and horsts to the north. The morphology of the canyons results from turbidity currents fed by terrigenous and volcanigenic sediments produced at the active arc over time. This idea provided a method to estimate the maturity of the forearc, with the more complex bathymetry being associated with an older forearc. Evidence to support this observation will be provided as the discussion progresses to the north in the northwest Pacific Ocean basin. The stress-pattern surface fractures across a “normal” subduction zone are in line with the approach angle of the seaward plate, which would necessarily be on a WNW azimuth for this region. Because of oblique subduction, the resultant stresses are shown by the ENE-trending fracture on the surface at this spot. Most of the stress appears to be taken up in the forearc/outer arc by seamount formation. Deeper forces, however, are at work here. For the working
18 (1997) 199-222
hypothesis, one must use the approach angle of the seaward plate of N55”W to the active arc. The surficial stress effects, such as the ENE-trending fracture, are ignored. The volcano cluster appears at 21”N latitude. A large cluster of 9 volcanoes is active and also growing @moot, 1988; Stem et al., 1984, 1989). 3.3. Unnamed seamount The convergent margin at 22”N represents the ultimate carom shot of oblique subduction, resulting more in seamount capture by the northeasterly migrating trench (Fig. 6). This seamount may be only the tail end of a much larger subducting seamount or guyot. The seamount strikes a glancing blow to the convergent margin and provides enough stress to the inner trench wall to cause the 65 km long ridge. Because no across-trench stress, no earthquake cluster, and no volcano cluster occur in such a situation, this could be a control for the present hypothesis. 3.4. Ogasawara
Plateau / Uyeda Ridge
The Ogasawara Plateau and Uyeda Ridge (Smoot, 1983b,c, 1988; Smoot and Heffner, 1986; Smoot and Richardson, 1988 among others) separate the Izu and Bonin Trenches (Fig. 7). The Bonin Trench axis is at 6950 m, and the northern Izu Trench has an 8780 m floor. The stress regime with this combined front has caused the alteration of the original trench inner wall and forearc. The central slab of the Ogasawara Plateau is abducting onto the outer arc. The horst on the southern part of the plateau, as well as the forearc canyons (Taylor and Smoot, 1984; Klaus and Taylor, 1991), are also a result of that stress. Continuing onto the forearc, the Bonin Ridge is presently not active (Horine et al., 1990), is not underlain by deep earthquakes (NGDC 1990 tape), and has been unequivocally stated to be a horst block associated with distributed rifting during the Oligocene (Taylor, 1992). Across-trench stress transfer explains these observations. The active arc of the South Honshu Ridge lies 250 km from the trench axis. The volcano clusters are Kaitoku, with at least three edifices, Kaikata with a cluster of five, and Nishino Jima with many vents.
N.C. Smoot / Geomolphology
18 (1997) 199-222
205
206
N.C. Smoot/Geomorphology
Fig. 5. 3-D views of the Fryer Guyot and Hussong fracture is readily apparent.
Seamount
18 (1997) 199-222
to the south and their interaction
with the forearc.
The small SW-trending
N.C. Smoot/Geomorphology
Kaikata is dormant, and Nishino Jima and Kaitoku are active (Bloomer et al., 1989). 3.5. Unnamed fracture
201
18 (1997) 199-222
/ contour
interval:
\ 100 fm
I
zone
A previously unreported fracture zone ridge resides in the convergent margin at 34”N (Fig. 8). The ridge strikes 042” and is up to 1100 m in height over the surrounding seafloor. The ridge is co-parallel to the Uyeda Ridge (Fi,g. 7) and the primary Dutton Ridge lineation (Fig. 41, both of which are segments of trans-Pacific fracture zones (see Smoot, 1994a, 1995 for a description of the Chinook and Mendocino fracture zones>. The trench here maintains the original bathymetric integrity. Not enough foreign material has been moved into the region to overprint that bathymetry by the arrival of this fracture ridge (Fig. 9). Still, 0 Shima Canyon may be another of the transverse faults connecting the aseismic, buoyant highs with the active arc. A deep earthquake cluster lies under NW Honshu at 36% latitude. The trench is not segmented. 3.6, Obruchev Rise The Obruchev Rise lies at the northern extreme of the Emperor Seamounts and the Emperor Fracture Zone (Smoot, 19931, seaward of the Kuril and Aleutian Trenches. The Pacific plate is theoretically unde&rusting the Eurasian plate, with motion perpendicular to the Kuril Trench (DeMets, 1992) and a small amount of possible left-lateral trench parallel motion at the collision margin. It is also sliding past the North American plate, where theoretically no outward trench migration is occurring (Van der Hilst and Seno, 1993). The Obruchev Rise presents a 130 km front to the Kuril Trench. The primary axis of the rise nearly parallels ,he Krusenstem and Stalemate Fracture Zones (Fig. 10). Ridges of the Krusenstem Fracture Zone are subducting normal to the trench. The Kuril Trench axis is 7500 m deep, whereas the Aleutian Trench axis to the NE is 6400 m deep. The Kamchatka forearc is incised by many canyons (Fig. 11). The canyons follow fault traces that formed during the Late Miocene and Early Pliocene by block subsidence (Gnibidenko and
Fig. 6. Unnamed seamount at the juncture Bonin trenches @moot, 1993).
of the Mariana
and
Svarchevskaya, 19841, presumably caused by stresstransfer on the arrival of the Obruchev Rise at the subduction zone. The canyons were widened by subaerial erosion during a low stand of the sea and continue to widen by turbidity currents and riverine erosion. The active arc is about 160 km inland from the trench axis. The Kamchatka volcanoes are in larger
Fig. 7. The convergent zone/cusp from 25 to 28”N of the Ogasawara Plateau and the South Honshu Ridge active arc at the juncture 1983b,c, 1988; Taylor and Smoot, 1984; Smoot and Heffner, 1986).
141" I
$ Nishino Jima
of the Izu and Bonin trenches (from Smoot,
N.C. Smoot/Geomorphology
clusters than in the surrounding regions. The Kliuchevskaya group (Mockler, 1993) contains 12 volcanoes, including Kamen, Kliuchevskoi, Shevaluch, and Bezimianny (Fig. 12). In keeping with the increase in activity, Kliuchevshoi has erupted 86 times since 1697 (Smithsonian Institution Staff, 1990) and is now venting gas and steam. Shevaluch had its largest eruption ever in 1854, followed by eruptions in 1981 (Dvigalo, 1988), phreatic explosions in 1984 and 1987, with the final one in 1991 (Smithsonian Institution Staff, 1993). In October 1993 Bezimianny had its largest eruption since 1956 (Mockler, 1993).
3.7. Derickson
Seamount
Derickson Seamount is a small seamount in the Gulf of Alaska (Fig. 13) a few kilometers from the Aleutian Trench axis. The Aleutian Trench axis slopes gently from 6500 m on the east to 6800 m on the west in this reg:lon and does not appear to be segmented (Lewis et al., 1988). Derickson Seamount has a large effect on the forearc and active axe. The inner trench wall and outer arc high are marked by small canyons, a perched basin, and IJnimak Seamount. The overriding North American plate is in collision with the Pacific plate according to the World stress map (Zoback and Burke, 19931, and the stress transfer has apparently created IJnimak Seamount. This trenchparallel feature is analogous to the Bonin Ridge. The forearc is incised by at least two canyons which circumscribe Unimak Seamount, forming a bathymetric moat (Fig. 14). Although no other data exist on these canyons, they are possibly transverse faults that connect the Derickson Seamount to the active al-C.
The sphere of influence of Derickson Seamount can be roughly delineated on the active arc by 16 volcanoes lying 213 km from the trench axis. The front range consists of four volcanoes on Unalaska Island, one inactive volcano on Akun Island, and ten stratovolcanoes which are roughly Plio-Pleistocene in age on Unimak Island. Bogoslaf Island (Fig. 15) lies behind the main volcanic front, but with nine eruptions since 1796 (Wood and Kienle, lQQO), Bogoslaf is included with the active arc.
18 (1997) 199-222
209
4. Morphotectonics of the north Pacific are incompatible with plate-tectonics explanations
These examples reveal the bathymetry for the entire convergent margin, or subduction zone, for seven regions along the north Pacific Ocean. The operating framework, the current plate-tectonic theory, and its fallacies were listed in the Introduction. The morphotectonics presented herein are now used to find a more meaningful paradigm to explain the constraints placed on the theory by the bathymetry, starting with trench segmentation. While working in the oil industry, Ranneft (1979) theorized that island arcs were composed of straight sections whose boundaries were at specific hinge zones. The hinges consisted of transverse faults. We now have accurate bathymetry to expand on his theory of faults and segments. Most of the aseismic, buoyant highs appear at the junctures of these trench segments, and adjacent trench segments may differ in depth by more than 4,000 m on either side of the aseismic, buoyant high. The discrete phenomena presented herein are tied together because the aseismic, buoyant highs are at one end of the transverse faults, and the clustered volcanoes are at the other. That is the first constraint in the new hypothesis. The second constraint is in the earthquake regime. Benioff (1949) discovered the relationship of the earthquake zones and the trenches. He noted the gap in seismicity at the intermediate earthquake depth, and that the descending slab was actually in two different planes, or dip angles. This relationship has been reiterated by Isacks and Barazangi (19771, Meyerhoff and Meyerhoff (19771, and this author @moot, 1993, 1994b). A study of the earthquake data (Fig. 16) for the northwest Pacific Ocean basin shows: (1) Earthquakes in the Magellan Seamount region grade from the surface to about 150 km at a 54-58” dip angle. The regime between 15”N and 18”N has a long, narrow band of 200-350 km deep earthquakes, which corresponds directly below the active volcanoes. Ninety deep earthquakes are centered between 16”N and 18”N. (2) The Benioff zone dips 28” in the upper 150 km and 74” below 250 km at the Dutton Ridge. The across-trench stress results in an earthquake swarm. The 102 deeper earthquakes in this instance are grouped below the clustered volcanoes at 21.5” to
Fig. 8. An unnamed fracture subducting
at the Izu Trench at 34”N and the forearc 0 Shima Canyon (contour interval is
X 100;
Smoot, 1994b).
34c-
35’-
N.C. Smoot / Geonwrphology
18 (1997) 199-222
N
---
Fig. 9. 3-D views of the interaction
of the unnamed fracture on the seaward side of the trench and the forearc.
211
212
k
CD
‘J
N.C. Smoot/Geomorphology
18 (1997)
199-222
N.C. Smaot/Geomorphology
18 (1997) 199-222
213
Fig. 11. (a) 3-D view from the SE perpendicular to the Kuril Trench. The west-trending lineations, especially that one bisecting the Obruchev Rise, appear to be a continuation and overprint of the Emperor Fracture Zone. The Krusenstem Fracture Zone ridges are on the west. (b) A 3-D view from the SSW looking into the Kuril Trench shows the subducting plate on the right. The heavily incised fortXUT showrs remnant outer arc highs and many canyons formed during the low stand of the sea.
22.5 i”N. (3) The epicenters associated with the subduel tion of the unnamed seamount show many shallow earthquakes and no deep ones, the deepest being
at 200 km. The plate dip angle here is 18”. (4) 1The earthquake regime at the Ogasawara Plateau/Uyc :da Ridge is primarily in the 250-400 km range frlom
214
N.C. Smoot/Geomorphology
27” to 32”N under the South Honshu Ridge, with 766 shallow earthquakes centered at 28”N and 140”45’E. The upper slab is descending at a 45” dip angle, and the lower is almost vertical. 339 deep earthquakes lie between 25”N and 29ON. (5) Where the unnamed fracture zone at 34”N latitude influences the active arc, the earthquakes again cluster at deeper than 300 km. (6) The earthquakes at the Obruchev Rise do not show a grouping of the deeper earthquake events. Instead, a gradation of 456 events descends up to 55” over the entire upper slab down to 200 km, at which point the earthquake activity apparently ceases. After
18 (1997) 199-222
a 350 km horizontal gap between the upper and lower slabs, the deep earthquakes appear again at 510 km from the trench axis and continue down to 660 km deep with a dip angle of 75-80”. The two slabs appear to be operating independently of each other and appear to represent the ultimate in decoupling. (7) The 563 earthquakes in the Derickson Seamount region are above 200 km, so no deep earthquake cluster exists. The plate does not change its dip angle every few kilometers to accommodate an obstruction to subduction unless we are dealing with a wavy descending
Fig. 12. The Kliuchevskoi volcano group on the Kamchatka peninsula (taken by astronauts aboard the Space Shuttle Endeavor in October 1994; provided by NASA, Johnson Space Center). The names have been placed using a concensus of coordinates from the Global Volcanism Network Bulletins.
N.C. Smoot/Geomorphology
plate. Because this is not manifested in the surface bathymetry of the seafloor, the existence of this subsurface phenomenon is questionable. The second
‘61 s91
18 (1997) 199-222
215
item is that the gap in seismicity in the intermediate depth range is again demonstrated. Benioff believed that the two dip angles recorded by the earthquake data reflected two mutually exclusive phenomena. The third constraint is the age of the seafloor. One last geophysical parameter is introduced, the available multichannel seismic data for the northern Pacific. The standard oceanic layers are 1, 2, and 3, where Choi (1990) has combined the available drill (DSDP and ODP data), core, and dredge hauls to produce the following. Layer 1 is Jurassic-toQuaternary sedimentary deposits; Layer 2 is Upper Proterozoic-to-Cambrian-Ordovician sedimentary deposits alternating with basalts; Layer 3 is Archaen to Lower Proterozoic gabbros. These seismic traces underlie the Japan, Kuril, and the Aleutian trenches. All of Choi’s profiles cross the entire convergent margin. All of them show that subduction cannot be occurring in the North Pacific Basin below the asthenosphere layer at 150 km. In another study Choi et al. (1992) found the regional basement to be in tension rather than compression, and the surface to be covered by compressional overprint. Other seismic reflection profiles across Kashima Seamount indicate that the landward slope has been only recently tilted toward the Japan Trench (Oshima et al., 1987). The seaward, westward-trending faults continue across the trench onto the landward side. Okamura et al. (1992) surveyed seismic profiles across the “abducted slab” of the Ogasawara Plateau that showed compressional deformation with sediments that have been slightly tilted instead of folded. This leads one to believe that the slab formed in situ and depressed when the trench formed. A fourth constraint is that of the creation/destruction process. New crust is theoretically produced at the spreading centers and consumed at the convergent margins. 80,000 km of midocean ridges (Steiner, 1977; Kennett, 1982) are producing new crust. This would add to the diameter of the planet if the same amount of new crust were not removed at the convergent margins. A problem exists with the geometry
Fig. 13. The convergent margin at Derickson Seamount from 53 to 56”N in the Gulf of Alaska. Derickson, or its predecessor by inference, has caused the Unimak Seamount on the outer arc high. (from Lewis et al., 1988; various USGS sheets).
216
N.C. Smoot/Geomorphology
in that only 30,500 km of subduction zone trenches exist. When the 9000 km of collision zones are added, the figure is still only one-half of that of the spreading centers. The introduction of such a preponderance of negative evidence causes the inquisitive mind to reflect on the validity of the plate-tectonics hypothesis. Many other geodynamics principles, such as expansion and contraction, have been reported (Steiner, 1977 for example) and, for the most part, refuted and/or ignored. A large amount of data was generated in the 1970s and 1980s following the original formulation of the plate-tectonic hypothesis in the 1960s. The data presented in the scientific literature of the 1990s is making the original paradigm less and less defendable.
Fig. 14. 3-D view from Derickson
18 (1997) 199-222
A recent (19911, widely publicized conference about alternatives to the plate-tectonic hypothesis was held at Texas Tech University (Gerhard, 1992; Love, 1993). Ideas about a pulsating Earth (Wezel, 1988; Smimoff, 1992) with surge tectonics (Meyerhoff et al., 1992) were presented. I have adapted these concepts to fit the data. The different hypotheses agree with subduction, albeit with different names and slightly different twists. The time has come to investigate these alternate hypotheses. Meyerhoff et al. (1992) synthesized decades of work in various fields and applied them to the geodynamics of Earth in the form of the surgetectonic hypothesis. Essentially, surge tectonics is a study of heat flow in the lithosphere. The flow takes place above the asthenosphere, in the lithosphere,
Seamount across the Aleution Trench showing the entire subduction
complex.
N.C. Smoot/Geomorphology
and below the surface. Surge channels are intermittent. Active paths of surge channels are marked by extensional features, traceable by the presence of volcanoes, geysers, and other similar geothermal features, and by earth.quakes. Extinct channels are marked by compressional features, such as belts of parallel fractures, fissures, and faults. The Benioff zones act as dams LO impede the progress of the surge channels, whi’ch mostly seems to be in an easterly direction. Whereas the plate-tectonic theory does not have a driving force, the surge-tectonic theory does. The surge is driven by the cooling/contraction of Earth. In each episode of cooling, the contraction causes the softened magma to surge through any available opening from the trunk-feeder surge channels by obeying the laws of fluid dynamics expounded upon by Stokes, Poiseuille, Pascal, Hooke, and Bernoulli. The surges channels are like lava tubes in a volcano. Where constrictions appear, the rate of flow is altered and energy is redirected outward (Fig. 17). An excess upwelling of the magma channel could cause the excess in volcanism on the surface, which is amply demonstrated in this study. The surge channels are an adjunct to the asthenosphere and lie just above it in the lithosphere. This explains all of the
Fig. 15. Bogoslaf Island, a part of the clustered volcanoes photograph, 1993).
18 (1997) 199-222
211
shallow earthquake activity. Intermediate earthquake activity is minimal because of the fluidity of the asthenosphere between 150 km and 300 km deep. Excess earthquake activity, however, appears below the 300 km mark directly beneath the clustered volcanoes and only beneath those regions. The deep earthquakes can be the result of downward pressure at the constrictions much the same as the upward pressure and volcano clusters exerted by the upwelling. The downward pressure pushes into the asthenosphere, which causes the deeper layer to fracture. At the same time, the lateral displacement of excess force at the constriction is a possible mechanism for the onset of a breakout channel. The breakout channel forms through a zone of weakness. This puts the cusp already in place as a result of the trench segmentation. This zone of weakness permits the easy passage of the breakout channel. The zone of weakness is the stress fracture introduced by the subducting aseismic, buoyant high. The subduction process itself only takes place in the upper regions; that is, above the asthenosphere. This explains why the seismic traces seem to pass under the trenches horizontally instead of dipping down to 660 km. Moreover, the trench segmentation and different axial depths are explained by this hy-
on the active Aleutian arc, behind the Unimak volcanoes
(W.C. Clark, Jr., pers.
n.0.191
n.o.ixL
3.0.LDL
n.c.rs,
3.0.911
R.O..9L
3.O.SCl
n.0.591 N.O.CS
.o .Sf
N.O.PS
”
N .o .95
3.O.bPi
3
3.O.C2l
3.O.ZPI
3.O.IPL H .o .6 L
H.0.95
N.O.ES
N .o .fS
3.
3.O.CPL
3.O.IPL
3.O.OPi
3.0.6CL
3.0.8CI
b4.0.62
N .o .8Z
N .o .LZ
H.0.92
N .o .sz
.LPIUS sg 30 IS!% ayl a.~ saTnbqma daap aql30 uogeso~ aq] pm sJalsnI3 ayenbqma aq,~ .daap m luasaldal slop [~XIJSaqL Qqox-a3 0661 3agN) uo!%aJ lunomeas 099 01 OOE.slop aZ.uq aql pue ‘daap w ~2 0100 I slop w!pamavf aql ‘daap q 66 010 ~0.13 sayenbqpa (I) aql 30 slawaz+da ayenbqma ‘91 %A uosyzuaa (s) pw ‘uo&x asg Aaqm.Iqg (p) ‘uo@al newId an2mese%o (E) ‘uo$aJ a%p!a uonna (z) ‘uo!%al junoureas m@$q
3.0.801
N .o .oz
.zz
“.O.IZ
H .*
N.O.CZ
N.C. Smoot/Geomorphology
18 (1997) 199-222
Fig. 17. Tectonic diagram of the effects produced on an active surge channel by the introduction of an aseismic, subduction process. The pressure arrows, caused by the constriction, explain all of the included phenomena.
pothesis. Each segment operates and exists independently of the others. By employing this hypothesis, all of the parameters in this study are explained.
219
buoyant
high into the
In a practical situation, the surge channel in this discussion for the northwest Pacific Ocean basin flows eastward out of Asia (Meyerhoff, 1996), north-
220
N.C. Smoot/Geomorphology
easterly behind the Philippine Trench, the Ryukyu Trench, and the Nankai Trough. These trenches have been in place since the Sinian (Meyerhoff et al., 1992) to the Archaen (Choi, 1990). The surge channel in this discussion has separated from the primary trunk surge channel to flow southeast behind the northwest Pacific trenches. It is surficially manifested as the active arc. Channels split off the primary trunk surge channel into breakout surge channels. Breakout surge channels occur where each trench segments, and these breaks coincides with the breaks in the Benioff zone. The breakout surge channels flow eastward, aided by the rotation of the planet. They give the appearance of the plate-tectonic phenomenon of abduction because they form behind and cross the trenches. Breakout channels form the fracture zones as they cool and collapse in a form of tectogenesis. In this case they are the unnamed (Fig. S), the Chinook off the Uyeda Ridge (Fig. 7) the Mendocino off the Dutton Ridge (Fig. 4) the Marshall-Gilberts off the Magellan Seamounts (Fig. 2) and the Caroline Ridge (insufficient bathymetry to delineate completely). The net result of the different tectonics hypotheses is the same; that is, the seamounts are consumed, but the emplacement mechanism is vastly different. In the plate-tectonics framework, the seamounts formed elsewhere, either on-ridge or by hotspot activity, and migrated to the spot they now occupy, possibly across an entire ocean basin. In the new hypothesis, the seamounts formed nearby or in situ as the breakout magma channel flowed eastward from the trunk channel underlying the active arcs. The movement is more vertical than horizontal as the aseismic, buoyant highs subduct because of contraction and compression. In either case, subduction, and its related across-trench stresses, are major factors in the production of the constriction delineated in Fig. 17, the onset of the forearc canyon formation, the clustered volcanoes, and the clustered deep earthquakes. Space prohibits the inclusion of all the corroborating evidence. In a larger Technical Report (Smoot, 1996) for the Navy similar information has been gathered for all of the convergent margins in the world. The phenomena of clustered volcanoes, clustered earthquakes, transverse faults, and aseismic, buoyant highs appear at (1) Osboume Guyot at the
18 (1997) 199-222
juncture of the Tonga and Kermadec Trenches, (2) Bougainville Guyot at the New Hebrides Trench, the (3) Nazca and (4) Cocos Ridges at the Peru Trench, the (5) Tehuantepec Ridge at the Middle America Trench, and (6) Kodiak Seamount at the Aleutian Trench. A large amount of stress occurs across the subduction zones in these examples because of horizontal and vertical motion. This stress has multiple across-trench effects on all geomorphology from the outer to the inner trench wall to the outer arc high, the forearc, and onto the active arc.
5. Conclusion The parameters introduced by this study cannot be explained by current plate-tectonic theory. SASS multibeam sonar bathymetry has revealed the aseismic, buoyant features and the volcano arcs. The NGDC earthquake data has outlined the Benioff zones and shown that clusters of earthquakes occur under the volcano clusters. The transverse faults and trench segmentation from Ranneft have been verified by the fracture-controlled canyons on the forearc across from most of the seamounts. Meyerhoff hypothesized surge channels and the eastward-flowing breakout channels. Choi described an underlayer (Layer 3) in excess of 2 Ga in age and an intermediate asthenosphere (Layed) in excess of 439 Ma. The NGDC earthquakes collected between 1967 and 1990 revealed a gap in seismicity in the intermediate earthquakes. These facts are irrefutable and confirm that the plate-tectonics theory does not work in the northern Pacific Ocean basin. Classic subduction, as defined, is not occurring. Contraction during the cooling phases is occurring, and engulfment of features formed more-or-less in situ is occurring. This process has been occurring for more than the 180 Ma predicted by the plate-tectonic hypothesis.
Acknowledgements Kudos to reviewers, Drs. Cliff Ollier and Colin Pain, who appreciated what this offering represents, “...using basic landform information to attack some of the sacred cows of plate tectonics!” The old days of bad data being better than no data have passed
N.C. Smoot/Geomorphology
into the obscurity into which they belong. Art Meyerhoff recognized the fallacies of the plate-tectonics hypothesis early on and went to his death trying to point out the various8 foibles. We had a lively exchange of ideas from 1992 until he died. Art saw the original of this paper, but we never discussed the constriction idea. I think the idea agrees nicely with the surge-tectonics hypothesis.
References Benioff, H., 1949. Seismic evidence for the fault origin of oceanic deeps. GSA Bull., 60: 1837-1856. Bloomer, S.H., Stem, R.J. and Smoot, N.C., 1989. Physical volcanology of the submarine Mariana and Volcano arcs. Bull. volcanol., 51: 210-224. Choi, D.R., 1990. Plate subduction in the Aleutian Trench questioned: a new interpretation of seismic profiles, Pac. Geol., 5: 23-33. Choi, D.R., Vasil’yev, B.I. and Bhat, MI., 1992. Paleoland, crustal structure, and composition under the northwestern Pacific Ocean. In: S. Charterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 179-191. DeMets, C., 1992. Oblique convergence and deformation along the Kuril and Japan Trenches. J. Geophys. Res., 97: 17,61517,625. Dvigalo, V.N., 1988. Growth of a dome in the crater of Shiveluch Volcano in 1980-1981 from photogrammetry data. Volt. Seis., 6: 307-315. Fryer, P. and Smoot, N.C., 1985. Processes of seamount subduction in the Mariana and Izu-Bonin trenches. Mar. Geol., 64: 77-90. Fryer, P. and Fryer, G.J., 1987. Origins of nonvolcanic seamounts in a forearc environment. In: B.H. Keating, P. Fryer, R. Batiza and G.W. Boehlert (Editors), Seamounts, Islands, and Atolls. Geophys. Monogr., 43 61-72. Gerhard, L.C., 1992. Review of New Concepts in Global Tectonics by Chatterjee and Hotton. GeoTimes, (December): 23. Gnibidenko, H.S., and Svarchevskaya, L.V., 1984. The submarine canyons of Kamchatka. Mar. Geol., 54: 277-307. Green, H.W., II, 1994. Solving the paradox of deep earthquakes. Sci. Am., 271(3): 63-71. Horine, R.L., Moore, G.L. and Taylor, B., 1990. 5. Structure of the outer Izu-Bonin forearc from seismic reflection profiling and gravity modeling. ln: P. Fryer et al. (Editors), Proc. ODP, Init. Rep., 125: 81-91 Isacks, B.L. and Barazangi, M., 1977. Geometry of Benioff zones: lateral segmentation and downwards bending of the subducted lithosphere. In: M. Talwani and W.C. Pittman III (Editors), Island Arcs, Deep Sea Trenches, and Back-arc Basins, AGU. M. Ewing Ser. 1, pp. 519-l 14. Karig, D.E., 1971. Structural history of the Mariana Island arc system. GSA Bull., 82: 323-344.
18 (1997) 199-222
221
Kellerher, J. and McCann, W., 1977. Bathymetric highs and the development of convergent plate boundaries. In M. Talwani and W.C. Pittman III (Editors), Island Arcs, Deep Sea Trenches and Back-Arc Basins. AGU, M. Ewing Ser. 1, pp. 115-122. Kennett, J.P., 1982. Marine Geology. Prentice-Hall, Englewood Cliffs, NJ, 813 pp. Klaus, A. and Taylor, B., 1991. Submarine canyon development in the Izu-Bonin forearc: a SeaMARC II and seismic survey of Aoga Shima Canyon. Mar. Geophys. Res., 13: 131-152. Lewis, S.D., Ladd, J.W. and Brun, T.R., 1988. Structural development of an accretionary prism by thrust and strike-slip faulting: Shumagin region. GSA Bull., 100: 767-782. Love, J.D., 1993. Review of The Incomplete Guide to the Art of Discovery, by Jack Oliver. J. Geol. Educ., 41: 519-520. McCabe, R. and Uyeda, S., 1983. Hypothetical model for the bending of the Mariana arc. Eos (Trans. AGU), 64(2): 16. Meyerhoff, A.A., 1996. Surge tectonic evolution of Southeastern Asia: a geodynamic approach. J. Southeast Asia Earth Sci., in press. Meyerhoff, H.A. and Meyerhoff, A.A., 1977. Genesis of island arcs. In: International Symposium on Geodynamics of the Southwest Pacific. Editions Technip, Paris, pp. 357-370. Meyerhoff, A.A., Taner, I., Morris, A.E.L., Martin, B.D., Agocs, W.B. and Meyerhoff, H.A., 1992. Surge tectonics: a new hypothesis of Earth dynamics. In: S. Chatterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 309-409. Mockler, S.B., 1993. Russian volcano erupts with little warning. Eos (Trans. AGU), 74: 537-539. Nur, A. and Ben-Avraham, Z., 1983. Volcanic gaps due to oblique consumption of aseismic ridges. In: T.W.C. Hilde and S. Uyeda (Editors), Convergence and Subduction. Tectonophysics, 99: 355-362. Okamura, Y., Murakami, F., Kishimoto, K. and Saito, E., 1992. Seismic profiling survey of the Ogasawara Plateau and the Michelson Ridge, western Pacific: evolution of Cretaceous guyots and deformation of a subducting oceanic plateau. Bull. Geol. Surv. Jpn., 43: 237-256. Oshima, S., Kasuga, S. and Kogama, K., 1987. Subduction of a large seamount into the landward slope of the Japan Trench. Mar. Geodyn., 11: 231-240. Ranneft, T.S.M., 1979. Segmentation of island arcs and application to petroleum geology. J. Pet. Geol., 1: 35-53. Smirnoff, L.S., 1992. The contracting-expanding Earth and the binary system of megacyclicity. In: S. Chatterjee and N. Hotton III (Editors), New Concepts in Global Tectonics. Texas Tech University Press, Lubbock, TX, pp. 441-449. Smithsonian Institution Staff, 1990. Bulletin of the Global Volcanism Network, 15: 6-8. Smithsonian Institution Staff, 1993. Bulletin of the Global Volcanism Network, 18: 2-3. Smoot, N.C., 1983a. Guyots of the Dutton Ridge at the Bonin/Mariana trench juncture as shown by multi-beam surveys. J. Geol., 91: 211-220. Smoot, N.C., 1983b. Ogasawara Plateau: multi-beam sonar bathymetry and possible tectonic implications. J. Geol., 92: 591-598.
222
N.C. Smoot/Geomorphology
Smoot, N.C., 1983~. Multi-beam surveys of the Michelson Ridge guyots: subduction or abduction. In: T.W.C. Hilde and S. Uyeda (Editors), Convergence and Subduction. Tectonophysics, 99: 363-380. Smoot, N.C., 1988. The growth rate of submarine volcanoes on the South Honshu and East Mariana Ridges. J. Volcanol. Geotherm. Res., 35: 1-15. Smoot, N.C., 1991. The Mariana Trench convergent margin at the Magellan Seamounts: tectonics and geomotphology. In: MTS ‘91 Proceedings, Vol. 1, pp. 85-91. Smoot, N.C., 1993. Geomorphic effects of seamounts in NW Pacific subduction zones. GSA Program with Abstracts, Vol. 25, p. A-319. Smoot, N.C., 1994a. Plate-wide Pacific trends orthogonal fracture intersections. Eos (Trans. AGU), 75: 69. Smoot, N.C., 1994b. The relation of seamounts to interplate deformation in the North Pacific. Eos (Trans. AGU), 75: 582. Smoot, N.C., 1995. The Chinook Trough: a trans.Pacific fracture zone. In: Proc. Third Thematic Conf. Remote Sens. Mar. Coastal Environ., Vol. 2, pp. 539-550. Smoot, N.C., 1996. Convergent Margins. NAVOCEANO Tech. Rep. 315, in review. Smoot, N.C. and Heffner, K.J., 1986. Bathymetry and possible tectonic interaction of the Uyeda Ridge with its environment. Tectonophysics, 124: 23-36. Smoot, N.C. and Richardson, D.B., 1988. Tectonic and geomorphic interpretation of the Ogasawara Plateau region by multibeam based sonar based 3-D methods. Mar. Geol., 79: 141147. Steiner, J., 1977. An expanding Earth on the basis of sea-floor spreading and subduction rates. Geology, 5: 3 13-3 18.
18 (1997) 199-222 Stem, R.J., Smoot, N.C. and Rubin, M., 1984. Unzipping of the volcano arc, Japan. In: R.L. Carlson and K. Kobayashi (Editors), Geodynamics of Back-arc Regions. Tectonophysics, 102: 153-174. Stem, R.J., Bloomer, S.H., Lin Ping-Nan and Smoot, N.C., 1989. Submarine arc volcanism in the southern Mariana arc as an ophiolite analog. Tectonophysics, 168: 151-170. Taylor, B., 1992. Rifting and the volcanic-tectonic evolution of the Izu-Bonin-Mariana arc. In: B. Taylor et al. (Editors), Proc. ODP, Sci. Results, 126: 627-651. Taylor, B. and Smoot, N.C., 1984. Morphology of Bonin forearc submarine canyons. Geology, 12: 724-727. Van der Hilst, R. and Seno, T., 1993. Effects of relative plate motion on the deep structure and penetration depth of slabs below the Izu-Bonin and Mariana island arcs. Earth Planet. Sci. Lett., 120: 375-407. Vogt, P.R., Lowrie, A., Bracey, D.R., and Hey, R.N., 1976. Subduction of aseismic ridges: effects on shape, seismicity, and other characteristics of consuming plate boundaries. GSA Spec. Pap. 172, p. 12. Wezel, F.-C., 1988. Earth structural patterns and rhythmic tectonism. In: F.-C. Wezel (Editor), The Origin and Evolution of Island Arcs. Tectonophysics, 146: 169-172. Wood, C.A. and Kienle, J., 1990. Volcanoes of North America. Cambridge University Press, Cambridge, pp. 40-50. Wysession, M., 1995. The inner workings of the Earth. Am. Sci., 83: 134-147. Zoback, M.L. and Burke, K., 1993. Lithospheric stress patterns. Eos (Trans. AGU), 74: 609-618.