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Satellite measurement of sulfur dioxide from the Redoubt eruptions of 1989–1990
Jo.m'nalofvoicanology. and geothermalresearch ELSEVIER
Journal of Volcanologyand Geothermal Research 62 (1994) 353-357
Satellite measurement of sulfur dioxide from the Redoubt eruptions of 1989-1990 C.C. Schnetzler a, S.D. D o i r o n b, L.S. Walter a, A.J. Krueger ~ aEarth Sciences Directorate, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA bHughes STX Corporation, Lanham, MD, USA Received 9 May 1991; accepted 20 September 1993
Abstract
The mass of SO2 emitted by the 16 major explosive eruptions of Redoubt Volcano between December 1989 and April 1990 have been examined by the Total Ozone Mapping Spectrometer (TOMS) carried on the Nimbus 7 satellite. Because of low light levels during the winter months, TOMS could not detect SO2 at high northern latitudes. Thus, the major eruptions from December through February could not be monitored unless winds brought the clouds to latitudes lower than about 58°N. Only two SO2 clouds were observed in the satellite data - - an approximately 100-kiloton (kt) cloud on December 16 over Nevada and eastern California, and a 10-kt cloud on March 9 directly over the volcano. We speculate that the major eruption on December 15 at 1015 hour produced the 100-kt cloud seen on December 16, and the mass of SO2 injected into the atmosphere at that time was 175 + 50 kt.
1. Introduction
During the four-month period, from mid-December 1989 to mid-April 1990, Redoubt Volcano, Alaska experienced a number of short explosive eruptions (Alaska Volcano Observatory Staff, 1990; Brantley, 1990; see Table 1 ). We have used data from the Total Ozone Mapping Spectrometer (TOMS) carded on the Nimbus 7 satellite to measure SO2 emitted by these explosive eruptions of Redoubt Volcano. As the name denotes, TOMS was designed to measure atmospheric ozone; however, it was discovered during the 1982 eruption of E1 Chichon that SO2 is also detectable by this sensor. TOMS records the absorption of ultraviolet light by ozone and SO2, and differential absorption in TOMS' six ultraviolet bands allows separation of these two gases
(Krueger, 1983). The instrument has a maxim u m spatial resolution (pixel size) of 50 km at nadir and an average resolution across the scan of 66 km. The noise level for an average size single pixel is about 500 metric tons (0.5 kt) SO2. However, background variation (zero offset range) is about 1 or 2 kt. We consider this the detection limit per pixel, but as a cloud is defined as several contiguous pixels above background variation, our cloud detection limit is about 5 to 10 kt. The Nimbus 7 orbit and TOMS swath width provide daily global coverage, with an approximately noon local time overpass. We have examined the satellite data taken on, and for several days subsequent to, the date of major Redoubt explosive eruptions. The dates of the explosive eruptions and the dates we searched the TOMS data for SO2 clouds are given in Table
0377-0273/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSD10377-0273 (93) E0100-G
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C C. Schnetzler et al. / Jounra/ ~?/ Volcanology and Geothermal Research 62 (1 t)94) 353-35 7
1. During the winter months TOMS could not record data directly over Redoubt Volcano (latitude 60.4 °N) due to insufficient ultraviolet light levels above about 58 ° to 60°N. Wind patterns on some of the days we examined, however, were to the south and east, either directly or after a relatively minor excursion to the north, so that any SO2 cloud should be brought southward into the area of detectability. By early March the ultraviolet light level was sufficient to obtain data as far north as 65 °.
2. Observations For the 16 reported major eruptions of Redoubt Volcano on 13 days between December 14, 1989 and April 15, 1990 (Table 1 ), we detected only two SO2 clouds. The larger of these two clouds was observed on December 16 and 17. Figure 1 shows the SO2 cloud on December 16, with an area of about 120,000 square kilometers, located over Nevada and eastern California. The quantity of SO2 can be calculated by integrating the column SO2 amounts across the cloud and correcting for background amounts (Krueger,
1983; Krueger et al., 1990 ). On this day the cloud contained 100 ( + 15 ) kt of SO2. On December 15, the winds at all altitudes over North America, as determined from National Meteorology Center data, were strong to the north over Redoubt Volcano, turning eastward at about 70 ° N, and then in a southeastern direction over western Canada and western United States (Fig. 1 ). Thus, the cloud observed on December 16 had traveled approximately 4500 km from the volcano to Nevada. Twenty-four hours later, on December 17, the cloud had traveled an additional 1100 km to off the coast of Baja California. At this time the cloud contained only about 30 kt SO2. The cloud dissipated below the detection limit by the time of overpass on December 18. On March 9, 1990 a small, four-pixel SO2 cloud was observed directly over the volcano. The satellite overpass was about 75 minutes after a short, but explosive eruption. This cloud was near our level of detection, containing only 10 kt SO:. Except for the March 9 eruption, no SO2 was observed by TOMS from any of the 12 major explosive eruptions after December 15. The ultraviolet light level was insufficient for measurement directly over the volcano until early March,
Table 1 Major eruptions of Redoubt Volcano ( 1989-1990 ) Day
*Time (Duration)
*Plume height, Azimuth
Dec 14 Dec 15
0947 0140 0348 1015 0630 1748 1927 1009 2248 0410 2039 0951 0947 0404 1033 1449
> 10, NE ? 9 > 12, NNE >9, ? > 12, NNE > 12, NNE > 12, ESE >II,NNE > 10, SE 12, NNE 10, WSW 12, NE > 10, NE ?, NNE > 10, NW
Dec 19 Jan 2 Jan 8 Jan 16 Feb 15 Mar4 Mar9 Mar 14 Mar 23 Mar29 Apr 15
(17) (12) (10) (40) (9) (26) (6l) (15) (13) (20) (8) (10) (14) (8) (7) (8)
TOMS data examined
SO2 detected
12/14-12/18
YES: 12/16. 12/17
12/19-12/21 1/3, 1/4
NO NO
1/9, 1/10 1/17, 1/18 2/15, 2/16 3/5, 3/6 3/9, 3/10 3/14, 3/15 3/23, 3/24 3/29, 3/30 4/16, 4/17
NO NO NO NO YES: 3/9 NO NO NO NO
* Time is Alaska Standard Time. Duration is minutes of explosive activity based on seismic record. Plume height is above sea level. Data from Brantley (1990).
C.C. Schnetzler et al. I Journal of Volcanology and Geothermal Research 62 (1994) 353-35 7 --'~,,'/
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Fig. 1. TOMS SO2 image of North America on December 16, 1989, showing a cloud over western Nevada and eastern California. The filled circle is the site of Redoubt Volcano, and the approximate path of the cloud from the volcano to its location on 16 December is shown by the heavy dashed line. Background values, below 10 milliatmosphere-cm, have been supressed (mean value of 1 matm-cm is approximately 0.1 kt SO2). Numbers and letters show the SO2 level in a pixel: 0 = I 1- 15 matm-cm, 1 = 1620 matm-cm; 2 = 2 1 - 2 5 matm-cm, etc. (A, B, C, etc. follow 9). Scattered pixels over southeastern Canada and eastern U.S. are due to high ozone which were not fully separated from SO2. Data were not collected above about 58°N due to low ultraviolet light level in mid-winter.
and wind directions on two of the 5 days of major eruptions between December 19 and February 15 (Table 1 ) would relatively quickly carry a cloud southward to sufficient light level. But on the other three days, clouds would have had to take a longer path to the north and then turn to the south before we could observe them, sim-
ilar to the cloud which was observed on December 16, or the winds may never have taken the clouds southward enough to bring them into view with TOMS. Thus, because of low light level and northern wind directions, we cannot speculate on the amounts of SO2 produced by the December 19, January 2, and January 16 eruptions.
356
C. C Schnetzler et aL / Jounrat of Volcanology and Geothermal Research 62 (1994) 353-35 7
3. Discussion From the amount of S O 2 observed on December 16 it is possible to estimate the approximate amount of SO2 erupted, given knowledge of the time of eruption and the dissipation rate of SO2 in the atmosphere. Unfortunately, we do not have precise knowledge about either the time or dissipation rate. The SO2 cloud observed on December 16 is unique in our experience in that TOMS first detected the cloud thousands of kilometers from its source. We are confident the cloud was the result of an explosive eruption at Redoubt Volcano, as winds over North America during this period would carry a Redoubt cloud over the observed region, and there was no other reported eruption in the hemisphere at that time. However, as there were four major explosive eruptions within 50 hours prior to the observation, we can not definitively associate this cloud with one particular eruption. We do not think it came from the December 14 eruption. If it had originated from this initial eruption and had followed the anticipated path (see Fig. 1 ), it should have been observed on December 15 over western Canada south of the terminator (the latitude above which TOMS cannot measure SO2 due to low ultraviolet light level). Since no cloud was observed on the December 15 overpass, the cloud observed on December 16 probably did not come from the eruption on the 14th. However, we cannot exclude any of the three early morning eruptions on the 15th by the same reasoning as there was insufficient time for the cloud to travel northward and then back south of the terminator in the short time before the noon pass on the 15th. Thus, the time between eruption on the 15th and our observation at noon on the 16th is from 26 to 34 hours. We lean toward the smaller number due to the longer duration of the 1015 hr eruption. This cloud was apparently injected into the atmosphere near the tropopause (Table 1). In other eruptions we have studied, cloud movements have been used to indicate altitudes of cloud emplacement (Krueger, 1983; Krueger et al., 1990), as wind velocities and directions usually differ at different altitudes. However, the
winds on December 15 were approximately the same intensity and direction at all altitudes, and it was not possible to use the movement of this cloud as an indication of its altitude. The compactness of the cloud, as well as its apparent structure (Fig. 1, inset) after such a long journey, suggests emplacement of the SO2 within a limited altitude range. The rapid northward and then southward movement of the cloud indicates it was entrapped into the jet stream, which at this time swept down to the southwest U.S., and then turned and went eastward across the southern U.S. When the jet stream decelerated and turned over southwestern U.S., the volcanic cloud left the jet stream (on the same side as the cloud entered it), and rapidly dissipated, dropping from ! 00 kt on the 16th to 30 kt on the 17th, and then to below the detection limit of ~ 10 kt on the 18th. The speed also dropped as the cloud left the jet stream, from ~ 175 km/hr, averaged from the time of eruption to noon on December 16, to ~ 50 k m / h r between noon on the l6th and noon on the 17th. During the approximately 4500-km trip from the eruption to its detection over California and Nevada about 26 hours later, this cloud spent only a few hours in sunlight (a necessary ingredient to drive the conversion of SO2 tO H2804). During the afternoon of the 15th it was above the terminator, due to the initial northward movement, and then it was in darkness during the night of December 15/16. Thus, dissipation of the SO2 cloud probably only increased significantly soon before our observation at noon on the 16th. Given all the unknowns, our best approximation to the amount of SO2 produced by the 1015 eruption on December 15 is 175 +_50 kt. Due to the high north latitude of Redoubt Volcano and the winter dates of over half of its major eruptions, TOMS was unable to put constraints on the amount of SO2 produced by some of these events. However, this eruption was unique and interesting in that the cloud was observed so far from the source, and it does illustrate TOMS' utility in tracking potentially hazardous SO2 clouds as well as in wind trajectory analysis.
C. C Schnetzler et al. / Journal of Volcanology and Geothermal Research 62 (1994) 353-35 7
Acknowledgements We wish to thank J. Sissala and members of the GE/RCA service group for providing a short turn-around on Nimbus 7 data, and J. Williams of Hughes STX and A. Oakes of GSFC for promptly responding to our request for near-realtime satellite data processing. References Alaska Volcano Observatory Staff, 1990. The 1989-1990
357
eruption of Redoubt Volcano. EOS, Trans. Am. Geophys. Union, 71: 265-275. Brantley, S.R. (Editor), 1990. The Eruption of Redoubt volcano, Alaska, December 14, 1989-August 31, 1990. U.S. Geol. Surv., Circular 1061:33 pp. Krueger, A.J., 1983. Sighting of El Chichon sulfur dioxide clouds with the Nimbus 7 Total Ozone Mapping Spectrometer. Science, 220:1377-1379. Krueger, A.J., Walter, L.S., Schnetzler, C.C. and Doiron, S.D., 1990. TOMS measurement of the sulfur dioxide emitted during the 1985 Nevado del Ruiz eruptions. In: S.N. Williams (Editor), Nevado del Ruiz, I. J. Volcanol. Geotherm. Res., 41: 7-15.
Journal of Volcanologyand Geothermal Research 62 (1994) 353-357
Satellite measurement of sulfur dioxide from the Redoubt eruptions of 1989-1990 C.C. Schnetzler a, S.D. D o i r o n b, L.S. Walter a, A.J. Krueger ~ aEarth Sciences Directorate, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA bHughes STX Corporation, Lanham, MD, USA Received 9 May 1991; accepted 20 September 1993
Abstract
The mass of SO2 emitted by the 16 major explosive eruptions of Redoubt Volcano between December 1989 and April 1990 have been examined by the Total Ozone Mapping Spectrometer (TOMS) carried on the Nimbus 7 satellite. Because of low light levels during the winter months, TOMS could not detect SO2 at high northern latitudes. Thus, the major eruptions from December through February could not be monitored unless winds brought the clouds to latitudes lower than about 58°N. Only two SO2 clouds were observed in the satellite data - - an approximately 100-kiloton (kt) cloud on December 16 over Nevada and eastern California, and a 10-kt cloud on March 9 directly over the volcano. We speculate that the major eruption on December 15 at 1015 hour produced the 100-kt cloud seen on December 16, and the mass of SO2 injected into the atmosphere at that time was 175 + 50 kt.
1. Introduction
During the four-month period, from mid-December 1989 to mid-April 1990, Redoubt Volcano, Alaska experienced a number of short explosive eruptions (Alaska Volcano Observatory Staff, 1990; Brantley, 1990; see Table 1 ). We have used data from the Total Ozone Mapping Spectrometer (TOMS) carded on the Nimbus 7 satellite to measure SO2 emitted by these explosive eruptions of Redoubt Volcano. As the name denotes, TOMS was designed to measure atmospheric ozone; however, it was discovered during the 1982 eruption of E1 Chichon that SO2 is also detectable by this sensor. TOMS records the absorption of ultraviolet light by ozone and SO2, and differential absorption in TOMS' six ultraviolet bands allows separation of these two gases
(Krueger, 1983). The instrument has a maxim u m spatial resolution (pixel size) of 50 km at nadir and an average resolution across the scan of 66 km. The noise level for an average size single pixel is about 500 metric tons (0.5 kt) SO2. However, background variation (zero offset range) is about 1 or 2 kt. We consider this the detection limit per pixel, but as a cloud is defined as several contiguous pixels above background variation, our cloud detection limit is about 5 to 10 kt. The Nimbus 7 orbit and TOMS swath width provide daily global coverage, with an approximately noon local time overpass. We have examined the satellite data taken on, and for several days subsequent to, the date of major Redoubt explosive eruptions. The dates of the explosive eruptions and the dates we searched the TOMS data for SO2 clouds are given in Table
0377-0273/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSD10377-0273 (93) E0100-G
354
C C. Schnetzler et al. / Jounra/ ~?/ Volcanology and Geothermal Research 62 (1 t)94) 353-35 7
1. During the winter months TOMS could not record data directly over Redoubt Volcano (latitude 60.4 °N) due to insufficient ultraviolet light levels above about 58 ° to 60°N. Wind patterns on some of the days we examined, however, were to the south and east, either directly or after a relatively minor excursion to the north, so that any SO2 cloud should be brought southward into the area of detectability. By early March the ultraviolet light level was sufficient to obtain data as far north as 65 °.
2. Observations For the 16 reported major eruptions of Redoubt Volcano on 13 days between December 14, 1989 and April 15, 1990 (Table 1 ), we detected only two SO2 clouds. The larger of these two clouds was observed on December 16 and 17. Figure 1 shows the SO2 cloud on December 16, with an area of about 120,000 square kilometers, located over Nevada and eastern California. The quantity of SO2 can be calculated by integrating the column SO2 amounts across the cloud and correcting for background amounts (Krueger,
1983; Krueger et al., 1990 ). On this day the cloud contained 100 ( + 15 ) kt of SO2. On December 15, the winds at all altitudes over North America, as determined from National Meteorology Center data, were strong to the north over Redoubt Volcano, turning eastward at about 70 ° N, and then in a southeastern direction over western Canada and western United States (Fig. 1 ). Thus, the cloud observed on December 16 had traveled approximately 4500 km from the volcano to Nevada. Twenty-four hours later, on December 17, the cloud had traveled an additional 1100 km to off the coast of Baja California. At this time the cloud contained only about 30 kt SO2. The cloud dissipated below the detection limit by the time of overpass on December 18. On March 9, 1990 a small, four-pixel SO2 cloud was observed directly over the volcano. The satellite overpass was about 75 minutes after a short, but explosive eruption. This cloud was near our level of detection, containing only 10 kt SO:. Except for the March 9 eruption, no SO2 was observed by TOMS from any of the 12 major explosive eruptions after December 15. The ultraviolet light level was insufficient for measurement directly over the volcano until early March,
Table 1 Major eruptions of Redoubt Volcano ( 1989-1990 ) Day
*Time (Duration)
*Plume height, Azimuth
Dec 14 Dec 15
0947 0140 0348 1015 0630 1748 1927 1009 2248 0410 2039 0951 0947 0404 1033 1449
> 10, NE ? 9 > 12, NNE >9, ? > 12, NNE > 12, NNE > 12, ESE >II,NNE > 10, SE 12, NNE 10, WSW 12, NE > 10, NE ?, NNE > 10, NW
Dec 19 Jan 2 Jan 8 Jan 16 Feb 15 Mar4 Mar9 Mar 14 Mar 23 Mar29 Apr 15
(17) (12) (10) (40) (9) (26) (6l) (15) (13) (20) (8) (10) (14) (8) (7) (8)
TOMS data examined
SO2 detected
12/14-12/18
YES: 12/16. 12/17
12/19-12/21 1/3, 1/4
NO NO
1/9, 1/10 1/17, 1/18 2/15, 2/16 3/5, 3/6 3/9, 3/10 3/14, 3/15 3/23, 3/24 3/29, 3/30 4/16, 4/17
NO NO NO NO YES: 3/9 NO NO NO NO
* Time is Alaska Standard Time. Duration is minutes of explosive activity based on seismic record. Plume height is above sea level. Data from Brantley (1990).
C.C. Schnetzler et al. I Journal of Volcanology and Geothermal Research 62 (1994) 353-35 7 --'~,,'/
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Fig. 1. TOMS SO2 image of North America on December 16, 1989, showing a cloud over western Nevada and eastern California. The filled circle is the site of Redoubt Volcano, and the approximate path of the cloud from the volcano to its location on 16 December is shown by the heavy dashed line. Background values, below 10 milliatmosphere-cm, have been supressed (mean value of 1 matm-cm is approximately 0.1 kt SO2). Numbers and letters show the SO2 level in a pixel: 0 = I 1- 15 matm-cm, 1 = 1620 matm-cm; 2 = 2 1 - 2 5 matm-cm, etc. (A, B, C, etc. follow 9). Scattered pixels over southeastern Canada and eastern U.S. are due to high ozone which were not fully separated from SO2. Data were not collected above about 58°N due to low ultraviolet light level in mid-winter.
and wind directions on two of the 5 days of major eruptions between December 19 and February 15 (Table 1 ) would relatively quickly carry a cloud southward to sufficient light level. But on the other three days, clouds would have had to take a longer path to the north and then turn to the south before we could observe them, sim-
ilar to the cloud which was observed on December 16, or the winds may never have taken the clouds southward enough to bring them into view with TOMS. Thus, because of low light level and northern wind directions, we cannot speculate on the amounts of SO2 produced by the December 19, January 2, and January 16 eruptions.
356
C. C Schnetzler et aL / Jounrat of Volcanology and Geothermal Research 62 (1994) 353-35 7
3. Discussion From the amount of S O 2 observed on December 16 it is possible to estimate the approximate amount of SO2 erupted, given knowledge of the time of eruption and the dissipation rate of SO2 in the atmosphere. Unfortunately, we do not have precise knowledge about either the time or dissipation rate. The SO2 cloud observed on December 16 is unique in our experience in that TOMS first detected the cloud thousands of kilometers from its source. We are confident the cloud was the result of an explosive eruption at Redoubt Volcano, as winds over North America during this period would carry a Redoubt cloud over the observed region, and there was no other reported eruption in the hemisphere at that time. However, as there were four major explosive eruptions within 50 hours prior to the observation, we can not definitively associate this cloud with one particular eruption. We do not think it came from the December 14 eruption. If it had originated from this initial eruption and had followed the anticipated path (see Fig. 1 ), it should have been observed on December 15 over western Canada south of the terminator (the latitude above which TOMS cannot measure SO2 due to low ultraviolet light level). Since no cloud was observed on the December 15 overpass, the cloud observed on December 16 probably did not come from the eruption on the 14th. However, we cannot exclude any of the three early morning eruptions on the 15th by the same reasoning as there was insufficient time for the cloud to travel northward and then back south of the terminator in the short time before the noon pass on the 15th. Thus, the time between eruption on the 15th and our observation at noon on the 16th is from 26 to 34 hours. We lean toward the smaller number due to the longer duration of the 1015 hr eruption. This cloud was apparently injected into the atmosphere near the tropopause (Table 1). In other eruptions we have studied, cloud movements have been used to indicate altitudes of cloud emplacement (Krueger, 1983; Krueger et al., 1990), as wind velocities and directions usually differ at different altitudes. However, the
winds on December 15 were approximately the same intensity and direction at all altitudes, and it was not possible to use the movement of this cloud as an indication of its altitude. The compactness of the cloud, as well as its apparent structure (Fig. 1, inset) after such a long journey, suggests emplacement of the SO2 within a limited altitude range. The rapid northward and then southward movement of the cloud indicates it was entrapped into the jet stream, which at this time swept down to the southwest U.S., and then turned and went eastward across the southern U.S. When the jet stream decelerated and turned over southwestern U.S., the volcanic cloud left the jet stream (on the same side as the cloud entered it), and rapidly dissipated, dropping from ! 00 kt on the 16th to 30 kt on the 17th, and then to below the detection limit of ~ 10 kt on the 18th. The speed also dropped as the cloud left the jet stream, from ~ 175 km/hr, averaged from the time of eruption to noon on December 16, to ~ 50 k m / h r between noon on the l6th and noon on the 17th. During the approximately 4500-km trip from the eruption to its detection over California and Nevada about 26 hours later, this cloud spent only a few hours in sunlight (a necessary ingredient to drive the conversion of SO2 tO H2804). During the afternoon of the 15th it was above the terminator, due to the initial northward movement, and then it was in darkness during the night of December 15/16. Thus, dissipation of the SO2 cloud probably only increased significantly soon before our observation at noon on the 16th. Given all the unknowns, our best approximation to the amount of SO2 produced by the 1015 eruption on December 15 is 175 +_50 kt. Due to the high north latitude of Redoubt Volcano and the winter dates of over half of its major eruptions, TOMS was unable to put constraints on the amount of SO2 produced by some of these events. However, this eruption was unique and interesting in that the cloud was observed so far from the source, and it does illustrate TOMS' utility in tracking potentially hazardous SO2 clouds as well as in wind trajectory analysis.
C. C Schnetzler et al. / Journal of Volcanology and Geothermal Research 62 (1994) 353-35 7
Acknowledgements We wish to thank J. Sissala and members of the GE/RCA service group for providing a short turn-around on Nimbus 7 data, and J. Williams of Hughes STX and A. Oakes of GSFC for promptly responding to our request for near-realtime satellite data processing. References Alaska Volcano Observatory Staff, 1990. The 1989-1990
357
eruption of Redoubt Volcano. EOS, Trans. Am. Geophys. Union, 71: 265-275. Brantley, S.R. (Editor), 1990. The Eruption of Redoubt volcano, Alaska, December 14, 1989-August 31, 1990. U.S. Geol. Surv., Circular 1061:33 pp. Krueger, A.J., 1983. Sighting of El Chichon sulfur dioxide clouds with the Nimbus 7 Total Ozone Mapping Spectrometer. Science, 220:1377-1379. Krueger, A.J., Walter, L.S., Schnetzler, C.C. and Doiron, S.D., 1990. TOMS measurement of the sulfur dioxide emitted during the 1985 Nevado del Ruiz eruptions. In: S.N. Williams (Editor), Nevado del Ruiz, I. J. Volcanol. Geotherm. Res., 41: 7-15.