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Gravity, deformation and the Earth's crust
a t t e n t i o n to d e t a i l e d c o n t i n uous- profiling techniques than their American counterparts, and this has enabled t h e m to e x a m i n e t h e s t r u c t u r e of t h e s e d i m e n t a r y l a y e r s a n d t h e s u r f a c e of c r y s t a l l i n e b a s e m e n t in c o n j u n c t i o n with s e i s m i c s o u n d i n g of the d e e p e r c r u s t a l l a y e r s and t h e M- d i s c o n t i n u i t y . E x c e l l e n t e x a m p l e s o~ r e s u l t s o b t a i n e d by Soviet g e o p h y s i c i s t s a r e c o n t a i n e d in two p a p e r s on d e e p s e i s m i c s o u n d i n g in t h e B l a c k Sea d e p r e s s i o n . T h e f i r s t of t h e s e (Deep s e i s m i c s o u n d i n g of t h e e a r t h ' s c r u s t in t h e c e n t r a l p a r t of t h e B l a c k Sea d e p r e s s i o n , by Yu. P. Neprochnov, A.F. Neprochnova,I S.M. S v e r e v a n d V.I. M i r o n o va, p p . 4 9 - 7 8 ) d e s c r i b e s a n d p r e s e n t s t h e r e s u l t s of a n onshore-offshore experiment r e m a r k a b l y like t h e j o i n t U . S . - C a n a d a e x p e r i m e n t s in the Lake Superior region.The second (Results from records o b t a i n e d by r e g i o n a l s e i s m i c stations during deep seismic s o u n d i n g in t h e B l a c k Sea, by S.M. Z v e r o v a n d V.I. M i r o n o v a , p p . 7 9 - 9 1 ) is r e m i n i s c e n t of the u s e of e a r t h q u a k e s e i s m i c n e t w o r k s by C a l i f o r n i a s e i s m o l o g i s t s to study crustal structure. Other papers discuss recording with intermediate magnetic tape (A.N. Fursov and G.A.Yaroshevskaya), the surface of crystalline basement (N.P. Ivanova), dependence of the intensity and spectrum of seismic waves on charge size (G.G. Mikhota), grouped shot holes for deep seismic sounding (G.G. Mikhota and Yu. V. Tulina), study of sedimentary layers in deep seismic sounding atsea (S.M. Zverev), propagation of airy waves in shallowwater (E.A. Starshinova), and determination of distances and depths in operations at sea (E .A. Star shinova). In his preface to the Russian edition (published in 1965) Zverev notes that the majority of the papers in this volume were written by young authors just be-
ginning independent research. Judging from the quality of these papers, the future of Soviet deep seismic sounding is in good hands. The price of the Consultants Bureau translation(U.S. $22.50) will discourage many young researchers from buying this volume. I hope, however, that every serious student of the earth's crust will have Problems in Deep S e i s m i c Sou~Ming a v a i l a b l e in h i s i n s t i t u t i o n ' s r e f e r e n c e l i b r a r y , on h i s own b o o k s h e l v e s , o r in h i s c o l l e a g u e ' s office down t h e hall. L.C. Pakiser REFERENCES S t e i n h a r t , J.S. a n d M e y e r , R . P . , 1961. E x p l o s i o n s t u d i e s of c o n t i n e n t a l s t r u c t u r e .
Carnegie Inst. Wash. Publ., 6 2 2 : 4 0 9 pp. Pakiser, L.C. and S t e i n h a r t , J . S . , 1964. E x p l o s i o n s e i s m o l o g y in t h e W e s t e r n H e m i s p h e r e . In: H. Odishaw (Editor), Research
in g e o p h y s i c s , 2. Solid Earth and Interface Phenomeua. Mass. Inst. Technol. Press, Cambridge, Mass. pp.123-147. i
Tectonic Model Experiments H. R a m b e r g , 1967. Gravity,
Deformation and the Earth's Crust. A c a d e m i c P r e s s , L o n d o n , 214 pp., 116 f i g . , 9 p l a t e s , 75 a 6 d . T h i s book s h o u l d b e r e g a r d ed a s a m i l e - s t o n e in t e c t o n i c m o d e l e x p e r i m e n t s . It is the first time someone has t a k e n a d v a n t a g e of t h e p o s s i b i l i t y , k n o w n in p r i n c i p l e f o r a l o n g t i m e , of m a k i n g e x p e r i m e n t s in a c e n t r i f u g e m a c h i n e . T h e i n c r e a s e of gravity thus compensates partially for the tremendous m a g n i t u d e of t h e l e n g t h s c a l e , and p e r m i t s t h e u s e of model-building material which has strength enough for c o n v e n i e n t h a n d l i n g and, m o s t i m p o r t a n t of all, e a s y
s t u d y of s h a p e s a f t e r t h e experiment. A c o n s i d e r a b l e a m o u n t of w o r k h a s b e e n s p e n t to b u i l d a centrifuge machine producing a c c e l e r a t i o n s up to 2,900 x g, a n d to s e l e c t a v a r i e t y of m a t e r i a l s with d i f f e r e n t s t r e n g t h s , d e n s i t i e s and colo u r s . A g r e a t n u m b e r of e x periments have been carefully p l a n n e d a n d c a r r i e d out and t h e i r r e s u l t s h a v e b e e n a n a l y s e d and r e c o r d e d by good photographs. It is a pity t h a t c o m p a r a b l e c a r e h a s n o t b e e n t a k e n to make a reliable, correct, mathematical analysis, although such mathematical t r e a t m e n t is f u n d a m e n t a l to a c o r r e c t i n t e r p r e t a t i o n of scale model experiments. The a u t h o r i g n o r e s t h e v e r y fund a m e n t a l s of m e c h a n i c a l a n a lysis, which have been classical for m o r e t h a n a c e n t u r y . The t h e o r y e x p o s e d in t h e f i r s t 40 p a g e s of t h e book, a l t h o u g h c r o w d e d with m a t h e m a t i c a l f o r m u l a s , is nothing more than the formul a t i o n of v a g u e i n t u i t i o n s , a n d is, f r o m a m a t h e m a t i c a l p o i n t of v i e w , q u i t e i n c o n s i s tent. The author uses a " s h a p e p o t e n t i a l " w h i c h is not a potential, ignores the mat h e m a t i c a l d e f i n i t i o n of s t r e s s w h i c h is m i x e d up with v o l u m e f o r c e s (eq.5, p.4), u s e s the t i m e s c a l e of d y n a m i c s (p.38) i n s t e a d of the s t a t i c t i m e s c a l e a l t h o u g h he h a d j u s t s h o w n it w a s not r e l e v a n t . It would be too l e n g t h y to p o i n t out h e r e all the c o r r e c t i o n s t h a t s h o u l d be m a d e to t h e w h o l e o{* the f i r s t five chapters. T h e r e s u l t of t h i s i n e x p l i c a b l e f a i l u r e of the m a t h e m a t i c a l t r e a t m e n t is t h a t the d i s t i n c t i o n b e t w e e n the two q u i t e d i f f e r e n t s o r t s of s i m i l a r i t y of v i s c o s i t y a n d p l a s t i city (the l a t e r with a f i n i t e y i e l d s t r e s s ) is not m a d e . Without e v e n b e i n g a w a r e of it, t h e a u t h o r u s e s the v i s c o s i t y m o d e l . It s e e m s to m e likely t h a t t h e p l a s t i c i t y e q u a t i o n s would be m u c h c l o s e r to t h e a c t u a l p r o p e r t i e s of r o c k s , a s well a s to
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the m a t e r i a l s u s e d in the e x p e r i m e n t s . But the data that would be n e c e s s a r y for an i n t e r p r e t a t i o n following the laws of p l a s t i c i t y a r e lacking. T h u s d e s p i t e the a u t h o r ' s intention, t h e s e e x p e r i m e n t s cannot be taken a s giving quantitative results. Their value is chiefly to appeal to the i m a g i n a t i o n , a n d to s u g g e s t tectonic s h a p e s and p r o c e s s e s . E v e r y geologist i n t e r e s t e d in t e c t o n i c s should e x a m i n e with deep i n t e r e s t the p i c t u r e s of m o d e l s def o r m e d in the c e n t r i f u g e m a c h i n e , and s o m e of t h e s e p i c t u r e s m a y well b e c o m e c l a s s i c a l . But t h i s does not m e a n that all the a u t h o r ' s c o n c l u s i o n s will be accepted. His m a c h i n e allows only the study of g r a v i t a t i o n a l r e a d j u s t m e n t for a l a y e r s e q u e n c e in which density does not a l w a y s i n c r e a s e t o w a r d s the bottom; it does not d i r e c t l y p r o d u c e a l a t e r a l c o m p r e s s i o n . But, it is c l e a r that t h i s is not a r e a s o n to deny that s u c h p r o c e s s e s m a y play a p a r t in actual tectonic d e f o r m a t i o n s . Along t h i s p r i n c i p l e , a n u m b e r of e x p e r i m e n t s have been p e r f o r m e d and although their g e n e r a l s e t t i n g is r a t h e r similar, interpretations are given in which i n c r e a s i n g s c a l e s of d i m e n s i o n a r e a s s u m e d a s m o d e l s for m o r e and m o r e e x t e n s i v e phenom e n a , even though the s p e e d of r o t a t i o n and, thus, the c e n t r i f u g a l f o r c e , is about the s a m e . After a c h a p t e r devoted to e x p e r i m e n t s not u s i n g the centrifuge machine, a first s e q u e n c e of c e n t r i f u g e exper i m e n t s a r e taken a s r e p r e s e n t i n g s a l t p l u g s , or s a l t d o m e s . T h i s is s u r e l y the most easily reproduceable s t r u c t u r e , s i n c e no f o r c e other than g r a v i t y is at work. The d i s c u s s i o n gives i n t e r e s t i n g indications of the d i s t a n c e between n e i g h b o u r ing d o m e s a s r e l a t e d to the t h i c k n e s s of the s a l t l a y e r , of the m a r g i n a l s i n k and of the n a t u r e of s t r a i n of the
s a l t d o m e itself. T h i s is a p o s i t i v e r e t u r n on c e n t r i f u g e e x p e r i m e n t s , but it should be pointed out that s o m e of t h e s e r e s u l t s can be obtained by t h e o r e t i c a l m e c h a n i c a l analysis. Another s e t of e x p e r i m e n t s is d e s i g n e d to study the int r u s i o n of a m o l t e n m a g m a which is l i g h t e r than the s u r r o u n d i n g r o c k s . The m a g m a is r e p r e s e n t e d by an a q u e o u s solution which s t a i n s the path it follows. Such exper i m e n t s can r e p r e s e n t only mechanical effects, however, and one could wonder if t h e r m a l e f f e c t s , s u c h a s vap o r i z a t i o n of w a t e r , do not play an i m p o r t a n t r o l e in actual m a g m a t i c i n t r u s i o n s . Other e x p e r i m e n t s , a l w a y s with d e n s e l a y e r s at the top, differ in the l a t e r a l e x t e n s i o n of t h e s e d e n s e l a y e r s , or s o m e v a r i a t i o n s in the d i s t r i bution of s t r e n g t h . T h e r e is no r e a l d i f f e r e n c e between the s i n k i n g of a heavy l a y e r and the r i s e of a buoyant deep l a y e r . One of the m o s t int e r e s t i n g f e a t u r e s of t h e s e e x p e r i m e n t s is that when t h e r e is a light l a y e r at the top, it m a y be l a t e r a l l y c o m p r e s s e d by the m a t t e r r i s i n g f r o m beneath and o v e r r i d d e n by a m o r e d e n s e l a y e r . Some p i c t u r e s of s e c t i o n s of s u c h models featuring rising d o m e s with lobate s t r u c t u r e s c o m i n g f r o m the depth and s p r e a d i n g over a d e n s e l a y e r , show a r a t h e r s t r i k i n g s i m i l a r i t y to c l a s s i c a l s e c t i o n s of alpine n a p p e s . But it is difficult to a c c e p t a s i m i l a r o r i gin, s i n c e the deep buoyant m a t t e r would not likely be of s e d i m e n t a r y origin, as a r e the alpine n a p p e s . Such e x p e r i m e n t s which d e m o n s t r a t e the r i s e of a deep buoyant l a y e r a r e a l s o taken a s m o d e l s for g r a n i t i c i n t r u s i o n . Since g r a v i m e t r y h a s provided e v i d e n c e for the low d e n s i t y of g r a n i t i c i n t r u s i o n s , I feel the geological i m p l i c a t i o n s of t h i s fact h a v e not yet r e c e i v e d s u f f i cient attention. P r o f e s s o r R a m b e r g ' s ideas about the r o l e played by g r a v i t y buoy-
ancy in g r a n i t i c i n t r u s i o n s , and the r e l a t e d model experiments, deserve serious c o n s i d e r a t i o n . They draw attention to i n t e r e s t i n g c o m p a r i s o n s between field occ u r r e n c e s of acid and b a s i c r o c k s with e x a m p l e s taken from the Scandinavian Caledonides. At a still larger scale, some experiments are taken as models for convection currents in the mantle, it should be pointed out that the author does not make a clearcut distinction between crust and mantle, and this may well be wise. But, these models of deep-seated convection c u r rents clearly produce these lateral compressions in the upper layers which were ruled out by the author when he was studying superficial layers alone (see, for instance fig.t12). Perhaps because an accurate mechanical analysis is lacking, the author takes no account of the outer surface shape, although it must play an important part in any gravitational settling, as can easily be shown for salt domes. In some of the experiments which are assumed to provide models for the largest features, there is, on top of the model, a light l a y e r of " s o f t wax" or "oilwax m i x t u r e " with a v e r y l o w s t r e n g t h . T h e r e is no explanation as to the r o l e this l a y e r is s u p p o s e d to playr In fact, it r e d u c e s the effect of the d e n s i t y of the next l a y e r , in c o m p a r i s o n to the d i f f e r e n c e s of d e n s i t y between d i f f e r e n t l a y e r s . But the anal y s i s of the effect it h a s on the s h a p e of the s u r f a c e is lacking. The a u t h o r h a s put m o r e s t r e s s on v e r t i c a l s e c t i o n s of m o d e l s than on a r e a l d i s tribution of d e f o r m a t i o n s (although the p i c t u r e on the cover of the book shows one of these). In fact, this d i s t r i bution of c o m p r e s s i o n and e x t e n s i o n is too c l o s e l y r e l a t e d to the s e t t i n g of exp e r i m e n t s to give m u c h inf o r m a t i o n , be it of the c i r -
c u l a r e x t e r n a l s h a p e , or t h e s h a p e g i v e n to t h e l a y e r s w h i c h do not e x t e n d to t h e whole model. N e v e r t h e l e s s , I t h i n k t h i s is t h e d i r e c t i o n in w h i c h n e w r e s e a r c h s h o u l d be c a r r i e d on with t h e a u t h o r ' s c e n t r i fuge m a c h i n e . T h i s v e r y efficient device has been u s e d f o r t h e s t u d y of one peculiar tectonic phenomenon, g r a v i t a t i o n a l s u b s i d e n c e . It c a n a l s o be u s e d f o r t h e s t u d y of l a t e r a l c o m p r e s s i o n of s t r a t i f i e d l a y e r s by u s i n g some devices such as the one s h o w n in fig.25 and 26. I am sure such experiments could bring very interesting r e s u l t s , e s p e c i a l l y if an u p to-date mathematical treatm e n t is a p p l i e d . I a m a w a i t ing with d e e p i n t e r e s t a l a t e r book in w h i c h s u c h e x p e r i m e n t s will b e r e c o r d e d . -
J. Goguel
Classic Work on Continental Drift A. W e g e n e r , 1966. The Origin o f Continents and Oceans ( E n g l i s h t r a n s l a t i o n of 4th G e r m a n r e v i s e d e d i t i o n , 1929). D o v e r P u b l i c a t i o n s , New Y o r k , N.Y., 246 pp., 64 fig., U.S.
$~.00. T h e t h e o r y of c o n t i n e n t a l d r i f t h a s f o r m e d a p a r t of g e o l o g i c a l t h o u g h t s i n c e its initial c o n c e p t i o n . F r a n c i s B a c o n (1620), Von H u m b o l d t (1800), Owen (1857), S n i d e r (1858), F i s h e r (1881, 1889), P i e k e r i n g (1907), T a y l o r (1910), B a k e r (1911) a r e s o m e of t h e n a m e s m e n t i o n e d in p r o f e s s i o n a l l i t e r a t u r e in this connection. But it w a s A l f r e d W e g e n e r (1912-1928) who s u c c e e d e d in g a i n i n g w i d e s p r e a d a t t e n tion a n d s u p p o r t f o r t h i s c o n c e p t by b r i n g i n g p a l a e o climatic and other diagnostic f a c t s a s e v i d e n c e to b e a r on it. B e c a u s e of t h e f e e b l e m e c h a n i s m f o r d r i f t to w h i c h Wegener resorted as a mec h a n i c a l e x p l a n a t i o n , how-
ever, there was and still is resistance among many earth- scientists to accepting this concept as a basic principle in the geodynamic evolution of the earth's crust (e.g., Beloussov). In the old controversy between fixism and mobilism (the static and the dynamic models of crustal evolution), a new scientific tool, palaeomagnetism, has recently brought forward independent (diagnostic) facts. Consequently, discussions about d r i f t h a v e f l a r e d up a g a i n .
In t h e s e d i s c u s s i o n s m a n y authors quote Wegener's w o r k Entstehung der Kontinente without h a v i n g b e e n able to rea,~ the G e r m a n text. T h e r e f o r e , he is often m i s represented. T h e i n t i t i a t i v e to m a k e t h i s c l a s s i c e a s i l y a v a i l a b l e to English speaking and reading earth scientists is, therefore, a v e r y w e l c o m e one. T h e t r a n s l a t i o n by J o h n B i r a m is e x c e l l e n t a n d t h e p r i c e of t h i s p a p e r b a c k e d i t i o n is reasonable. R.W. van Bemmelen
Uniformitarianism, Catastrophism and Christian Faith D.W. P a t t e n , 1966. The Biblical Flood and the Ice Epoch. - P a c i f i c M e r i d i a n Publ. Co., S e a t t l e , W a s h . , 336 pp., 27 fig., 13 t a b l e s , U.S. $ 7.50. F r o m t h e m o m e n t t h a t t h e o r i e s of e v o l u t i o n and u n i f o r m i t a r i a n i s m w e r e i n t r o d u c e d to the s c i e n t i f i c w o r l d , t h e r e h a v e b e e n p e o p l e r e j e c t i n g t h e s e v i e w s . S e v e r a l did s o b e c a u s e t h e y felt t h e y h a d to d e f e n d t h e i r C h r i s t i a n faith a g a i n s t t h e p o s t u l a t e s of s c i e n c e . T o t h e s e p e o p l e , t w o m a i n w a y s w e r e o p e n t o f i g h t t h e m a i n s t r e a m of s c i e n t i f i c d e v e l o p m e n t . One a l t e r n a tive w a s s i m p l y to r e j e c t what s c i e n t i s t s s a i d a b o u t e v o l u t i o n and t h e h i s t o r y of t h e e a r t h . T h e o t h e r w a s to p r o d u c e a l t e r n a tive t h e o r i e s of e v o l u t i o n a n d u n i f o r m i t a r i a n i s m . A m o n g t h o s e who a d o p t e d t h e l a t t e r c o u r s e is t h e s m a l l g r o u p of t h e s o c a l l e d c a t a s t r o p h i s t s . M o s t , b u t not all, of t h e s e p e o p l e c a m e f r o m s m a l l and c o n s e r v a t i v e P r o t e s t a n t c i r c l e s . In 1886, I s a a c Newton Vail, a Q u a k e r , p u b l i s h e d a book, The Waters aboz~e the F i r m a ment, in w h i c h h e l a u n c h e d his theory that each planet p a s s e d t h r o u g h a p h a s e in w h i c h it h a d a r i n g s i m i l a r to S a t u r n ' s . In the c a s e of our earth, this ring was the s o u r c e of t h e w a t e r s c a u s i n g t h e b i b l i c a l Flood. During the first three d e c a d e s of t h e t w e n t i e t h c e n tury, the catastrophists were d o m i n a t e d by t h e i d e a s of George McCready Price, a S e v e n t h Day A d v e n t i s t , who w a s b o r n in 1870 in C a n a d a . He r e c e i v e d t h r e e y e a r s of college training plus several y e a r s of r e l i g i o u s e d u c a t i o n . After having held a number of t e a c h i n g p o s t s , h e b e c a m e a p r o f e s s o r of g e o l o g y at a s m a l l A d v e n t i s t c o l l e g e in
Nebraska, U.S.A. He published countless articles and t h r e e b o o k s : Euolutionary Geology and the New Catastrophism, The New Geology, a n d Common Sense Geolo2:y. A m o n g t h e s e b o o k s , the s e c o n d , 726 p a g e s l o n g and p u b l i s h e d in 1923, is t h e m o s t i m p o r t a n t in o r d e r to f a m i l i a r i z e o n e s e l f with h i s v i e w s . His ideas are eenteredaround his biblically-founded belief t h a t t h e e n t i r e c r e a t i o n took p l a c e in s i x l i t e r a l d a y s a few t h o u s a n d y e a r s b e f o r e Christ. The successive laye r s w h i c h c a n be s e e n in the earth's crust are not taken to i n d i c a t e d i f f e r e n t g e o l o g i cal ages. Price stated that t h e s e w e r e all l a i d down s i m u l t a n e o u s l y by t h e G r e a t F l o o d d e s c r i b e d in t h e book "Genesis". Fossils are be-
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ginning independent research. Judging from the quality of these papers, the future of Soviet deep seismic sounding is in good hands. The price of the Consultants Bureau translation(U.S. $22.50) will discourage many young researchers from buying this volume. I hope, however, that every serious student of the earth's crust will have Problems in Deep S e i s m i c Sou~Ming a v a i l a b l e in h i s i n s t i t u t i o n ' s r e f e r e n c e l i b r a r y , on h i s own b o o k s h e l v e s , o r in h i s c o l l e a g u e ' s office down t h e hall. L.C. Pakiser REFERENCES S t e i n h a r t , J.S. a n d M e y e r , R . P . , 1961. E x p l o s i o n s t u d i e s of c o n t i n e n t a l s t r u c t u r e .
Carnegie Inst. Wash. Publ., 6 2 2 : 4 0 9 pp. Pakiser, L.C. and S t e i n h a r t , J . S . , 1964. E x p l o s i o n s e i s m o l o g y in t h e W e s t e r n H e m i s p h e r e . In: H. Odishaw (Editor), Research
in g e o p h y s i c s , 2. Solid Earth and Interface Phenomeua. Mass. Inst. Technol. Press, Cambridge, Mass. pp.123-147. i
Tectonic Model Experiments H. R a m b e r g , 1967. Gravity,
Deformation and the Earth's Crust. A c a d e m i c P r e s s , L o n d o n , 214 pp., 116 f i g . , 9 p l a t e s , 75 a 6 d . T h i s book s h o u l d b e r e g a r d ed a s a m i l e - s t o n e in t e c t o n i c m o d e l e x p e r i m e n t s . It is the first time someone has t a k e n a d v a n t a g e of t h e p o s s i b i l i t y , k n o w n in p r i n c i p l e f o r a l o n g t i m e , of m a k i n g e x p e r i m e n t s in a c e n t r i f u g e m a c h i n e . T h e i n c r e a s e of gravity thus compensates partially for the tremendous m a g n i t u d e of t h e l e n g t h s c a l e , and p e r m i t s t h e u s e of model-building material which has strength enough for c o n v e n i e n t h a n d l i n g and, m o s t i m p o r t a n t of all, e a s y
s t u d y of s h a p e s a f t e r t h e experiment. A c o n s i d e r a b l e a m o u n t of w o r k h a s b e e n s p e n t to b u i l d a centrifuge machine producing a c c e l e r a t i o n s up to 2,900 x g, a n d to s e l e c t a v a r i e t y of m a t e r i a l s with d i f f e r e n t s t r e n g t h s , d e n s i t i e s and colo u r s . A g r e a t n u m b e r of e x periments have been carefully p l a n n e d a n d c a r r i e d out and t h e i r r e s u l t s h a v e b e e n a n a l y s e d and r e c o r d e d by good photographs. It is a pity t h a t c o m p a r a b l e c a r e h a s n o t b e e n t a k e n to make a reliable, correct, mathematical analysis, although such mathematical t r e a t m e n t is f u n d a m e n t a l to a c o r r e c t i n t e r p r e t a t i o n of scale model experiments. The a u t h o r i g n o r e s t h e v e r y fund a m e n t a l s of m e c h a n i c a l a n a lysis, which have been classical for m o r e t h a n a c e n t u r y . The t h e o r y e x p o s e d in t h e f i r s t 40 p a g e s of t h e book, a l t h o u g h c r o w d e d with m a t h e m a t i c a l f o r m u l a s , is nothing more than the formul a t i o n of v a g u e i n t u i t i o n s , a n d is, f r o m a m a t h e m a t i c a l p o i n t of v i e w , q u i t e i n c o n s i s tent. The author uses a " s h a p e p o t e n t i a l " w h i c h is not a potential, ignores the mat h e m a t i c a l d e f i n i t i o n of s t r e s s w h i c h is m i x e d up with v o l u m e f o r c e s (eq.5, p.4), u s e s the t i m e s c a l e of d y n a m i c s (p.38) i n s t e a d of the s t a t i c t i m e s c a l e a l t h o u g h he h a d j u s t s h o w n it w a s not r e l e v a n t . It would be too l e n g t h y to p o i n t out h e r e all the c o r r e c t i o n s t h a t s h o u l d be m a d e to t h e w h o l e o{* the f i r s t five chapters. T h e r e s u l t of t h i s i n e x p l i c a b l e f a i l u r e of the m a t h e m a t i c a l t r e a t m e n t is t h a t the d i s t i n c t i o n b e t w e e n the two q u i t e d i f f e r e n t s o r t s of s i m i l a r i t y of v i s c o s i t y a n d p l a s t i city (the l a t e r with a f i n i t e y i e l d s t r e s s ) is not m a d e . Without e v e n b e i n g a w a r e of it, t h e a u t h o r u s e s the v i s c o s i t y m o d e l . It s e e m s to m e likely t h a t t h e p l a s t i c i t y e q u a t i o n s would be m u c h c l o s e r to t h e a c t u a l p r o p e r t i e s of r o c k s , a s well a s to
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the m a t e r i a l s u s e d in the e x p e r i m e n t s . But the data that would be n e c e s s a r y for an i n t e r p r e t a t i o n following the laws of p l a s t i c i t y a r e lacking. T h u s d e s p i t e the a u t h o r ' s intention, t h e s e e x p e r i m e n t s cannot be taken a s giving quantitative results. Their value is chiefly to appeal to the i m a g i n a t i o n , a n d to s u g g e s t tectonic s h a p e s and p r o c e s s e s . E v e r y geologist i n t e r e s t e d in t e c t o n i c s should e x a m i n e with deep i n t e r e s t the p i c t u r e s of m o d e l s def o r m e d in the c e n t r i f u g e m a c h i n e , and s o m e of t h e s e p i c t u r e s m a y well b e c o m e c l a s s i c a l . But t h i s does not m e a n that all the a u t h o r ' s c o n c l u s i o n s will be accepted. His m a c h i n e allows only the study of g r a v i t a t i o n a l r e a d j u s t m e n t for a l a y e r s e q u e n c e in which density does not a l w a y s i n c r e a s e t o w a r d s the bottom; it does not d i r e c t l y p r o d u c e a l a t e r a l c o m p r e s s i o n . But, it is c l e a r that t h i s is not a r e a s o n to deny that s u c h p r o c e s s e s m a y play a p a r t in actual tectonic d e f o r m a t i o n s . Along t h i s p r i n c i p l e , a n u m b e r of e x p e r i m e n t s have been p e r f o r m e d and although their g e n e r a l s e t t i n g is r a t h e r similar, interpretations are given in which i n c r e a s i n g s c a l e s of d i m e n s i o n a r e a s s u m e d a s m o d e l s for m o r e and m o r e e x t e n s i v e phenom e n a , even though the s p e e d of r o t a t i o n and, thus, the c e n t r i f u g a l f o r c e , is about the s a m e . After a c h a p t e r devoted to e x p e r i m e n t s not u s i n g the centrifuge machine, a first s e q u e n c e of c e n t r i f u g e exper i m e n t s a r e taken a s r e p r e s e n t i n g s a l t p l u g s , or s a l t d o m e s . T h i s is s u r e l y the most easily reproduceable s t r u c t u r e , s i n c e no f o r c e other than g r a v i t y is at work. The d i s c u s s i o n gives i n t e r e s t i n g indications of the d i s t a n c e between n e i g h b o u r ing d o m e s a s r e l a t e d to the t h i c k n e s s of the s a l t l a y e r , of the m a r g i n a l s i n k and of the n a t u r e of s t r a i n of the
s a l t d o m e itself. T h i s is a p o s i t i v e r e t u r n on c e n t r i f u g e e x p e r i m e n t s , but it should be pointed out that s o m e of t h e s e r e s u l t s can be obtained by t h e o r e t i c a l m e c h a n i c a l analysis. Another s e t of e x p e r i m e n t s is d e s i g n e d to study the int r u s i o n of a m o l t e n m a g m a which is l i g h t e r than the s u r r o u n d i n g r o c k s . The m a g m a is r e p r e s e n t e d by an a q u e o u s solution which s t a i n s the path it follows. Such exper i m e n t s can r e p r e s e n t only mechanical effects, however, and one could wonder if t h e r m a l e f f e c t s , s u c h a s vap o r i z a t i o n of w a t e r , do not play an i m p o r t a n t r o l e in actual m a g m a t i c i n t r u s i o n s . Other e x p e r i m e n t s , a l w a y s with d e n s e l a y e r s at the top, differ in the l a t e r a l e x t e n s i o n of t h e s e d e n s e l a y e r s , or s o m e v a r i a t i o n s in the d i s t r i bution of s t r e n g t h . T h e r e is no r e a l d i f f e r e n c e between the s i n k i n g of a heavy l a y e r and the r i s e of a buoyant deep l a y e r . One of the m o s t int e r e s t i n g f e a t u r e s of t h e s e e x p e r i m e n t s is that when t h e r e is a light l a y e r at the top, it m a y be l a t e r a l l y c o m p r e s s e d by the m a t t e r r i s i n g f r o m beneath and o v e r r i d d e n by a m o r e d e n s e l a y e r . Some p i c t u r e s of s e c t i o n s of s u c h models featuring rising d o m e s with lobate s t r u c t u r e s c o m i n g f r o m the depth and s p r e a d i n g over a d e n s e l a y e r , show a r a t h e r s t r i k i n g s i m i l a r i t y to c l a s s i c a l s e c t i o n s of alpine n a p p e s . But it is difficult to a c c e p t a s i m i l a r o r i gin, s i n c e the deep buoyant m a t t e r would not likely be of s e d i m e n t a r y origin, as a r e the alpine n a p p e s . Such e x p e r i m e n t s which d e m o n s t r a t e the r i s e of a deep buoyant l a y e r a r e a l s o taken a s m o d e l s for g r a n i t i c i n t r u s i o n . Since g r a v i m e t r y h a s provided e v i d e n c e for the low d e n s i t y of g r a n i t i c i n t r u s i o n s , I feel the geological i m p l i c a t i o n s of t h i s fact h a v e not yet r e c e i v e d s u f f i cient attention. P r o f e s s o r R a m b e r g ' s ideas about the r o l e played by g r a v i t y buoy-
ancy in g r a n i t i c i n t r u s i o n s , and the r e l a t e d model experiments, deserve serious c o n s i d e r a t i o n . They draw attention to i n t e r e s t i n g c o m p a r i s o n s between field occ u r r e n c e s of acid and b a s i c r o c k s with e x a m p l e s taken from the Scandinavian Caledonides. At a still larger scale, some experiments are taken as models for convection currents in the mantle, it should be pointed out that the author does not make a clearcut distinction between crust and mantle, and this may well be wise. But, these models of deep-seated convection c u r rents clearly produce these lateral compressions in the upper layers which were ruled out by the author when he was studying superficial layers alone (see, for instance fig.t12). Perhaps because an accurate mechanical analysis is lacking, the author takes no account of the outer surface shape, although it must play an important part in any gravitational settling, as can easily be shown for salt domes. In some of the experiments which are assumed to provide models for the largest features, there is, on top of the model, a light l a y e r of " s o f t wax" or "oilwax m i x t u r e " with a v e r y l o w s t r e n g t h . T h e r e is no explanation as to the r o l e this l a y e r is s u p p o s e d to playr In fact, it r e d u c e s the effect of the d e n s i t y of the next l a y e r , in c o m p a r i s o n to the d i f f e r e n c e s of d e n s i t y between d i f f e r e n t l a y e r s . But the anal y s i s of the effect it h a s on the s h a p e of the s u r f a c e is lacking. The a u t h o r h a s put m o r e s t r e s s on v e r t i c a l s e c t i o n s of m o d e l s than on a r e a l d i s tribution of d e f o r m a t i o n s (although the p i c t u r e on the cover of the book shows one of these). In fact, this d i s t r i bution of c o m p r e s s i o n and e x t e n s i o n is too c l o s e l y r e l a t e d to the s e t t i n g of exp e r i m e n t s to give m u c h inf o r m a t i o n , be it of the c i r -
c u l a r e x t e r n a l s h a p e , or t h e s h a p e g i v e n to t h e l a y e r s w h i c h do not e x t e n d to t h e whole model. N e v e r t h e l e s s , I t h i n k t h i s is t h e d i r e c t i o n in w h i c h n e w r e s e a r c h s h o u l d be c a r r i e d on with t h e a u t h o r ' s c e n t r i fuge m a c h i n e . T h i s v e r y efficient device has been u s e d f o r t h e s t u d y of one peculiar tectonic phenomenon, g r a v i t a t i o n a l s u b s i d e n c e . It c a n a l s o be u s e d f o r t h e s t u d y of l a t e r a l c o m p r e s s i o n of s t r a t i f i e d l a y e r s by u s i n g some devices such as the one s h o w n in fig.25 and 26. I am sure such experiments could bring very interesting r e s u l t s , e s p e c i a l l y if an u p to-date mathematical treatm e n t is a p p l i e d . I a m a w a i t ing with d e e p i n t e r e s t a l a t e r book in w h i c h s u c h e x p e r i m e n t s will b e r e c o r d e d . -
J. Goguel
Classic Work on Continental Drift A. W e g e n e r , 1966. The Origin o f Continents and Oceans ( E n g l i s h t r a n s l a t i o n of 4th G e r m a n r e v i s e d e d i t i o n , 1929). D o v e r P u b l i c a t i o n s , New Y o r k , N.Y., 246 pp., 64 fig., U.S.
$~.00. T h e t h e o r y of c o n t i n e n t a l d r i f t h a s f o r m e d a p a r t of g e o l o g i c a l t h o u g h t s i n c e its initial c o n c e p t i o n . F r a n c i s B a c o n (1620), Von H u m b o l d t (1800), Owen (1857), S n i d e r (1858), F i s h e r (1881, 1889), P i e k e r i n g (1907), T a y l o r (1910), B a k e r (1911) a r e s o m e of t h e n a m e s m e n t i o n e d in p r o f e s s i o n a l l i t e r a t u r e in this connection. But it w a s A l f r e d W e g e n e r (1912-1928) who s u c c e e d e d in g a i n i n g w i d e s p r e a d a t t e n tion a n d s u p p o r t f o r t h i s c o n c e p t by b r i n g i n g p a l a e o climatic and other diagnostic f a c t s a s e v i d e n c e to b e a r on it. B e c a u s e of t h e f e e b l e m e c h a n i s m f o r d r i f t to w h i c h Wegener resorted as a mec h a n i c a l e x p l a n a t i o n , how-
ever, there was and still is resistance among many earth- scientists to accepting this concept as a basic principle in the geodynamic evolution of the earth's crust (e.g., Beloussov). In the old controversy between fixism and mobilism (the static and the dynamic models of crustal evolution), a new scientific tool, palaeomagnetism, has recently brought forward independent (diagnostic) facts. Consequently, discussions about d r i f t h a v e f l a r e d up a g a i n .
In t h e s e d i s c u s s i o n s m a n y authors quote Wegener's w o r k Entstehung der Kontinente without h a v i n g b e e n able to rea,~ the G e r m a n text. T h e r e f o r e , he is often m i s represented. T h e i n t i t i a t i v e to m a k e t h i s c l a s s i c e a s i l y a v a i l a b l e to English speaking and reading earth scientists is, therefore, a v e r y w e l c o m e one. T h e t r a n s l a t i o n by J o h n B i r a m is e x c e l l e n t a n d t h e p r i c e of t h i s p a p e r b a c k e d i t i o n is reasonable. R.W. van Bemmelen
Uniformitarianism, Catastrophism and Christian Faith D.W. P a t t e n , 1966. The Biblical Flood and the Ice Epoch. - P a c i f i c M e r i d i a n Publ. Co., S e a t t l e , W a s h . , 336 pp., 27 fig., 13 t a b l e s , U.S. $ 7.50. F r o m t h e m o m e n t t h a t t h e o r i e s of e v o l u t i o n and u n i f o r m i t a r i a n i s m w e r e i n t r o d u c e d to the s c i e n t i f i c w o r l d , t h e r e h a v e b e e n p e o p l e r e j e c t i n g t h e s e v i e w s . S e v e r a l did s o b e c a u s e t h e y felt t h e y h a d to d e f e n d t h e i r C h r i s t i a n faith a g a i n s t t h e p o s t u l a t e s of s c i e n c e . T o t h e s e p e o p l e , t w o m a i n w a y s w e r e o p e n t o f i g h t t h e m a i n s t r e a m of s c i e n t i f i c d e v e l o p m e n t . One a l t e r n a tive w a s s i m p l y to r e j e c t what s c i e n t i s t s s a i d a b o u t e v o l u t i o n and t h e h i s t o r y of t h e e a r t h . T h e o t h e r w a s to p r o d u c e a l t e r n a tive t h e o r i e s of e v o l u t i o n a n d u n i f o r m i t a r i a n i s m . A m o n g t h o s e who a d o p t e d t h e l a t t e r c o u r s e is t h e s m a l l g r o u p of t h e s o c a l l e d c a t a s t r o p h i s t s . M o s t , b u t not all, of t h e s e p e o p l e c a m e f r o m s m a l l and c o n s e r v a t i v e P r o t e s t a n t c i r c l e s . In 1886, I s a a c Newton Vail, a Q u a k e r , p u b l i s h e d a book, The Waters aboz~e the F i r m a ment, in w h i c h h e l a u n c h e d his theory that each planet p a s s e d t h r o u g h a p h a s e in w h i c h it h a d a r i n g s i m i l a r to S a t u r n ' s . In the c a s e of our earth, this ring was the s o u r c e of t h e w a t e r s c a u s i n g t h e b i b l i c a l Flood. During the first three d e c a d e s of t h e t w e n t i e t h c e n tury, the catastrophists were d o m i n a t e d by t h e i d e a s of George McCready Price, a S e v e n t h Day A d v e n t i s t , who w a s b o r n in 1870 in C a n a d a . He r e c e i v e d t h r e e y e a r s of college training plus several y e a r s of r e l i g i o u s e d u c a t i o n . After having held a number of t e a c h i n g p o s t s , h e b e c a m e a p r o f e s s o r of g e o l o g y at a s m a l l A d v e n t i s t c o l l e g e in
Nebraska, U.S.A. He published countless articles and t h r e e b o o k s : Euolutionary Geology and the New Catastrophism, The New Geology, a n d Common Sense Geolo2:y. A m o n g t h e s e b o o k s , the s e c o n d , 726 p a g e s l o n g and p u b l i s h e d in 1923, is t h e m o s t i m p o r t a n t in o r d e r to f a m i l i a r i z e o n e s e l f with h i s v i e w s . His ideas are eenteredaround his biblically-founded belief t h a t t h e e n t i r e c r e a t i o n took p l a c e in s i x l i t e r a l d a y s a few t h o u s a n d y e a r s b e f o r e Christ. The successive laye r s w h i c h c a n be s e e n in the earth's crust are not taken to i n d i c a t e d i f f e r e n t g e o l o g i cal ages. Price stated that t h e s e w e r e all l a i d down s i m u l t a n e o u s l y by t h e G r e a t F l o o d d e s c r i b e d in t h e book "Genesis". Fossils are be-
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