Those Remarkable Floating Rock Formations
by Henry Morris, Ph.D.
The most basic rule of stratigraphy is that sedimentary rock formations on the bottom are older than those on the top. Sedimentary rocks are formed by the erosion, transportation, and deposition of sediments, and nothing could be more obvious than the fact that deposits on top were laid down after the sediments below them. However, this common-sense rule often seems not to work.
"In many places, the oceanic sediments of which mountains are composed are inverted, with the older sediments lying on top of the younger."1
If this is the case, then how did those in authority ever decide that the bottom rocks were younger. The answer is that:
"...fossils have furnished, through their record of the evolution of life on this planet an amazingly effective key to the relative positioning of strata. ..." 2
For true believers in evolution, it may be logical to date rocks this way, even when this requires devising a method for explaining how the sediments got out of order. 3 Since, however, we do not observe evolution taking place today, one must ask how they can be so confident that evolution was true in the past. The answer is that the evolutionary history of life is revealed by the fossil record in the sedimentary rocks. Dr. Pierre P. Grasse´, who for 30 years held the Chair of Evolution at the Sorbonne in Paris, has noted this fact:
"Naturalists must remember that the process of evolution is revealed only through fossil forms." 4
That is, ancient rocks contain fossils of organisms in an early stage of evolution; younger rocks contain fossils representing a more advanced stage of evolution. We know, of course, which rocks are ancient because they are the ones on the bottom, with the younger ones on top. But, then, we have just noted there are many places where this order is reversed. We know they are reversed because of the evolutionary stage of their respective fossils.
Now, if one senses a feeling of dizziness at this point, it is because we are going in circles. Maybe it will help settle our queasiness if we find some actual physical evidence that these gigantic old rock blocks have really ridden up and over the younger ones. We would expect to find, if this is the case, a tremendous amount of rock breakage (brecciation) and ground-up rock powder at the interface, along with deep grooves and scratches (striations) along the under surface, and a general mixture of the upper and lower rocks along the thrust plane. Is this what is found?
Not usually. Usually the contact surface is sharp and well defined, with the older rocks on top of the younger, often with many "ages" missing in between.
"The following observations about 'overthrusts' seem to have universal validity: 1. The contact is usually sharp and unimpressive in view of the great amount of displacement ... 5. Minor folding and faulting can usually be observed in both the thrust plate and the underlying rocks. The intensity of such deformations is normally comparatively weak, at least in view of the large displacements these thrust plates have undergone." 5
It is true, of course, that some "overthrusts" do exhibit evidence of brecciation and other such indicators of relative movement. Does this not prove they are really overthrusts?
Not at all--at least not necessarily. Many types of movement may occur besides overthrusting.
"Late deformations, particularly by normal faulting, are present in many thrust plates. They should be recognized for what they are: post-thrusting features completely unrelated to the emplacement of the thrust plates." 6
Then what deformations can be identified with confidence as caused by the thrust itself? The author of the above says that "basal tongues" from the lower plate are often injected into the base of the overthrust plate, and that these sometimes coalesce. Also secondary "splay" thrusts may be found.
But now suppose that all these physical phenomena--brecciation, rock powder, striations, basal tongues, splay thrusts, etc., that a real overthrust would produce, are actually present, does this finally prove that the rocks have really been moved out of their original depositional order?
Of course not. Such phenomena merely prove that the upper block has moved somewhat with respect to the lower block. This is quite common, even with formations in the "correct" sedimentary order, due to the different physical properties and times of deposition of the two formations, and proves nothing whatever about overthrusting.
Admittedly, such phenomena do not rule out the possibility of overthrusting, as their absence might do. They are necessary, but not sufficient, conditions for overthrusting. More evidence is needed--notably, evidence of the "roots" from which the alleged thrust block was derived, along with evidence that its incredible journey was physically possible.
Are the sources of the overthrust plates usually discernible? Only rarely, and with much speculation. Furthermore, in most cases, there are not any genuine evidences of overthrusting at all.
"Different lithological units, usually with stratigraphic separation measured in kilometers, are in juxtaposition along a sharp contact, often no more impressive than a bedding plane." 7
Why then could it not be a simple bedding plane? And how do geologists explain the tremendous forces and motions in the earth that can accomplish the remarkable feat of moving a gigantic mass of rock great distances up and over another great rock formation? Tremendous compressive forces and rock strengths must be generated, and tremendous frictional forces overcome, before such an operation could ever be accomplished. The mechanism of the phenomenon has always been mysterious, and some of the most competent geophysicists have said it was impossible.
In 1959, however, William Rubey and M. King Hubbert, felt they had solved the problem8, proposing that water trapped in the pores of the sediments as they were deposited gradually became so compressed with the accumulating overburden that they developed "geostatic" pressures, capable actually of floating the formation above into another location.
This suggestion was enthusiastically accepted by most geologists and, for more than two decades, has been by far the most widely adopted solution to the overthrusting problem. However, creationists immediately pointed out serious difficulties with it9 , and these are now becoming generally recognized and admitted.
It is obvious, for example, that these very high pore pressures can be maintained only if (1) the pores in the rock section near the interface are interconnected, so the pressure will be applied over the entire base of the floating slab; (2) the permeability of the cap rock is so low that it provides an effective seal against the water escaping under the high pressure gradient to which it is subjected.
This is a highly unlikely combination of circumstances, and some geologists realize this.
"At high enough pressures and temperatures, plastic flow will certainly reduce pore space inter-connectivity. To be effective mechanically, pore fluids must be inter-connected pore space; it is not clear that this is always the case during metamorphism.... Our preliminary results suggest that the effective permeability of the upper plate must be on the order of 10-3 mD or less for gravity gliding to be feasible. Otherwise, the fluid will leak away from the zone of decollement before pore pressure can reach the levels needed for gravity gliding. Although in situ rock permeabilities are poorly known, the few existing measurements suggest that effective permeabilities as low as 10-3 mD are rare in the geologic column... 10
But suppose that, in some cases, rocks such as shales and evaporates do have sufficiently low permeabilities to seal off the high pressure zone. Now the problem becomes one of rock strength--the pressures become so high as to fracture the rocks!
" ... when the pore fluid pressure exceeds the least compressive stress, fractures will form normal to that stress direction--we suggest that pore pressure may never get high enough to allow gravity gliding as envisaged by Hubbert and Rubey..." 11
If fractures develop, of course, this increases the permeability and the water flows out, lowering the pressure and stalling any incipient flotation. Furthermore, it is simply inconceivable that these huge (often many miles long, wide and thick) slabs of rock could traverse the long distances necessary without fractures developing from other causes as well. There seems no way to avoid escape of pore water through at least some fractures. By Pascal's law, if the pressure is lowered at any point in a continuous water body, it must drop by the same amount throughout the entire body. The whole scenario seems impossible, hydraulically,
"We suspect that over the areas of large thrust sheets such as those in the Appalachians or the Western Cordillera, effective permeabilities would have been too large to allow gravity gliding even with shale or evaporate cap rocks." 12
It thus begins to appear that overthrusting by floating is impossible on any noteworthy scale. But this is not quite the last resort of those who must salvage the evolutionary order at all costs.
"Simple gravity gliding under the influence of elevated pore pressure cannot explain the Heart Mountain fault... Pierce has suggested a catastrophic genesis for the Heart Mountain allochthon." 13
William Pierce has been studying the Heart Mountain "overthrust" (Paleozoic over Eocene) for many years. Originally, he thought it was caused by simple gravity sliding, but this proved impossible mechanically. Then it was suggested that the mechanism might have involved the Hubbert and Rubey fluid-pressure concept. Now that he finds that won't work either, he has invoked catastrophism--and catastrophism with a vengeance, postulating an explosive transplantation of the thrust blocks! 14 Catastrophic events, however, obviously can neither be observed in process nor modeled in the laboratory.
"Catastrophic processes are beyond the scope of this analysis." 15
One can believe in catastrophic overthrusting if his motivation to do so is sufficiently strong, of course. If evolutionists want to retain their cherished evolutionary sequences, therefore, they can do so only by faith in catastrophism. Floating rock formations won't float!
1. B.P. Ryan, "Mountain-building in the Mediterranean," Science News, V. 98, Oct. 17, 1970, p. 316.
2. H.D. Hedberg, "The Stratigraphic Panorama." Bulletin of the Geological Society of America, V. 72, Apr. 1961, p. 499.
3. In a few cases, and on a small scale, the strata can actually be traced in such a way as to show that the rocks have been physically displaced from their original depositional sequences by folding or faulting, but this is not the usual situation.
4. Pierre P. Grasse´. Evolution of Living Organisms (New York, Academic Press, 1977), p. 4.
5. P.E. Gretener, "On the Character of Thrust Faults with Particular Reference to the Basal Tongues," Bulletin of Canadian Petroleum Geology, V. 25, 1977, p. 110.
7. P.E. Gretener, op. cit., p. 111.
8. M. King Hubbert and Wm. W. Rubey, "Role of Fluid Pressure in Mechanics of Overthrust Faulting," Bulletin of Geological Society of America, V. 70, Feb. 1979, pp. 155-166.
9. John Whitcomb and Henry M. Morris, The Genesis Flood (Philadelphia, Presbyterian and Reformed, 1961) pp. 196-200.
10. J.H. Willemin, P.L. Guth and K.V. Hodges. "Comment and Reply on 'High Fluid Pressure, Isothermal Surfaces, and the Initiation of Nappe Movement' " Geology, V. 8, Sep. 1980, p. 405.
11. Ibid., p. 406.
12. Peter L. Guth, L.V. Hodges and J.H. Willemin, "Limitations on the Role of Pore Pressure in Gravity Sliding" Geological Society of America Bulletin. V. 93, Jul. 1982, p. 61 1.
14. William G. Pierce, Clastic Dykes of Heart Mountain Fault Breccia, Northwestern Wyoming, and their Significance (Washington, U.S. Geological Survey Professional Paper 1133, 1979) 25 pp.
15. Guth, Hodges, and Willemin, op. cit., p. 611.
*Dr. Henry M. Morris is Founder and President Emeritus of the Institute for Creation Research.