Twenty years ago geologists were certain that the data correlated perfectly with the then-reigning model of stationary continents. The handful of geologists who promoted the notion of continental drift were accused of indulging in pseudoscientific fancy. Today, the opinion is reversed. The theory of moving continents is now the ruling paradigm and those who question it are often referred to as stubborn or ignorant. This "revolution" in our concept of the earth's character is a striking commentary on the human nature of scientists and on the flexibility that scientists allow in use of the geological data.
Plate Tectonics
The popular theory of drifting continents and oceans is called "plate tectonics."1 (Tectonics is the field of geology which studies the processes which deform the earth’s crust.) The general tenets of the popular theory may be stated as follows. The outer lithospheric shell of the earth consists of a mosaic of rigid plates, each in motion relative to adjacent plates. Deformation occurs at the margins of plates by three basic types of motion: horizontal extension, horizontal slipping, and horizontal compression. Sea-floor spreading occurs where two plates are diverging horizontally (e.g., the Mid-Atlantic Ridge and East Pacific Rise) with new material from the earth's mantle being added between them to form a new oceanic crust. Transform faulting occurs where one plate is slipping horizontally past another (e.g., the San Andreas fault of California and the Anatolian fault of northern Turkey). Subduction occurs where two plates are converging with one plate underthrusting the other producing what is supposed to be compressional deformation (e.g., the Peru-Chile Trench and associated Andes Mountains of South America). In conformity with evolutionary-uniformitarian assumption, popular plate tectonic theory supposes that plates move very slowly — about 2 to 18 centimeters per year. At this rate it would take 100 million years to form an ocean basin or mountain range.
Fitting of Continents
The idea that the continents can be fitted together like a jigsaw puzzle to form a single super continent is an old one. Especially interesting is how the eastern "bulge" of South America can fit into the southwestern "concavity" of Africa. Recent investigators have used computers to fit the continents. The "Bullard fit"2 gives one of the best reconstructions of how Africa, South America, Europe, and North America may have once touched. There are, however, areas of overlap of continents and one large area which must be omitted from consideration (Central America). There are a number of ways to fit Africa, India, Australia, and Antarctica (only one can be correct!). Reconstructions have been shown to be geometrically feasible which are preposterous to continental drift (e.g., rotation of eastern Australia fits nicely into eastern North America).3
Those who appreciate the overall fit of continents call the evidence "compelling," while others who note gaps, overlaps, or emissions remain skeptical. It is difficult to place probability on the accuracy of reconstructions and one's final judgment is largely subjective.
Sea-Floor Spreading
Evidence suggesting sea-floor spreading is claimed by many geologists to be the most compelling argument for plate tectonics. In the ocean basins along mid-ocean ridges or rises (and in some shallow seas) plates are thought to be diverging slowly and continuously at a rate of several centimeters yearly. Molten material from the earth's mantle is injected continuously between the plates and cools to form new crust. The youngest crust is claimed to be at the crest of the ocean rise or ridge with older crust farther from the crest. At the time of cooling, the rock acquires magnetism from the earth's magnetic field. Since the magnetic field of earth is supposed by many geologists to have reversed numerous times, during some epochs cooling oceanic crust should be reversely magnetized. If sea-floor spreading is continuous, the ocean floor should possess a magnetic "tape recording" of reversals. A "zebra stripe" pattern of linear magnetic anomalies parallel to the ocean ridge crest has been noted in some areas and potassium-argon dating has been alleged to show older rocks farther from the ridge crest.
There are some major problems with this classic and "most persuasive" evidence of sea-floor spreading. First the magnetic bands may not form by reversals of the earth's magnetic field. Asymmetry of magnetic stripes, not symmetry, is the normal occurrence.4 It has been argued that the linear patterns can be caused by several complex interacting factors (differences in magnetic susceptibility, magnetic reversals, oriented tectonic stresses).5
Second, it is doubtful that the magnetic anomalies have been successfully dated. Wesson6 says that potassium-argon dating when correctly interpreted shows no evidence of increasing age with distance from the ridge system. The greater argon content (giving older apparent age) of ocean basalt on the flanks of the ocean ridges can be explained easily by the greater depth and pressure at the time of solidification incorporating original magmatic argon.7
Subduction
Corollary to the idea of plate accretion by sea-floor spreading is the notion of plate destruction by subduction. (If sea-floor spreading occurs without plate destruction, the quantity of crust will increase and the volume of the earth must increase!). Subduction theory supposes that converging plates are destroyed below ocean trenches. The island arc or coastal mountain range associated with ocean trench subduction zones is claimed to form by compression as one plate is underthrusting another. The plate that is "subducted" below the trench is thought to be remelted at a depth of up to 700 kilometers. Gravity data indicate low density material of crustal character on the landward side below trenches. (Also, deep and high intensity earthquakes (i.e., earthquakes in Alaska, Peru, Nicaragua, etc.) are assumed to indicate break-up of the underthrust plate.
Two major difficulties are encountered by models supposing subduction to explain the modern tectonic phenomena in ocean trenches. First, if subduction theory is correct, there should be compressed, deformed, and thrust faulted sediment on the floors of trenches. Studies of the Peru-Chile Trench and the eastern Aleutian Trench,8 however, show soft flat lying sediment without compression structures. Second, seismic first-motion data indicate that modern earthquakes occurring approximately under trenches and island arcs are often tensional, but only rarely compressional.9
The Mysterious Cause of Drift
What is the driving force for continental drift and plate tectonics? How is a plate ten thousand kilometers long, several thousand kilometers wide, and one hundred kilometers thick, kept in constant but almost imperceptibly slow movement during millions of years? Will slow and continuous application of stress on a plate 100 kilometers thick cause it to be torn asunder? How can a plate be broken and then rammed slowly into the earth's mantle to a depth of 700 kilometers? Here are some of the most baffling problems for plate tectonics.
Evolutionary-uniformitarian explanations for plate motion range from very doubtful to impossible. A popular idea is that rising convection currents in the earth's mantle exert lateral forces on plates moving them slowly and continuously. The best theory of the viscosity of the earth's mantle, however, shows that large-scale convection systems are impossible.10 Three other theories are sometimes mentioned: (1) plates slide by gravity from the elevated mid-ocean ridge to the depressed trench, (2) plates are "pulled" into the mantle below trenches by chemical phase changes during melting, (3) plates are "pushed" apart along mid-ocean ridges by slow injection of magma into vertical cracks. Each of these mechanisms (alone or together) cannot overcome the viscous drag at the base of the plate, and cannot explain how the difference in elevation developed or how the plate boundary originally formed. The absence of sufficient mechanism for plate motion, the uncertainty regarding the existence of sea-floor spreading, and the doubts about subduction cause us to question the popular geologic syntheses known as "plate tectonics."
Continental Drift and the Bible
The Bible framework for earth history makes no statement about continental splitting, so it is unnecessary and unwise to take a "Biblical" position on the question. When God created the land and sea, the waters were "gathered together unto one place" (Genesis 1:9), which may imply one large ocean and one large land mass. The scripture which says "the earth was divided" in the days of Peleg (Genesis 10:25) is generally thought to refer to the Tower of Babel division (Genesis 11:1-9) and some suppose this included continental separation. To believe, however, that the continents moved thousands of miles during the Tower of Babel incident without causing another global flood requires a miracle. Similarly, it is doubtful whether the long day of Joshua can be explained naturalistically by plate tectonics.
If continental separation did occur, the only place within the Bible framework where it could fit would be during Noah's Flood. The cause of Noah's Flood is described in tectonic terms: "all the fountains of the great deep broken up" (Genesis 7:11). The Hebrew word for "broken up" is baga and is used in other Old Testament passages (Zechariah 14:4; Numbers 16:31) to refer to the geologic phenomena of faulting. The mechanism for retreat of the Flood waters is also associated with tectonics. Psalm 104:6,7 describes the abating of the waters which stood above the mountains; the eighth verse properly translated says, "The mountains rose up; the valleys sank down." It is interesting to note that the "mountains of Ararat" (Genesis 8:4), the resting place of the Ark after the 150th day of the Flood, are in a tectonically active region at the junction of three lithospheric plates.11
If continental separation occurred during Noah's Flood, a host of problems in the tectonic dilemma can be solved. Rapid mid-ocean rifting can explain the large quantity of volcanic rocks on the sea floor. The presence of low density crustal rock down to a depth of 700 kilometers within the mantle below trenches can be attributed to rapid underthrusting. The cause for the ancient breaking up of continents can be explained easily by the enormous catastrophic forces of Noah's Flood which broke the lithosphere into moving plates which for a short time overcame the viscous drag of the earth's mantle. The amazing similarity of sedimentary Flood layers in the northeastern United States to those of Britain (i.e., Carboniferous coal strata and Devonian red sandstones) and the absence of these in the North Atlantic ocean basin suggests that continental separation occurred toward the end of the Flood.
Conclusion
The idea that sea-floor plates form slowly and continuously at a rate of a few centimeters each year as the ocean crust is being rift apart, is not supported by geologic data. The concept of destruction of sea-floor plates over millions of years by slow underthrusting below ocean trenches is also doubtful. Furthermore, the cause for the alleged gradual and uninterrupted motion of plates is an unsolved mystery. Despite these failures in the modern theory of "plate tectonics," the notion that the earth's surface has been deformed at the margins of moving plate-like slabs appears to be a valid one. The facts indicate that the separation of the continents, rifting of the ocean floor, and underthrusting of ocean trenches, were accomplished by rapid processes, not occurring today, initiated by a catastrophic mechanism. Noah's Flood, as described in the Bible, was certainly associated with tectonic processes and provides the time in the Biblical framework of earth history when continental separation may have occurred.
REFERENCES
1 For summaries of the literature see J.F. Dewey, Plate tectonics, Sci. Amer., v. 226, 1972, p. 56-68 and W. Sullivan, Continents in motion, the new earth debate: New York, McGraw- Hill, 1974, 399 p. For collections of important, somewhat technical papers affirming plate tectonics, see: Continents adrift, readings from Scientific American: San Francisco, W. H. Freeman & Co., 1973, 172 p. and Allan Cox, ed., Plate tectonics and geomagnetic reversals: San Francisco, W. H. Freeman and Co., 1973, 702 p. For a technical critique of plate tectonics see C. F. Kahle, ed., Plate tectonics - assessments and reassessments: Tulsa, Amer. Assoc. Pet. Geol., Memoir 23, 1974, 514 p.
2 E. C. Bullard, J. E. Everett and A. G. Smith, Fit continents around Atlantic, in P.M.S. Blackett et al., eds., A symposium on continental drift: Roy. Soc. London, Phil. Trans., ser. A, V. 258, 1965, p. 41-75.
3 A. H. Voisey, Some comments on the hypothesis of continental drift, in Continental drift, a symposium: Hobart, Univ. Tasmania, l958, p. 162-171.
4 A. A. Meyerhoff and H. A. Meyerhoff, "The new global tectonics": age of linear magnetic anomalies of ocean basis: American Assoc. Pet. Geol. Bulletin, v 56, 1972, p 337-359.
5 Ibid., p. 354-355.
6 P. S. Wesson, Objections to continental drift and plate tectonics: J. Geol., v. 80, 1972, p. 191.
7 C. S. Noble and J. J. Naughton, Deep-ocean basalts: inert gas content and uncertainties in age dating: Science, v. 162, 1968, p. 265-267. G. B. Dalrymple and J. G. Moore, Argon-40: excess in submarine pillow basalts from Kilauea Volcano, Hawaii: Science, v. 161, 1968, p. 1132-1135.
8 D. W. Scholl, et al., Peru-Chile Trench sediments and sea-floor spreading: Geol. Soc. Amer. Bull., v. 81, 1970, p. 1339-1360. R. E. Van Huene, Structure of the continental margin and tectonism at the eastern Aleutian Trench: Geol. Soc. Amer. Bull., v. 83, 1972, p. 3613-3626.
9 W. F. Tanner, Deep-sea trenches and the compression assumption: Amer. Assoc. Pet. Geol. Bull., v. 57, 1973, p. 2195-2206.
10 For a review of arguments against convection currents see P. S. Wesson, loc. cit., p. 187.
11 J. F. Dewey, et al., Plate tectonics and the evolution of the alpine system: Geol. Soc. Amer. Bull., v. 84, 1973, p. 3139.
