Selections from Origin of Appalachian Geomorphology, Part II: Formation of Surficial Erosion Surfaces, by Michael J. Oard.
(These selections by Marko Malyj are of the article published in Creation Research Society Quarterly Journal, Volume 42, Number 2, Fall 2011)
An erosion surface is a land surface shaped and subdued by the action of erosion, especially by running water. A nearly flat erosion surface is called a planation surface. Gravel-capped planation surfaces are found all over the Earth. Good examples are found in the northern High Plains of western North America. Figure 2 shows the flat surface of the highest planation surface, the Cypress Hills of southeast Alberta and southwest Saskatchewan, Canada (Oard and Klevberg, 1998).
(To receive new uMarko posts via a daily email, please click Subscribe)
(On Twitter: FOLLOW uMarko or http://www.twitter.com/uMarko)
|Cypress HIlls planation surface near Reser Lake, Canada, Elevation 1300 meters.|
In the 1800s, many geologists believed that erosion and planation surfaces were caused by marine planation during sea level rises. Then in about 1900, William Morris Davis developed the “cycle of erosion” or the “geographical cycle” for the formation of erosion surfaces called peneplains.
The Rise and Fall of Davis’s “Cycle of Erosion”
Davis imagined that the many erosion and planation surfaces there were caused by ancient rivers and streams sweeping back and forth, smoothing the land over millions of years. Davis’ idea was strongly influenced by the theory of evolution (Flemal, 1971).
Davis believed that, just like life, landscapes evolved through progressive stages, each exhibiting characteristic landforms. Davis applied the popular analogy of age to landscapes. They initially started in their youth, with the tectonic uplift of a level surface; progressed to maturity, with strong dissection by rivers and streams; and finally reached old age, where the land is finally subdued to a low relief peneplain near sea level (Johnson, 1954) and ready for another cycle.
But this idea is fraught with difficulties. During the early 1900s, despite its popularity, geologists slowly became skeptical. By the 1950s, the hypothesis was widely rejected.
Davis could not demonstrate the transitions between stages by detailed observations and experimentation. When challenged on that point, he simply pointed out the many flat surfaces of Earth’s landscape as evidence for his hypothesis (Johnson, 1954; Chorley et al., 1973, pp. 242, 243)—a logical fallacy called begging the question, a type of circular reasoning.
Peneplains are rolling erosion surfaces. To form a flat planation surface would take more time than was available, even on the geologic timescale. Ollier (1991, p. 200) claimed that just one-half of Davis’s cycle took the last half of the Phanerozoic, or 250 million years, in the highlands of southeast Australia!
Another major problem is that streams and rivers dissect a surface; they do not plane it. Davis also failed to provide any examples of the ending stage: a peneplain at sea level (Flemal, 1971; Chorley et al., 1973, Phillips, 2002).
The Weathering Hypothesis
A number of other hypotheses have been proposed in place of the cycle of erosion, but none seem to have fared well. These hypotheses include Walther Penck’s erosion during slow tectonics, Lester King’s parallel retreat of slopes, John Hack’s dynamic equilibrium, C. H. Crickmay’s lateral planation and unequal erosion, and the weathering hypothesis developed in the early to mid-1900s. The weathering hypothesis is the most popular idea today and seems to have survived among geomorphologists.
In the weathering hypothesis, erosion or planation surfaces form by two processes. First, a landscape is chemically weathered downward with time. The boundary between the weathered debris and unweathered rock is called the weathering front. Most weathering is accomplished by ubiquitous shallow
groundwater (Baker and Twidale, 1991, p. 81). Second, the weathered debris is removed by sheet wash, stream erosion, or other mechanisms.
However, there are many problems with the weathering hypothesis.
1) Weathering causes a rough surface, not a planation surface. Most telling, weathering does not form a planation surface and would form an erosion surface only with great difficulty. Factors driving weathering rate vary spatially (Birkland, 1984; Hall, 1988), as does erosion. Lithology and drainage patterns are especially relevant to the weathering rate (Summerfield, 1991). Therefore, the weathering front should
be rough and not planar. Twidale (2004, p. 160) stated: “Weaknesses
in the country rock are exploited by moisture and the weathering front is frequently irregular in detail: a topography is developed.” How could an exceptionally flat surface over a large area form by such irregular weathering?
2) weathering is more likely to destroy a planation surface than to create on Hall (1988, p.12)
3) Weathered debris must be stripped from the area. Even if the weathering occurred on a planar surface, there is the problem of stripping the debris away just as evenly (Bishop, 1966). King (1975, p. 309) questioned how deep weathering products could be removed from a flat surface, leaving no weathered material behind.
4) planation surfaces sometimes cut across both weathered and unweathered surfaces, indicating that planation is independent of weathering (Bishop, 1966, p. 149).
5) How would the weathering hypothesis account for all the rounded rocks on top of some planation and erosion surfaces, especially those obviously transported long distances? The weathering hypothesis cannot account for any of these, whether on the high plains of Montana or the rolling plains and plateaus of Kentucky.
Evolutionary Uniformitarian Hypotheses do explain Flat Plains
Davis confidently predicted that uniformitarianism would lead to robust explanations of landforms during the twentieth century, but it seems he was as wrong about that as he was about the cycle of erosion. Why have scientists failed to explain such common, obvious features? Once confident in their explanations, geomorphologists now wander in the wilderness (Baker and Twidale, 1991, p. 81). Could it be that their basic starting premise of uniformitarianism, or actualism, is wrong and needs to be discarded?
Ahnert (1998, p. 229) noted that new approaches with new methods are required to understand erosion surfaces (his peneplains): “There are still many aspects of peneplains to be explained. Perhaps some entirely new approaches with new methods are needed.”
I agree that a new approach is needed—a catastrophic approach.
Erosion Surfaces were Created by Runoff from the Genesis Flood
Davis’s antipathy to the Genesis Flood led geomorphology into a dead end. That is because the key to geomorphology is the Genesis Flood (Oard, 2008), precisely contrary to conventional thinking over the past century.
It is looking like planation and erosion surfaces can be explained by—and only by—the retreat of Floodwaters off emerging continents. Since many planation surfaces are quite large, covering areas > 2,500 km2, planation requires a large-scale process, best explained by the sheet-flow phase of Walker’s (1994) model (Figure 38).
|Figure 38. Walker’s classification of the Flood into the 150-day flooding stage and the 221-day retreating stage with five phases. Large scale erosion surfaces were created by water runoff during the retreating sheet flow stage.|
Proponents of the weathering hypothesis can take comfort in one thing: no other secular geomorphological hypothesis explains the observations either. They all have numerous weaknesses, as noted by conventional old-age geologists (Crickmay 1974, p. 192, brackets mine):
The difficulty that now confronts the student [all who study geomorphology] is that, though there are plenty of hypotheses of geomorphic evolution, there is not one that would not be rejected by any majority vote for all competent minds. This situation is in itself remarkable in a respectable department of science in the latter half of the 20th Century.
This situation is remarkable indeed! The only scientific explanation must be a catastrophic approach. Planation and erosion surfaces that are common worldwide must have formed in the past by some large-scale unique event (Oard, 2008).
Large erosion surfaces would have easily formed during the sheet-flow phase of the retreating stage of the Genesis Flood. Like many similar locations worldwide, water flowing away from the rising Appalachian Mountains planed the land, creating erosion surfaces on both sides of the mountains. The speed of the erosional event, the extent of the sheet-flow currents, and the water velocity are all recorded in the presence of large erosion surfaces with erosional remnants and resistant gravels transported over great distances.
Baker, V.R., and C.R. Twidale. 1991. The reenchantment of geomorphology.Geomorphology 4:73–100.
Birkeland, P.W. 1984. Soils and Geomorphology. Oxford University Press, New York, NY.
Bishop, W.W. 1966. Stratigraphical geomorphology: a review of some East African landforms. In Dury, B.H. (editor), Essays in Geomorphology, pp. 139–176. Heinemann, London, UK.
Chorley, R.J., R.P. Beckinsale, and A.J. Dunn. 1973. The History of the Study of Landforms or the Development of Geomorphology—Volume Two: The Life and Work of William Morris Davis. Methuen & Co. LTD, London. UK.
Crickmay, C.H. 1974. The Work of the River: A Critical Study of the Central Aspects of Geomorphology. American Elsevier Publishing Co., New York, NY.
Flemal, R.C. 1971. The attack on the Davisian system of geomorphology: a synopsis. Journal of Geological Education 19:3–13.
Hall, K.J. 1988. Weathering. In Moon B.P., and G.F. Dardis (editors), The Geomorphology of Southern Africa, pp. 12–29. Johannesburg, South Africa.
King, L. 1975. Bornhardt landforms and what they teach. Zeitschrift für Geomorpholgie N. F. 19:299–318.
Oard, M.J., and P. Klevberg. 1998. A diluvial interpretation of the Cypress Hills Formation, Flaxville gravels, and related deposits. In Walsh, R.E. (editor), Proceedings of the Fourth International Conference on Creationism, technical symposium sessions, pp.421–436. Creation Science Fellowship, Pittsburgh, PA.
Oard, M.J. 2008. Flood by Design: Receding Water Shapes the Earth’s
Surface. Master Books, Green Forest, AR.
Summerfield, M.A. 1991. Global Geomorphology. Longman Scientific & Technical, New York, NY.
Twidale, C.R. 2004. River patterns and their meaning. Earth-Science Reviews 67:159–218.
Walker, T. 1994. A Biblical geological model. In Walsh, R.E. (editor), Proceedings of the Third International Conference on Creationism, technical symposium sessions, pp. 581–592. Creation Science
Fellowship, Pittsburgh, PA.