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Rethinking the consensus on coral reef talus


Whether you are a diver, a geologist, or simply someone with an interest in natural history, you are likely to have a misconception about the structure of coral reefs. The error is ubiquitous in textbooks and is reinforced by media treatments of the topic. Everyone ‘knows’ that coral reefs have a central zone of organically bound material (the reef core), a leeward zone of flat lying sediments (the back-reef lagoonal area) and a seaward zone of steeply-dipping rubble (the reef talus). The misconception relates to the reef talus. The source of the erroneous view can be traced to Charles Darwin, who sought to follow his mentor (Charles Lyell) in explaining the past by reference to present-day processes.

“Darwin and his many followers regarded contemporary reefs as having shelf-like forms, with steep slopes facing deep water. This morphology differentiates the familiar zones of backreef, reef-crest and fore-reef. Most accounts emphasize the importance of the reef-crest, comprising the growth framework responsible for generating the reef structure. Material eroded from both the reef-crest and the upper reef-slope has been assumed to accumulate on the fore-reef, and it was argued that this provided the foundations that enabled construction to take place in waters that were otherwise too deep. This pervasive idea can be traced to Darwin (1842) and Dana (1853), although it typically only applies to windward, moderately high hydrodynamic energy, regimes. However, numerous conceptual models illustrate reefs in which the fore-reef is shown as a steep debris slope, on which depositional increments are correlated with contemporary intervals of reef growth.” (from the Introduction).

Why is this worthy of our attention? The principles in evidence here are relevant to a large number of topics that relate to the past. Unfortunately, these origins issues often are characterised by excessive appeals to consensus and cherished models, and not enough attention is given to the weight of evidence. Lyell’s and Darwin’s uniformitarianism still have an undue influence on our educational system and the media. Attempts to increase the level of critical scrutiny are met with emotive responses rather than reasoned arguments. To help us think through our methodology for dealing with these tensions, Braithwaite’s approach to the “reef talus” model may provide a useful case study.

For the full text of this blog, go here.

bornagain77 @ 1: Yes, Steve Austin's comments on the Santa Cruz River locality illustrate the same point. Steve says that Darwin brought a methodology for interpreting the rocks that led him and others astray. In both cases, Darwin used the principle of uniformitarianism selectively. Re coral reefs, storm rubble from the reef is swept inland by storms, so the talus slope must have another mechanism of formation. Similarly, the sheer size of the boulder deposits means that flows must have been different in the past - the present river carries pebbles, sand and mud. The response we should promote is better science. Jaceli123 @ 2: Your question might be better expressed: how can the philosophy of materialism be evaluated? and how can "evolution" be assessed as an explanation of origins? Also, put questions that are more positive: How can the patterns we see in the rock record be explained? How do we understand evidences of variation and adaptation in the broader context of developing a science of origins? For answers - stick around and grapple with the many issues that are being discussed. David Tyler
Hey bornagain77 I'm new to the forum and am a high school student learning the darwinian theory and biology. Which I disagree with. How can materialism and-evolution be shown to be false. Jaceli123
Dr. Tyler, as to this statement:
Darwin illustrates the former - although he claimed to be saying that the present is the key to the past, he invoked only gradualist processes that he thought were operative in the present and failed to test his hypotheses rigorously.
The following video is very interesting for it shows a geological formation that is now known to have been formed by a catastrophic flood, yet Charles Darwin himself had 'predicted' the geological formation was formed 'gradually':
Where Darwin Went Wrong - geology video http://www.youtube.com/watch?v=3darzVqzV2o
Angels We Have Heard on High -ThePianoGuys - video https://www.youtube.com/watch?v=n543eKIdbUI

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