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Coral Reef Formation

16 May 2013

This story is at http://phys.org/print287650630.html … and concerns various theories of how coral reef islands have formed over evolutionary time. A paper in the journal Geology (see also http://geology.gsapubs.org/content/early/2013/05/09/G34109.1.full.pdf+htaml and web.mit.edu/newsoffice/ for MIT News). Darwin suggested fringe reefs, barrier reefs and atolls, all slightly different from each other, form in stages as islands that sink into the ocean floor – the fate of all volcanic islands it was thought. When the sinking begins the coral reefs grow upwards towards the sea surface and a measure of sunlight, disliking the darkness of the ocean depths. They get a modicum of sunlight just below the surface and this is the ideal medium – which is why the scary CAGW story is so potent. Rising seas will drown the coral reefs and kill them. Dead ducking woes. However, some Pacific islands seem to contradict the Darwin explanation, for various reasons (described in the paper) which led the authors to look at a rival explanation, by one Reginald Daly. Reggie argued the sea level changes, not island subsidence, was the key to understanding coral formations. Sea levels are known to have differed in the early Holocene, and most notably during the Ice Ages. Some volcanic islands were flooded as a result of rising seas. However, when sujch islands were above sea level they were subject to erosion by wave energy and all the forces of geological uniformitarianism (or those forces they can summon as frost and ice are out of the question in the tropical zone). When sea levels changed and swamped islands that were otherwise sticking out of the oceans corals grew on the submerged island platforms.

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