Enewetak Atoll

node · earth

An atoll in the northern Marshall Islands, and the place where Darwin's theory of reef formation stopped being a hypothesis. Darwin had argued in 1842 that a fringing reef around a volcanic island becomes a barrier reef and then an atoll as the island subsides, the coral growing upward at roughly the rate the foundation sinks; the alternative, argued through the nineteenth and early twentieth centuries, was that atolls sat on shallow platforms produced by sea-level change and needed no subsidence. The test was a drill hole. In 1952 boreholes on Enewetak, drilled as part of the United States nuclear testing programme's site investigation, passed through more than a kilometre of reef-derived carbonate before reaching volcanic basement — exactly the stratigraphy subsidence predicts and the platform hypothesis does not. The same atoll was the site of the first thermonuclear test that year, which is why the definitive test of a reef theory sits inside a very different history.