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Subsidence crater

From Biocrawler, the free encyclopedia.

Post-shot subsidence crater and Huron King test chamber, which was less than 20 kilotons (1980)

A subsidence crater is the crater left on the surface of an area which has had an underground (usually nuclear) explosion. Many such craters are present at the Nevada Test Site, which is no longer in use for nuclear testing.

Subsidence craters are created as the "roof" of the cavity caused by the explosion collapses. This causes the surface to depress into a "sink" (which subsidence craters are sometimes called). It is possible for further collapse to occur from the sink into the explosion chamber. When this collapse reaches the surface, and the chamber is exposed atmospherically to the surface, it is referred to as a chimney.

It is at the point that a chimney is formed that radioactive fallout may reach the surface.

At the Nevada Test Site, depths of 100 to 500 meters were used for tests.