Detonations significantly below ground level or deep below the water (for instance, nuclear depth charges) also do not produce mushroom clouds, as the explosion causes the vaporization of a huge amount of earth and water in these instances, creating a bubble which then collapses in on itself; in the case of a less deep underground explosion, this produces a subsidence crater. Detonations underwater but near the surface produce a pillar of water, which, in collapsing, forms a cauliflower-like shape, which is easily mistaken for a mushroom cloud (such as in the well-known pictures of the "Crossroads Baker" test). Underground detonations at low depth produce a mushroom cloud and a base surge, two different distinct clouds. The amount of radiation vented into the atmosphere decreases rapidly with increasing detonation depth.