Maars are after cinder cones the second-most common type of volcano. They form when magma interacts explosively with surrounding rocks, excavating broad but shallow craters on the surface. The Espenberg maars are the first known maars to have formed within permafrost; other large maars in permafrost have been found in the Pali-Aike volcanic field of Argentina. Interactions between magma and ice are different than these between lava and ice, as ice conducts heat only slowly and a large amount of energy is consumed during its sublimation; thus its melting and explosive evaporation occurs only slowly.