Oregon“A caldera is a large volcanic depression, at least 1km in diameter and often much more, that is enclosed by nearly vertical walls facing into a central flattish floor” (Brown 1970). They are so beautiful that it is hard to imagine that they have been produced by some of the most catastrophic events on Earth. Many develop within the space of a few hours. Huge volumes of material are erupted and huge volumes of material sink into the crust. At least ten caldera forming eruptions in the past 10,000 years have been ejected more than 50km of ash and pumice. Calderas fortunately are not formed very often and only two or three are created every century.Hydrovolcanic landformsHydrovolcanic landforms develop when an external source of water interacts with magma approaching the Earth’s surface. The large areas covered by water, ice, snow, the frozen ground, abundant precipitation, subsurface qualifiers, all combine to ensure that some interaction between water and magma....
