Earth Planets Space, Vol. 57 (No. 11), pp. e17-e20, 2005E-LETTER
Shigekazu Kusumoto1 and Keiji Takemura2
1School of Marine Science and Technology, Tokai University, 3-20-1 Shimizu-ku, Orido, Shizuoka 424-8610, Japan
2Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Noguchibaru, Beppu, Oita 874-0903, Japan
(Received May 20, 2005; Revised September 10, 2005; Accepted September 12, 2005)
The depth of the magma chamber is shown to be an important factor governing the initial type, scale, and collapse of a caldera. The collapse of the magma chamber is approximated by the contraction of a sphere in an elastic medium, and the distribution of plastic and/or rupturing area on the surface is calculated using the Coulomb failure criterion under the assumption of an elastic-perfectly plastic material. It is found that the necessary contraction for the formation of a caldera is described by fifth-power polynomial expression of the depth of the magma chamber, and that the radius and geometry of the caldera are dependent on the depth of the magma chamber.
Key words: Caldera, magma chamber, caldera geometry, depth of magma chamber, numerical simulation.