Caldera Collapse Structure, Its Importance in Understanding Geothermal Systems

Abstract

Large collapse calderas caused by huge pyroclastic eruptions are thought to have good potential for geothermal development. But the collapse structure and post-caldera volcanism which largely affects post-caldera geothermal systems have a wide variety. Examples such as gravity survey and core geology from Aso and other Japanese calderas give information on caldera structure and caldera-forming and filling processes. The collapse structure of calderas may have wide variation and the location (alignment) and characteristics of post-caldera volcanism can be an indicator of the collapse structure. The size and aspect ratio of magma chamber, and regional tectonic stress may affect the occurrence of these different type collapses. In geothermal potential assessment of caldera volcanoes, estimation based on caldera forming magma chamber tends to over-estimate. Estimation based on post-caldera volcanism is rather realistic.