Geothermal Effects of Water Penetrating into Hot Rock Boundaries of Magma Bodies

Abstract

Mass balance studies of ice melted at the subglacial caldera Grimsvotn in Iceland indicate a heat release of 5000 MW from the geothermal system in the caldera region. This heat output has been maintained for several centuries. A magmatic source of heat extraction remain problematic. Field evidence from watering a molten lava flow has demonstrated that water penetrating into the hot rock boundary layer above the solidifying horizon of the lava can release heat at a rate of 40 kw/m2. These observations support theoretical considerations presented by Lister (1974, 1976). We conclude that the penetration of water into the hot rock boundary of solidifying magma bodies offers the most probable explanation for the sustained intense heat release of many geothermal systems. Further, we suggest this process of heat extraction be given consideration in the exploitation of magmatic resources, where the generation of stem might be accelerated by injection of water into the hot rock boundary.