Energy from Magma

Magma dynamics and geothermal energy correspond to different communities of practice by history, the kinds of observations and models involved, and the institutions that support their work. The former has up until now relied on indirect field and laboratory studies and hydrodynamic models. It is largely the domain of curiosity-driven science within academia. The latter has the benefit of abundant direct observations from drilling, and steam has monetary value. It is largely the domain of economically driven science, engineering, and technology within industry. Now that the geothermal quest for hotter fluids has led to unexpected encounters with magma, these two communities need each other. For high temperature geothermal, the size and longevity of the resource is largely determined by the size and proximity of subjacent magma. For a magma reservoir, heat loss and hence behavior are controlled by the superjacent hydrothermal system. A magma body overlain by an actively convecting hydrothermal system will behave very differently from one insulated by dry, impermeable rock. Conversely, extraction of heat from a hydrothermal reservoir using high enthalpy fluids will rapidly deplete the thermal energy contained in solid rock if it is not sitting on a hot plate of magma. Through its relatively small temperature interval of crystallization and associated “second boiling” releasing abundant high enthalpy fluid, magma acts as a material with extremely high heat capacity. Moreover, it is periodically replenished and convects, bringing uncooled magma upward and once cooled below the solidus undergoes thermal cracking, opening large surface areas for heat transfer from crystallized magma to fluid. High enthalpy fluids and magma are complementary halves to the whole of a game-changer in geothermal energy. At Krafla Caldera, Iceland, we are poised to understand this magma-hydrothermal connection.