Temperature and Response Time of Magma Hydrothermal Systems, with an Example from Kilauea, Hawaii

Abstract

The time required for cooling of a rapidly emplaced magma body is inversely related to the vigor of hydrothermal circulation, as quantified by the Rayleigh number. Yet, many, if not most, silicic volcanic centers persist much longer than the thermal pulse created by invasion and cooling any single magma body. Accordingly, it seems appropriate to consider the thermal characteristics of a system continuously resupplied with magmatic heat. In this scheme, temperature evolves toward steady-state values that balance the rate of heat input and removal, the former by continuous intrusion of magma and the latter by conduction and ground-water convection. The time required to reach steady-state, which we refer to as the response time, is inversely proportional to the square-root of a .heat-flux. Rayleigh number, which differs from the Rayleigh number used to examine cooling of a rapidly emplaced magma body. Steady-state temperatures themselves exhibits the same proportionality.