Thermal control of basaltic fissure eruptions

As hot, basaltic magma rises in a newly opened dyke during an eruption, it flows through colder crustal rock. The flowing magma advects heat along the dyke; at the same time, heat is conducted out of the dyke into the colder surroundings. The loss of heat will lead initially to the channel becoming constricted by magma solidifying against the walls. The channel may then become completely blocked, which will end the eruption at that site before the supply of magma is exhausted. Alternatively, the continual supply of heat by the flowing magma may, after some time, exceed the losses into the country rock. In this case, the initial solidification is reversed, the walls of the channel are progressively melted and the dyke is widened until the supply diminishes. We present here a model that quantitatively delineates these two regimes. We also identify an intermediate regime in which parts of the surface fissure may become blocked and the eruption continues from isolated vents.