GIANT METEOROID IMPACTS CAN CAUSE VOLCANISM

Abstract

We present a model to assess the viability of the creation of volcanic eruptions of up to flood-basalt size from a giant impactor striking a relatively thin lithosphere. A 300-km-radius crater in 75-km-thick lithosphere can create 10 6 km 3 of magma from instantaneous in situ decompression of mantle material with a potential temperature of 1300 °C. For a range of lithospheric thicknesses and potential temperatures, subsequent adiabatic melting caused by mantle convection beneath the lithosphere at the site of the impact can create additional magma. Though the evidence that a giant impactor has struck at the location of any terrestrial flood-basalt province is equivocal, there are possible age coincidences between evidence for impacts and occurrences of flood basalts. Our model demonstrates that a giant impactor could cause a flood basalt, and this process may have been significant early in Earth history when impactors were more frequent and mantle temperatures likely higher, though other processes are required for at least the majority of flood-basalt provinces today.