Intrusions induce global warming before continental flood basalt volcanism

Extinction events are known to correlate with continental flood basalt eruptions. Massive carbon degassing from these eruptions can have catastrophic impacts on the global climate and biospheres. However, high-precision geochronology from the Deccan Traps and the Columbia River Basalt Group suggests that the onset of global warming precedes the main phase of flood basalt eruptions by several hundred thousand years. Here we construct a numerical model of sill intrusion to investigate this lag between warming and eruptions. The model determines the depth of sill intrusion depending on the evolving crustal density and temperature structures. Main-phase eruptions occur when the average density above the sill intrusion is greater than the magma density. When combined with a carbon-cycle simulation, the models can reproduce the observed timing and amplitude of the global warming events associated with the Deccan Traps and the Columbia River Basalt Group. We therefore conclude that major eruptions of continental flood basalts require densification of the crust by voluminous basaltic magma intrusions. The crystallization of such pre-eruption intrusions could release enough carbon dioxide to drive substantial global warming before the main phase of flood basalt volcanism.