DOUBLE FLOOD BASALTS AND PLUME HEAD SEPARATION AT THE 660-KILOMETER DISCONTINUITY

Several of the world's flood basalt provinces display two distinct tim es of major eruptions separated by between 20 million and 90 million y ears. These double flood basalts may occur because a starting mantle p lume head can separate from its trailing conduit upon passing the inte rface between the upper mantle and the lower mantle. This detached plu me head eventually triggers the first flood basalt event. The remainin g conduit forms a new plume head, which causes the second eruptive eve nt. The second plume head is predicted to arrive at the lithosphere at least 10 million years after the first plume head, in general agreeme nt with observations regarding double flood basalts.