I hear news of "eruptive lava fissures" opening up in Hawaii, nine of them at last count. But I don't understand what these are really.
Are these existing, older lava tubes that are suddenly opening to the surface due to recent filling with new lava, or cracks that go through the crust to to deeper chambers of magma, or something else?
update: I've just seen a the video in the CBS News website's Kilauea volcano eruption: Seismic activity increases, earthquakes strike 5 days in a row (scroll down for this particular video). I wonder if there is a better or more technical visualization of the sources for the fissures somewhere?