Lava can burst out of these fissures without warning ... Dikes are tabular or sheet-like bodies of magma that cut through and across the layering of adjacent rocks and then solidify.

If there's no magma ocean, where does the 'melt' come from that emerges from the volcanoes as lava? Jupiter's volcanic moon Io doesn't appear to have a subsurface ocean of magma, resolving some ...