A series of diagrams to show how Hawaiian volcanoes have an inherent weakness that can lead to giant landslides (from ideas presented by Dave Clague, USGS). In A, a young volcano erupts pillow lavas on the seafloor; explosive activity is prevented by deep water pressure. In B, the volcano nears the surface; the water pressure no longer prevents explosive mixing of hot lava and seawater, and phreatomagmatic explosions produce a layer of hyaloclastite (yellow). In C, the volcano has grown above sea level so that eruptions no longer encounter seawater; they are not explosive, however, lava flowing into the ocean breaks up and occasionally produces littoral explosions, both of which also generate hyaloclastite. In D, the volcano is continuing to build subaerially; the layers of hyaloclastite are an inherent weakness that may promote giant landslides.