Phases of caldera formation: (A) the magma chamber fills and begins supplying lava to the volcano, eruptions commence; (B) explosive eruptions begin to exhaust the reservoir of magma, evacuating the upper part of the magma chamber and initiating collapse of the volcano; (C) eruptions cease, the magma chamber cools, final collapse into the depleted magma chamber forms a caldera partially filled with volcanic debris, as water percolates into hot volcanic material, steam explosions are released; and (D) subsequent minor eruptions from the cooling magma chamber build small volcanoes and accumulate volcanic deposits on the caldera floor as the depression gradually fills with water.