Plinian eruption
Short eruptions can end in less than a day. Longer ones can take several days to months. These eruptions begin with clouds of volcanic ash and occasionally pyroclastic flows.  Sometimes the amount of magma erupted is so large that the top of the volcano collapses.  This leaves a caldera behind. Fine ash can deposit over large areas. Plinian eruptions often happen with loud noises, such as those created by Krakatoa.