Veniaminof

Explosive eruptions eject fragmental material that drops from the eruption column, producing pyroclastic-fall deposits. The surface of the glacier in this 1983 photo of Alaska's Veniaminof volcano is darkened by ash. The grain size of the pyroclastic-fall fragments (collectively referred to as tephra) generally decreases away from the vent as larger and denser fragments fall first. The distribution of pyroclastic-fall deposits is influenced by wind direction. Eruptions much stronger than this one can distribute tephra hundreds of km or more from the volcano.