What is "eruption column"

n. (context geology English) a cloud of ash emitted during a volcanic eruption

An eruption column is a cloud of hot volcanic ash suspended in volcanic gas emitted during an explosive volcanic eruption. The ash forms a column that may rise many kilometres into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km, penetrating the stratosphere. Stratospheric injection of aerosols by volcanoes is a major cause of short-term climate change.

A common occurrence in explosive eruptions is for column collapse to occur. In this case, the eruption column is too dense to be lifted high into the air by air convection, and instead falls down the flanks of the volcano to form a pyroclastic flow or surge. On some occasions, if ash isn't dense enough to fall, it may create pyrocumulonimbus.