Eruption column

An eruption column or eruption plume is a tall, powerful cloud of super-heated ash and tephra mixed with gases that shoots into the sky during an explosive volcanic eruption. These columns can rise many kilometers above the volcano, sometimes reaching even higher than 40 km (25 mi) into the stratosphere. When volcanoes erupt in this way, they can send tiny particles called aerosols high into the atmosphere, which can change Earth’s weather and climate change for a short time.

Sometimes, an eruption column can become too heavy to stay floating high up. When this happens, it collapses and falls back down the sides of the volcano. This falling material can turn into fast-moving, dangerous clouds called pyroclastic flows or surges. In other cases, if the material isn’t heavy enough to fall, it can form special storm-like clouds known as pyrocumulonimbus. Eruption columns are one of the most spectacular and powerful shows nature can produce, and they help scientists understand how volcanoes affect our planet.

Formation

Eruption columns form during explosive volcanic eruptions. When volcanoes erupt, gases and other materials in the rising magma cause it to break into tiny pieces of volcanic ash and larger pieces called tephra. These particles are shot into the air at very high speeds and can rise several kilometers above the volcano, pushed upward by strong currents of hot air.

Eruption columns can be short-lived, happening during a single big explosion, or they can last longer if the volcano keeps erupting or has many small explosions close together.

Structure

An eruption column is a tall cloud of hot ash and rocks pushed into the air by a volcanic eruption. Near the bottom, fast-moving gases, mostly steam, shoot the material upward. This part is called the gas thrust region.

Most of the column's height is made up of the convective thrust region, where the rising air mixes with surrounding air, heating it and making it rise. As the column goes higher, it reaches a point where the warm air inside is the same weight as the cold air outside. Here, the material spreads out sideways in what is called the umbrella region.

Column heights

Eruption columns rise until they reach a height where they are the same density as the surrounding air. Their height depends on factors like the size of the volcanic vent, the amount of gas in the magma, and how fast it erupts. Winds and temperature changes in the atmosphere can also affect how high the column goes. The highest eruption columns can reach about 55 km, but most are between 2 and 45 km tall.

When eruption columns grow tall enough, they can break through the tropopause and inject ash into the stratosphere. This ash can stay in the atmosphere for a long time and may even affect global temperatures. For example, after Mount Pinatubo erupted in 1991, world temperatures dropped slightly. The height of an eruption column helps scientists measure how powerful an eruption was.

Hazards

Eruption columns can sometimes become too heavy to stay up in the air. When this happens, the material falls down quickly, forming fast-moving currents of hot ash and gas that can travel down the sides of a volcano at very high speeds. This is one of the biggest dangers during eruptions that create columns.

Eruption columns can also be very dangerous for airplanes. In the past, airplanes have flown through these columns and been badly damaged. The ash can clog engines, cover the cockpit windows, and contaminate fuel. Because of these risks, special centers around the world watch for eruption columns to help keep airplanes safe.