Dangers of Volcanic Ash

Many of the people in Pompeii died from volcanic ash. I wondered how ash could kill someone; couldn't they just leave if the ash became unbearable? That was before I understood the composition of the ash, and how it affects people and things.

When the ash is expelled from a volcano, it can form a cloud. This cloud can rise as a plume (composed of ash and steam) very high into the atmosphere, then fall (what goes up, must come down). Volcanic ash is hard and abrasive. Today it even causes scratches on airplane windows as ash is released from volocanic activity.

Example of what volcanic ash can do:
In 1989 there was an eruption at Mount Redoubt, a volcano in Alaska.

After this explosion a KLM Boeing 747 (flight 867) carrying 240 passengers unknowingly flew through an ash cloud at 26,000 feet. The pilot applied full power, hoping to climb above the plume. Instead, all four engines stopped. The plane dropped to an altitude of 13,000 feet before pilots were able to get the engines started again. The plane did land safely in Anchorage, but the cost repair to the plane was $80 MILLION. The cost was so high because all four engines had to be replaced.

It turns out that the engines were covered with glassy coatings - or resolidified melted ash. When full power was applied to the engines, they became hotter than the melting temperature of the ash, which then turned the ash into a sort of glass coating.

Today the airline industry has a standard procedure of reducing power if a plane comes in contact with volcanic ash plumes. That is, of course, assuming that the plane could not simply go around it.

Because volcanic ash does not dissolve, breathing it (especially over an extended period of time) can cause respiratory failure. The ash from Vesuvius covered a large area, not just Pompeii, but all the area surrounding it; in other words, Pompeii's escape route. This explains a little about how so many people died as a result of falling ash in Pompeii - suffocation -which also explains why the bodies uncovered were not damaged from falling rock.

(photograph shows an ash plume from Mt. Cleveland, Alaska, May 2006)


For more information on the modern-day dangers of vocanic ash, visit the ALPA Fact Sheet: Volcanic Ash Hazards to Airliners