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ENCYCLOPEDIC ENTRY

ENCYCLOPEDIC ENTRY

Volcanic Ash

Volcanic Ash

Volcanic ash is a mixture of rock, mineral, and glass particles expelled from a volcano during a volcanic eruption.


Grades

5 - 8

Subjects

Earth Science, Geography, Geology

Image

shoveling volcanic ash

Removing volcanic ash can be a difficult and laborious process. Here, two Icelanders shovel volcanic ash from a hillside in Vestmannaeyjar, a volcanic archipelago off the southwest coast of Iceland.

Photograph by Robert S. Patton

Volcanic ash is a mixture of rock, mineral, and glass particles expelled from a volcano during a volcanic eruption. The particles are very small—less than 2 millimeters in diameter. They tend to be pitted and full of holes, which gives them a low density. Along with water vapor and other hot gases, volcanic ash is part of the dark ash column that rises above a volcano when it erupts.

Due to their tiny size and low density, the particles that make up volcanic ash can travel long distances, carried by winds. When an ash column is moved about by wind, it is called an ash plume. Eventually the ash in the sky falls to the ground. It may create a thick layer of dust-like material on surfaces for miles around the original eruption.

Unlike the ash produced by burning wood and other organic materials, volcanic ash can be dangerous. Its particles are very hard and usually have jagged edges. As a result, it can cause eye, nose, and lung irritation, as well as breathing problems. While in the air, ash can cause problems for jet engines, forcing airlines to cancel flights through the affected area. An ashfall that leaves a thick layer of ash may cause roofs to collapse, clog gutters, and interfere with air conditioning units. Animals in an area coated by volcanic ash may have difficulty finding food, as the plants in the region may be covered in ash. Ash can also contaminate water supplies.


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Director
Tyson Brown, National Geographic Society
Author
National Geographic Society
Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
other
Last Updated

May 20, 2022

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