Volcanic ash

Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter.[1] The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as tephra), including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away.

Ash cloud from the 2008 eruption of Chaitén volcano, Chile, stretching across Patagonia from the Pacific to the Atlantic Ocean
Ash plume rising from Eyjafjallajökull on April 17, 2010
Volcanic ash deposits on a parked McDonnell-Douglas DC-10-30 during the 1991 eruption of Mount Pinatubo, causing the aircraft to rest on its tail. While falling ash behaves in a similar manner to snow, the sheer weight of deposits can cause serious damage to buildings and vehicles, as seen here, where the deposits were able to cause the 120 ton airliner's centre of gravity to shift.
Ash plume from Mt Cleveland, a stratovolcano in the Aleutian Islands

Due to its wide dispersal, ash can have a number of impacts on society, including animal and human health, disruption to aviation, disruption to critical infrastructure (e.g., electric power supply systems, telecommunications, water and waste-water networks, transportation), primary industries (e.g., agriculture), buildings and structures.


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This article uses material from the Wikipedia article Volcanic ash, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.