Volcanic ash

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Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than 2 millimetres (0.079 in) in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruptions and ejection of entrained particles during steam eruptions causing phreatic eruptions. The violent nature of volcanic eruptions involving steam results in the magma and solid rock surrounding the vent being torn into particles of clay to sand size. Volcanic ash can lead to breathing problems, malfunctions in machinery, and from more severe eruptions, years of global cooling.

Ash deposited on the ground after an eruption is known as ashfall deposit. Significant accumulations of ashfall can lead to the immediate destruction of most of the local ecosystem, as well the collapse of roofs on man-made structures. Over time, ashfall can lead to the creation of fertile soils. Ashfall can also become cemented together to form a solid rock called tuff. Over geologic time, the ejection of large quantities of ash can produce an ash cone.

For more information about Volcanic ash, read the full article at Wikipedia.
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News tagged with volcanic ash

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Hundreds of dinosaur nests found in India

Other Sciences / Archaeology & Fossils

Oct 02, 2009 | 4.7 / 5 (12) | 0

(PhysOrg.com) -- Geologists have discovered hundreds of fossilized nests each containing clutches of eight dinosaur eggs. The eggs were located in sand banks in Tamil Nadu in Southern India.

Mt. Redoubt Gives Alaskans a Taste of the Moon

Space & Earth / Earth Sciences

Apr 06, 2009 | 5 / 5 (2) | 1

"It's very fine but angular - the sharp edges make it feel gritty and abrasive."

Alaska's Mount Redoubt has another large eruption

Space & Earth / Earth Sciences

Apr 05, 2009 | 5 / 5 (5) | 3

(AP) -- The Mount Redoubt volcano had another large eruption Saturday after being relatively quiet for nearly a week.

Researcher investigates ancient geology to understand human development, climate change

Space & Earth / Earth Sciences

Oct 03, 2008 | 4.2 / 5 (10) | 0

(PhysOrg.com) -- To figure out how ancient humans adapted to their environment and constructed civilizations, you need to know the environment in which they lived -- including climate change over thousands of years.

Alaska volcano quiets down after making ashy mess

Space & Earth / Earth Sciences

Mar 29, 2009 | 5 / 5 (1) | 0

(AP) -- Alaska's Mount Redoubt has simmered down after spreading a coating of gritty volcanic ash over scores of communities that include the state's largest city of Anchorage.

New tremors at Alaska volcano spewing ash into sky

Space & Earth / Earth Sciences

Mar 24, 2009 | 4 / 5 (1) | 0

(AP) -- New tremors at Alaska's Mount Redoubt are prompting speculation that the volcano could be in a phase that will lead to more instability. The 10,200-foot volcano erupted six times Sunday and Monday, ...