Related topics: volcano

Unravelling the when, where and how of volcanic eruptions

There are about 1,500 potentially active volcanoes worldwide and about 50 eruptions occur each year. But it's still difficult to predict when and how these eruptions will happen or how they'll unfold. Now, new insight into ...

Do as the Romans: Power plant concrete strengthens with time

A rare mineral that has allowed Roman concrete marine barriers to survive for more than 2,000 years has been found in the thick concrete walls of a decommissioned nuclear power plant in Japan. The formation of aluminous tobermorite ...

Volcano erupts on Hawaii's Big Island, draws crowds to park

Kilauea volcano on Hawaii's Big Island roared back to life Sunday night as lava went shooting into the air, boiling away a water lake and sending a massive plume of steam, gas and ash soaring into the atmosphere.

Thousands flee as Indonesian volcano bursts to life

Thousands have fled the scene of a rumbling Indonesian volcano that burst to life for the first time in several years, belching a massive column of smoke and ash, the disaster agency said Monday.

Insights into climate change during origin of dinosaurs

The Triassic Period, about 252 to 201 million years ago, was a time of volatile change, particularly during an interval known as the Carnian (about 237 to 227 million years ago). Three dramatic events occurred on Earth: the ...

How volcanoes explode in the deep sea

Most volcanic eruptions take place unseen at the bottom of the world's oceans. In recent years, oceanography has shown that this submarine volcanism not only deposits lava but also ejects large amounts of volcanic ash.

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Volcanic ash

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.

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