GEOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -Volcanic ash (also known as tephra) 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.

Detailed explanation-3: -Volcanologists use the word ‘tephra’ as general term for volcanic rock fragments irrespective of grain size produced during an explosive eruption. Volcanic ash is fine tephra, and terms such as lapilli, blocks, and bombs are used to categorize larger fragments.

Detailed explanation-4: -Pyroclastic surges are low-density flows that leave thin but extensive deposits with cross-bedded layering. Ash flows leave deposits known as tuff, which are made up mainly of ash-sized fragments.

Detailed explanation-5: -Pyroclastic density currents are hot, fast moving “clouds” of gas, ash, and rock debris known as tephra. They can reach temperatures up to 1, 000 degrees Celsius and speeds of 700 kilometers per hour and are much denser than the surrounding air.