Maar - a small volcano with wide diameter relative to its height, often with a bowl-shaped crater.
magma - molten rock with contained gases that forms within or somewhat below the earth's crust. It is ejected in highly explosive eruptions to form pyroclasts or lava flows.
magmatic eruption - an explosive eruption from the sudden expansion of magma from internal gas pressure.
nuèe ardente - a hot, heavier-than-air, turbulent "volcanic hurricane" composed of a mixture of hot gases and solid particles. Nuèes ardentes flow rapidly down the slopes of a volcano, ofren attaining speeds fifty to one hundred miles an hour.Such flows commonly form in two parts, a lower "glowing avalance" and an upper "glowing cloud."
pahoehoe lava - lava that has a smooth surface after cooling, compared with the roughness of aa.
Pelèan eruption - an eruption that produces a nuèe ardente, such as that at Mount Pele in 1902.
Plinian eruption - an eruption that forms ash clouds above the volcano to heights as much as thirty miles into the atmosphere. (Named after the eruption of Mount Vesuvius in 72 AD that killed Pliny the elder.)
pumice - a glass foam formed by frothing gas-rich magma. Pumice is very light weight and can float in water.
pyroclastic - refers to the fragmental materials formed by explosive processes of volcanoes.
pyroclastic flow: a heavier-than-air, hurricane-like, non-turbulent cloud of volcanic particles mixed with hot gases, more dense than a pyroclastic flow.
pyroclastic surge - a heavier-than-air, hurricane-like, turbulent cloud of volcanic particles mixed with hot gases, less dense than a pyroclastic flow.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
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