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cognate or accessory particles – older volcanic rocks from the same volcano accidental particles – derived from the rocks under the volcano These particles may vary in size; tephra can range from ash (< 1 / 10 inch [0.25 cm]) or lapilli (little stones from 1 / 10 to 2 + 1 ⁄ 2 inches or 0.25 to 6.35 centimetres) to volcanic bombs (>2.5 ...
Scoria or cinder is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts. [1] [2] It is typically dark in color (brown, black or purplish-red), and basaltic or andesitic in composition.
Lava is molten or partially molten rock that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust , on land or underwater, usually at temperatures from 800 to 1,200 °C (1,470 to 2,190 °F).
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. [1] [2] Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sandstone). [3]
Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface. Eruptions associated with subducting zones , meanwhile, are driven by subducting plates that add volatiles to the rising plate, lowering its melting point .
The latest bursts of molten rock, ash and toxic gas from Kilauea Volcano on the Big Island of Hawaii are part of an ever changing and still largely mysterious cycle of eruptions that have been at ...
Bright orange molten rock spewed from cracks in the ground in the Reykjanes peninsula and lava crossed a road near the Blue Lagoon - a luxury geothermal spa - which had to close due to the eruption.
Mount Vesuvius violently ejected a cloud of super-heated tephra and gases to a height of 33 km (21 mi), ejecting molten rock, pulverized pumice and hot ash at 1.5 million tons per second, ultimately releasing 100,000 times the thermal energy of the atomic bombings of Hiroshima and Nagasaki.