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Illustrated Volcano Glossary
The most common type of volcanic rock, with a relatively low silica content and typically erupted at shield volcanoes.
Basalt is the usually hard and black volcanic rock formed from (liquid) balsalitc lava. Balsaltic lava contains less than about 52 percent silica (SiO2) by weight. Because of its low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can quickly and easily flow more than 20 km from a vent. The low viscosity typically allows volcanic gases to escape without genera... -> See whole entry
Base surges are ground hugging, fast outward moving and turbulent, dilute clouds of gas and ash. They result from water magma interactions (violent steam explosions). During the 1965 eruption of Taal volcano (Philippines), such base surges were first observed. Some of them traveled 4 km and killed 189 people. Base surges were first identified during ocean nuclear weapons explosions in the Pacific.... -> See whole entry
Volcanology: (volcanic) block
Volcanic blocks are solidified rock fragments greater than 64 mm in diameter. Blocks commonly are ejected during explosive eruptions and consist of older pieces of the volcano's edifice, e.g. parts of the conduit, lava domes or older lava flows.
During violent eruptions, blocks of up to several meter size can be thrown to several km distance. For example, during the Minoan eruption (ca. 1613 BC) of the Santorini volcano in Greece, meter-sized blocks were thrown to up to 7 km horizontal distance and impacted violently into the ground, some of them destroying houses of ancient settlements. The time some of these blocks spent on their trajec... -> See whole entry
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Volcanology: volcanic bomb
Ejected fragments of fresh magma larger than 64 mm in diameter, often shaped aerodynamically during their flight.
Volcanic bombs are lava fragments larger than 64 mm in diameter that were ejected while still viscous and partially molten. Many bombs acquire rounded aerodynamic shapes during their travel through the air. Volcanic bombs include breadcrust bombs, ribbon bombs, spindle bombs (with twisted ends), spheroidal bombs, and "cow-dung" bombs. -> See whole entry
Volcanic bomb with a cracked surface, similar to bread, caused by the slow expansion of the interior gas bubbles while cooling.
A breadcrust bomb is a volcanic bomb with a cracked and checkered surface, sometimes resembling the surface of a loaf of bread. The cracks develop when the outer surface of a partially molten lava fragment cools to form a brittle surface and then subsequently cracks as the hot interior expands due to the continued growth of gas bubbles. -> See whole entry
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More on VolcanoDiscovery:
List and map of all volcanoes in Africa. Most volcanoes are located in the Great Rift Valley, but there are more.
World-wide volcanic activity reports, updated almost daily.
: A third tectonic setting where volcanism occurs is believed to be the result of mantle plumes and not directly related to plate boundaries. So called hot spot volcanoes fall into this category.
Photos from lava lakes in the world: Erta Ale, Nyiragongo, Hawaii, Vanuatu