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A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.
Volcanoes are generally found where tectonic plates are diverging or converging.
A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together.
By contrast, volcanoes are usually not created where two tectonic plates slide past one another.
Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates.
The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn originates from Vulcan, the name of a god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology.
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth. When first erupted from a volcanic vent, lava is a liquid at temperatures from 700 °C to 1,200 °C (1,300 °F to 2,200 °F).
Manam, known locally as Manam Motu, is an island located in the Bismarck Sea near the coast of mainland Papua New Guinea.
The island was created by the activity of the Manam Volcano, one of the country’s most active.
It was inhabited until 2004, but it is now abandoned and its residents resettled elsewhere in Papua New Guinea.
Mount Fuji is an attractive volcanic cone.
Volcanic cones are among the simplest volcanic formations. They are built by ejects from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption.
Mount Rinjani or Gunung Rinjani is an active volcano in Indonesia on the island of Lombok.
It rises to 12,224 feet, making it the second highest volcano in Indonesia.
On the top of the volcano is a crater lake known as Segara Anak (Child of the Sea). This lake is estimated at being around
600 feet. deep and the area also contains
A phreatic eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma (1,112 to 2,138 °F) causes near-instantaneous evaporation to steam resulting in an explosion of steam, water, ash, rock.
eruptions typically include steam and rock fragments; the inclusion of
lava is unusual.
Mount St. Helens is most famous for its catastrophic eruption on May 18, 1980, which was the deadliest and most economically destructive volcanic event in the history of the United States. Fifty-eight people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed.