Composite volcanoes are made of cinders, ash, and lava.These types of volcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata that give rise to the name.Composite volcanoes, also known as stratovolcano, are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris.Mauna Kea, a volcano on the American island of Hawaii, and Mount Etna, a volcano on the Italian island of Sicily, are both covered with hundreds of cinder cones.Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics that build up around the vent.Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown up.Giant shield volcanoes are found on other planets of the Solar System, including Olympus Mons on Mars and Sapas Mons on Venus.They include the largest volcanoes on earth, such as Tamu Massif and Mauna Loa.
However, they are most characteristic of ocean island volcanism associated with hot spots or with continental rift volcanism.Shield volcanoes are found wherever fluid low-silica lava reaches the surface of a rocky planet.Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano’s distinctive form.It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano.A shield volcano is a type of volcano named for its low profile, resembling a warrior’s shield lying on the ground.Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.It is an active shield volcano with relatively gentle slopes, with a volume estimated at 18,000 cubic miles (75,000 km3), although its peak is about 125 feet (38 m) lower than that of its neighbor, Mauna Kea.Scientists say they don’t expect that to happen right away but officials on the Big Island of Hawaii are telling residents to be prepared in case it does erupt soon. The ground is shaking and swelling at Mauna Loa, the largest active volcano in the world, indicating that it could erupt.It hasn’t erupted since 1984 and previous eruptions haven’t posed much of a threat to human settlement, but the largest city, Hilo, is partly built on a lava flow from a 19th century eruption.By comparison, Mauna Loa’s smaller neighbor of Kilauea has persistently erupted for years at a time and posed a much greater danger to human settlement.According to local news reports, more than 300 flights have been delayed because of the eruption.Where Mauna Loa, Hawaii’s biggest volcano, will erupt from Roughly 200,000 people live on the Big Island.Last month, authorities on Hawaii’s Big Island advised residents to prepare a “go bag” in case they needed to evacuate quickly, since there were increasing signs that Mauna Loa would soon erupt. Webcams mounted on the summit caldera of Mokuaweoweo showed a vast fissure had opened in the crater, from which fountains of lava were pouring forth.Later, lava and noxious sulfur dioxide gas began pouring out of vents along the volcano’s northeastern slope and flowing in rivers down the mountain’s gentle slopes.While authorities on the Big Island have said the lava poses no danger to communities at present, they have issued warnings for ashfall and Pele’s hair, a type of fibrous glass formed when lava is stretched thinly as it cools. According to scientists at the US Geological Survey’s Hawaiian Volcano Observatory in Hilo, the eruption began just before midnight on Sunday.
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