Runny lava flows out of the fissures under water, cooling and hardening quickly. Since this is all happening undersea, the weight and pressure of the water keep the heavier mass of the lava close to the seafloor. At the point that magma erupts, it’s called lava. The swift upward movement of the magma weakens the stretched terrain under its bulge, eventually creating cracks or fissures through which magma breaks, eventually forming a vent. Because of its relative lightness and low viscosity, it flows quickly. Pockets of superheated magma well up from beneath the crust, causing the floor of the ocean to bulge upward.įact 2: Basalt, a lightweight porous rock in its solid form, is the primary compound forming the volcanic flow of a shield volcano. Magma is created with the melting of underground rock, formed of basalt in the vast furnace of the mantle. We start deep below the bottom of the ocean. Would you like to take a trip on the lava train, traveling from below the earth straight up 30,000 feet or more, then spreading out down the surface of a shield volcano? Let’s go on this impossible journey at 2,500 degrees Fahrenheit. Stratovolcanoes are made up of alternating layers – or strata – of compressed rock, volcanic ash, large stones and boulders, and hardened lava flow. Helens in the U.S., Mount Fuji in Japan, Mount Kilimanjaro in Tanzania, and Italy’s notoriously destructive Mount Vesuvius.įact 1: Cinder cones get their name from their characteristic cone-like shape, which is formed by volcanic ash and cinders. Many of the most iconic volcanoes in the world are stratovolcanoes, including Mount St. Stratovolcanoes, also called composites, are like cinder cone volcanoes on steroids – they are taller, steeper, and more dangerous than other types of volcanoes due to the release of toxic gases. Two of them (cinder cone and stratovolcano) have similar characeristics.Ī cinder cone volcano has steep walls and violent eruptions of lava, as well as pyroclastic material that is thrown into the air and adds to the cinder cone’s rocky, jagged appearance. Volcanology, the scientific study of volcanoes, defines three types of volcanoes on Earth: cinder cone, stratovolcano, and shield. Come on a thrill ride that starts deep beneath the Earth’s surface to see the unique way shield volcanoes erupt. There are shield volcanoes in several parts of the world, including Iceland and the Galápagos Islands, but the largest and most massive of all shield volcanoes actually form the archipelago of Hawai‘i. The shield volcano gets its name from its summit being largely flat and tilted, with a raised section in the center, appearing to some as a warrior’s shield.
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