A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism.
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and solidifies before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high to intermediate levels of silica, with lesser amounts of less viscous mafic magma. Extensive felsic lava flows are uncommon, but have traveled as far as 15 km (9 mi).
The Ring of Fire is a tectonic belt of volcanoes and earthquakes.
Mount Bachelor, formerly named Bachelor Butte, is a dormant stratovolcano atop a shield volcano in the Cascade Volcanic Arc and the Cascade Range of central Oregon. Named Mount Bachelor because it stands apart from the nearby Three Sisters, it lies in the eastern segment of the central portion of the High Cascades, the eastern segment of the Cascade Range. The volcano lies at the northern end of the 15-mile (24 km) long Mount Bachelor Volcanic Chain, which underwent four major eruptive episodes during the Pleistocene and the Holocene. The United States Geological Survey considers Mount Bachelor a moderate threat, but Bachelor poses little threat of becoming an active volcano in the near future. It remains unclear whether the volcano is extinct or just inactive.
A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.
Mount Mazama is a complex volcano in the western U.S. state of Oregon, in a segment of the Cascade Volcanic Arc and Cascade Range. A volcanic peak once existed, but it collapsed following a major eruption approximately 7,700 years ago, to be replaced by a caldera. The volcano is in Klamath County, in the southern Cascades, 60 miles (97 km) north of the Oregon–California border. Its collapse, due to the eruption of magma emptying the underlying magma chamber, formed a caldera that holds Crater Lake. Mount Mazama originally had an elevation of 12,000 feet (3,700 m), but following its climactic eruption this was reduced to 8,157 feet (2,486 m). Crater Lake is 1,943 feet (592 m) deep, the deepest freshwater body in the U.S. and the second deepest in North America after Great Slave Lake in Canada.
Cerro Negro is an active volcano in the Cordillera de los Maribios mountain range in Nicaragua, about 10 km (6.2 mi) from the village of Malpaisillo. It is a very new volcano, the youngest in Central America, having first appeared in April 1850. It consists of a gravelly basaltic cinder cone, which contrasts greatly with the surrounding verdant hillsides, and gives rise to its name, which means Black Hill. Cerro Negro has erupted frequently since its first eruption. One unusual aspect of several eruptions has been the emission of ash from the top of the cone, while lava erupts from fractures at the base.
Cerro Azul, sometimes referred to as Quizapu, is an active stratovolcano in the Maule Region of central Chile, immediately south of Descabezado Grande. Part of the South Volcanic Zone of the Andes, its summit is 3,788 meters (12,428 ft) above sea level, and is capped by a summit crater that is 500 meters (1,600 ft) wide and opens to the north. Beneath the summit, the volcano features numerous scoria cones and flank vents.
Langila is one of the most active volcanoes of New Britain, Papua New Guinea. It consists of four overlapping volcanic cones on the eastern flank of an older extinct volcano, Talawe. Talawe is the largest volcano in Cape Gloucester. There have been dozens of recorded eruptions since the 19th century from three separate volcanic craters at the summit of Langila. The most recent eruptive cycle of Langila began in August 2006 and continued into early 2007. Volcanic activity at Langila consists of Strombo-Vulcanian and Vulcanian eruptions and lava flows. Langila is one of the most active volcanoes in the Bismark archipelago. The smallest crater is crater number 3.
Mount Balbi is a Holocene stratovolcano located in the northern portion of the island of Bougainville, Papua New Guinea. A gentle prominence at 05°54′09″S154°59′28″E is the highest point of the island. There are five volcanic craters east of the summit, one of which contains a crater lake. The summit is composed of coalesced cones and lava domes which host a large solfatara field. There are numerous fumaroles near the craters, though Balbi has not erupted in historic time.
Billy Mitchell is a pyroclastic shield in the central part of the island of Bougainville, just north-east of the Bagana Volcano in Papua New Guinea. It is a small pyroclastic shield truncated by a 2 km wide caldera filled by a crater lake. It is named after Billy Mitchell, a 20th-century United States Army general who is regarded as the father of the United States Air Force.
Several types of volcanic eruptions—during which material is expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.
Mount Tendürek is a shield volcano on the border of Ağrı and Van provinces in eastern Turkey, near the border with Iran. The volcano, which is mostly known for being near the supposed wreck site of Noah's Ark, is very large; its lava flows cover roughly 650 km2 (251 sq mi) across a swath of flat land. The mountain's two main features are the main summit crater Greater Tendürek, and a smaller crater known as Lesser Tendürek which lies to the east of the main crater. The slopes are very gentle and resemble a shield, after which the type is named. Mount Tendürek is known to have erupted viscous lava like that of volcanoes on the island of Hawaii.
In volcanology, a pyroclastic shield or ignimbrite shield is an uncommon type of shield volcano. Unlike most shield volcanoes, pyroclastic shields are formed mostly of pyroclastic and highly explosive eruptions rather than relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano. They typically display low-angle flank slopes and often have a central caldera caused by large eruptions. Lava is commonly extruded after explosive activity has ended. The paucity of associated Plinian fall deposits indicates that pyroclastic shields are characterized by low Plinian columns.
The Bola volcano, also known as Wangore, is an andesitic stratovolcano, located south-west of the Dakataua caldera in New Britain, Papua New Guinea. It is 1,116 metres (3,661 ft) tall and has a 400 m (1,310 ft) wide summit crater.
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet 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. The volcanic rock resulting from subsequent cooling is also often called lava.
Mt Matavanu is an active volcano on the island of Savai'i in Samoa. The volcano was formed during an eruption in 1905. Lava flows from the eruption covered a large area of land in the Gaga'emauga district, leading to the relocation of several villages.
Anyuyskiy is an extinct volcano in the Anyuy Mountains, Chukotka Autonomous Okrug, Far Eastern Russia. It is formed by two systems: one is formed by long lava flows which disrupted the valley of the Monni River. Later, a volcanic cone formed, experiencing explosive activity and eventually extruding a long lava flow.
A lava cone is a type of volcano composed primarily of viscous lava flows. The volcanic cone can contain a convex profile due to the flank flows of viscous lava.
Aluchin is a volcano along the Aluchin River in the Chukotka Autonomous Okrug of Russia. The volcano was discovered in 1956–1957 by G.K. Kleshchev.
