A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have occurred between 1911 and 2018, with a caldera collapse at Kīlauea, Hawaii in 2018. Volcanoes that have formed a caldera are sometimes described as "caldera volcanoes".
The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982.
The Bromo, or Mount Bromo is an active somma volcano, a Hindu pilgrimage site, and part of the Tengger mountains, in East Java, Indonesia. At 2,329 meters (7,641 ft) it is not the highest peak of the massif, but is the most active and famous. The area is one of the most visited tourist destinations in East Java, and the volcano is included in the Bromo Tengger Semeru National Park. The name Bromo comes from the Javanese pronunciation of Brahma, the Hindu god of creation. At the mouth of the crater, there is an idol of Ganesha, the Hindu god of wisdom which is being worshipped by the Javanese Hindus. Mount Bromo is located in the middle of a plain called "Sea of Sand", a nature reserve that has been protected since 1919.
The Volcán de Colima, 3,820 m (12,530 ft), also known as Volcán de Fuego, is part of the Colima Volcanic Complex (CVC) consisting of Volcán de Colima, Nevado de Colima and the eroded El Cántaro. It is the youngest of the three and as of 2015 is one of the most active volcanoes in Mexico and in North America. It has erupted more than 40 times since 1576. One of the largest eruptions was on January 20–24, 1913. Nevado de Colima, also known as Tzapotépetl, lies 5 kilometres (3.1 mi) north of its more active neighbor and is the taller of the two at 4,271 meters. It is the 26th-most prominent peak in North America.
Grímsvötn is an active volcano with a fissure system located in Vatnajökull National Park, Iceland. The central volcano is completely subglacial and located under the northwestern side of the Vatnajökull ice cap. The subglacial caldera is at 64°25′N17°20′W, at an elevation of 1,725 m (5,659 ft). Beneath the caldera is the magma chamber of the Grímsvötn volcano.
Sakurajima is an active stratovolcano, formerly an island and now a peninsula, in Kagoshima Prefecture in Kyushu, Japan. The lava flows of the 1914 eruption connected it with the Ōsumi Peninsula. It is the most active volcano in Japan.
Mount Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara. It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia. It is also the highest point in the Indonesian province of West Nusa Tenggara. Adjacent to the volcano is a 6-by-8.5-kilometre caldera, which is filled partially by the crater lake known as Segara Anak or Anak Laut, due to the color of its water, as blue as the sea (laut). This lake is approximately 2,000 metres (6,600 ft) above sea level and estimated to be about 200 metres (660 ft) deep; the caldera also contains hot springs. The lake and mountain are sacred to the Sasak people and Hindus, and are the site of religious rituals. UNESCO made Mount Rinjani Caldera a part of the Global Geoparks Network in April 2018. Mount Rinjani or Samalas are the largest volcanic eruption in the last 2000 years.
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.
Reventador is an active stratovolcano which lies in the eastern Andes of Ecuador. It lies in a remote area of the national park of the same name, which is Spanish for "exploder". Since 1541, it has erupted over 25 times, although its isolated location means that many of its eruptions have gone unreported.
The Rabaul caldera, or Rabaul Volcano, is a large volcano on the tip of the Gazelle Peninsula in East New Britain, Papua New Guinea, and derives its name from the town of Rabaul inside the caldera. The caldera has many sub-vents, Tavurvur being the most well known for its devastating eruptions over Rabaul. The outer flanks of the highest peak, a 688-metre-high asymmetrical pyroclastic shield, are formed by thick pyroclastic flow deposits. There is no sign of a pyroclastic shield along the rim of the caldera, making the location likely underwater, on the caldera's floor.
The Dubbi Volcano is a stratovolcano located in the Southern Red Sea Region of Eritrea. Its peak elevation is 1,625 m (5,331 ft). There have been four known eruptions. In 1400 lava was determined to have reached the Red Sea while in 1861 ash was thrown over 250 km (160 mi) from the volcano. Two further events were suspected between 1861 and the 20th century.
Erta Ale is a continuously active basaltic shield volcano in the Afar Region of northeastern Ethiopia, which is itself part of the wider Afar Triangle. The volcano is located in the Danakil Depression, an area on the border between Ethiopia and Eritrea that is below sea level. It is the most active of the volcanoes in Ethiopia.
Chaitén is a volcanic caldera 3 kilometres (2 mi) in diameter, 17 kilometres (11 mi) west of the elongated ice-capped Michinmahuida volcano and 10 kilometres (6 mi) northeast of the town of Chaitén, near the Gulf of Corcovado in southern Chile. The most recent eruptive phase of the volcano erupted on 2008. Originally, radiocarbon dating of older tephra from the volcano suggested that its last previous eruption was in 7420 BC ± 75 years. However, recent studies have found that the volcano is more active than thought. According to the Global Volcanism Program, its last eruption was in 2011.
Puyehue and Cordón Caulle are two coalesced volcanic edifices that form a major mountain massif in Puyehue National Park in the Andes of Ranco Province, in the South of Chile. In volcanology this group is known as the Puyehue-Cordón Caulle Volcanic Complex (PCCVC). Four volcanoes constitute the volcanic group or complex, the Cordillera Nevada caldera, the Pliocene Mencheca volcano, Cordón Caulle fissure vents and the Puyehue stratovolcano.
The 2011–2012 Puyehue-Cordón Caulle eruption was a volcanic eruption that began in the Puyehue-Cordón Caulle volcanic complex in Chile on 4 June 2011. The eruption, which occurred from the Cordón Caulle fissure after 51 years of the volcano being inactive, is one of the largest volcanic eruptions of the 21st century thus far. At least 3,500 people were evacuated from nearby areas, while the ash cloud was blown across cities all around the Southern hemisphere, including Bariloche, Buenos Aires, Montevideo, Stanley, Porto Alegre, Cape Town, Hobart, Perth, Adelaide, Sydney, Melbourne, Wellington, Auckland and Port Moresby, forcing airlines to cancel hundreds of international and domestic flights and causing travel chaos.
The 2011 Nabro eruption was an eruption of the Nabro stratovolcano in the Southern Red Sea Region of Eritrea, which began on 12 June 2011 after a series of earthquakes. The eruption killed seven and possibly a further 31 people and is estimated to be the highest altitude injection of sulfur dioxide (SO2) ever observed by satellite. The Mount Pinatubo eruption 20 years earlier emitted ten times more SO2. The ash cloud from the eruption reached altitudes which disrupted airline traffic in the region. Until the eruption began, the volcano had no records of historical eruptions.
Mallahle is a stratovolcano on the border of Ethiopia and Eritrea, with a 6 km wide caldera.
Sork Ale is a sicilic stratovolcano located in the Danakil Horst at the southern end of the Danakil Alps near the Ethiopia/Eritrea border. It makes up part of the Bidu volcanic complex.
Events in the year 2011 in Eritrea.
