Geography | |
---|---|
Location | Pacific Ocean |
Coordinates | 16°15′S168°7′E / 16.250°S 168.117°E |
Archipelago | New Hebrides |
Area | 677.7 km2 (261.7 sq mi) |
Highest elevation | 1,334 m (4377 ft) |
Administration | |
Vanuatu | |
Province | Malampa |
Demographics | |
Population | 7,275 (2009) |
Ethnic groups | Ni-Vanuatu |
Ambrym | |
---|---|
Highest point | |
Peak | Ambrym Volcano summit |
Elevation | 1,334 m (4,377 ft) [1] |
Listing | Volcanoes of Vanuatu |
Coordinates | 16°15′S168°7′E / 16.250°S 168.117°E [1] |
Dimensions | |
Area | 678 km2 (262 sq mi) |
Geography | |
Geology | |
Mountain type | Pyroclastic shield [1] |
Volcanic arc | New Hebrides arc [1] |
Last eruption | 2022 [2] |
Ambrym is a volcanic island in Malampa Province in the archipelago of Vanuatu. Volcanic activity on the island includes lava lakes in two craters near the summit.
Ambrym (also known as Ambrin, [3] "ham rim" in the Ranon language) [4] was allegedly named by Captain Cook, who is said to have anchored off there in 1774. In fact, his expedition never touched Ambrym.[ citation needed ]
Located near the center of the Vanuatuan archipelago, Ambrym is roughly triangular in shape, about 50 km (31 mi) wide. [5] With 677.7 square kilometres (261.7 sq mi) of surface area, it is the fifth largest island in the country. The summit at the centre of the island is dominated by a desert-like caldera, which covers an area of 100 square kilometres (39 sq mi). [1] With the exception of human settlements, the rest of the island is covered by a dense jungle. [5]
The western part of the island, comprising 17,605 ha of forest, together with gardens around habitation, has been recognised as an Important Bird Area (IBA) by BirdLife International because it supports populations of Vanuatu megapodes, Tanna fruit doves, red-bellied fruit doves, grey-eared honeyeaters, cardinal myzomelas, fan-tailed gerygones, long-tailed trillers, streaked fantails, Melanesian flycatchers, buff-bellied monarchs and Vanuatu white-eyes. [6]
Ambrym is a large basaltic volcano with a 12-km-wide caldera, and is one of the most active volcanoes of the New Hebrides volcanic arc. The caldera is the result of a huge Plinian eruption, which took place around AD 50. Its explosive force is rated 6, the third highest in the Smithsonian Institution's Volcanic Explosivity Index ranks of the largest volcanic explosions in recent geological history. [7]
While at higher elevations cinder cones predominate, the western tip of the island is characterized by a series of basaltic tuff rings, of which the largest is about 1 kilometre (0.62 mi) in diameter. These were produced by phreatic eruptions when magma contacted the water table and water-saturated sediments along the coast. [8] The massive, 1900-year-old, 12 kilometres (7.5 mi) × 8 kilometres (5.0 mi) caldera is the site of two active volcanic cones, Benbow and Marum (also spelled Maroum). [1] Mount Benbow was named after English Admiral John Benbow (1653–1702) by Captain Cook.
Several times a century, Ambrym volcano has destructive eruptions. Mount Benbow last erupted explosively in 1913, destroying the mission hospital at Dip Point. Volcanic gas emissions from this volcano are measured by a Multi-Component Gas Analyzer System, which detects pre-eruptive degassing of rising magmas, improving prediction of volcanic activity. [9]
In March 2017, Google added Marum crater with its lava lakes to Google Streetview. [10] Since the last fissure eruption on 16 Dec 2018, the lava lake has disappeared. [11]
With the neighbouring island of Malakula and a few smaller islands, Ambrym forms Malampa Province. The population of 7,275 inhabitants [12] lives mainly off coconut plantations in the three corners of the island.
Like many islands in Vanuatu, Ambrym has its own Austronesian languages. [13]
In the north:
In the southeast:
In the southwest:
Tourists are attracted by Ambrym's active volcanoes, tropical vegetation, and the customs of the local villagers. They stay in traditional bungalows, as there are no hotels on the island. [4]
The island is served by two airports, Ulei Airport in the southeast and Craig Cove Airport in the southwest.
Ambrym is featured in the 2016 Werner Herzog documentary, Into the Inferno .
A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is gone. 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 each century, the formation of a caldera is a rare event, occurring only a few times per century. Only seven caldera-forming collapses are known to have occurred between 1911 and 2016. More recently, a caldera collapse occurred at Kīlauea, Hawaii in 2018.
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.
Mount Tambora, or Tomboro, is an active stratovolcano in West Nusa Tenggara, Indonesia. Located on Sumbawa in the Lesser Sunda Islands, it was formed by the active subduction zones beneath it. Before 1815, its elevation reached more than 4,300 metres high, making it one of the tallest peaks in the Indonesian archipelago.
Pacaya is an active complex volcano in Guatemala, which first erupted approximately 23,000 years ago and has erupted at least 23 times since the Spanish conquest of Guatemala. It rises to an elevation of 2,552 metres (8,373 ft). After being dormant for over 70 years, it began erupting vigorously in 1961 and has been erupting frequently since then. Much of its activity is Strombolian, but occasional Plinian eruptions also occur, sometimes showering the area of the nearby Departments with ash.
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.
Masaya is a caldera located in Masaya, Nicaragua, 20 km (12 mi) south of the capital Managua. It is Nicaragua's first and largest national park, and one of 78 protected areas of Nicaragua. The complex volcano is composed of a nested set of calderas and craters, the largest of which is Las Sierras shield volcano and caldera. Within this caldera lies a sub-vent, which is Masaya Volcano sensu stricto. The vent is a shield type composing of basaltic lavas and tephras and includes a summit crater. This hosts Masaya caldera, formed 2,500 years ago by an 8 km3 (1.9 cu mi) basaltic ignimbrite eruption. Inside this caldera a new basaltic complex has grown from eruptions mainly on a semi-circular set of vents that include the Masaya and Nindiri cones. The latter host the pit craters of Masaya, Santiago, Nindiri and San Pedro. Observations in the walls of the pit craters indicate that there have been several episodes of cone and pit crater formation.
An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano.
Mount Okmok is the highest point on the rim of Okmok Caldera on the northeastern part of Umnak Island in the eastern Aleutian Islands of Alaska. This 9.3 kilometers (5.8 mi) wide circular caldera truncates the top of a large shield volcano. The volcano is currently rated by the Alaska Volcano Observatory as Aviation Alert Level Green and Volcanic-alert Level Normal.
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.
Hunter Island and Matthew Island are two small and uninhabited volcanic islands in the South Pacific, located 300 kilometres (190 mi) east of New Caledonia and south-east of Vanuatu archipelago. Hunter Island and Matthew Island, 70 km (43 mi) apart, are claimed by Vanuatu as part of Tafea Province, and considered by the people of Aneityum part of their custom ownership, and as of 2007 were claimed by France as part of New Caledonia.
Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified.
Coatepeque Caldera is a volcanic caldera in El Salvador in Central America. The caldera was formed during a series of rhyolitic explosive eruptions between about 72,000 and 57,000 years ago. Since then, basaltic cinder cones and lava flows formed near the west edge of the caldera, and six rhyodacitic lava domes have formed. The youngest dome, Cerro Pacho, formed after 8000 BC.
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.
Nemo Peak is a stratovolcano located at the northern end of Onekotan Island, Kuril Islands, Russia. It is truncated by two nested calderas, with the cone of Nemo Peak itself rising in the southwest end of the youngest caldera and a crater lake partially filling the northeast part, named Ozero Chernoye.
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 Barrier is an active shield volcano located in the north of Kenya. It is last known to have erupted in 1921.
The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over 350 kilometres (220 mi) northwest of the city of Vancouver and about 50 kilometres (31 mi) west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in western Canada, measuring about 30 kilometres (19 mi) long (north-south) and 20 kilometres (12 mi) wide (east-west). Mount Silverthrone, an eroded lava dome on the caldera's northern flank that is 2,864 metres (9,396 ft) high, may be the highest volcano in Canada.
Ceboruco is a dacitic stratovolcano located in Nayarit, Mexico, northwest of the Trans-Mexican Volcanic Belt. The largest eruption, the Jala Plinian eruption, was around 930 AD ±200, VEI 6, releasing 11 cubic kilometres (2.6 cu mi) of tephra. The most recent and best documented eruption from Ceboruco lasted from 1870–1875, with fumarole activity lasting well into the 20th century. The mountain features one large caldera, created during the Jala eruption, with a smaller crater nested inside that formed when the Dos Equis lava dome collapsed during the Coapales eruption around 1100 AD. Within both of these craters, are several explosive volcanic features, including scoria deposits, lava domes, and pyroclastic domes, or cinder cone volcanoes.
Santorini caldera is a large, mostly submerged caldera, located in the southern Aegean Sea, 120 kilometers north of Crete in Greece. Visible above water is the circular Santorini island group, consisting of Santorini, the main island, Therasia and Aspronisi at the periphery, and the Kameni islands at the center. It has been designated a Decade Volcano.