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".
Santorini, officially Thira and Classical Greek Thera, is a Greek island in the southern Aegean Sea, about 200 km (120 mi) southeast from its mainland. It is the largest island of a small, circular archipelago formed by the Santorini caldera. It is the southernmost member of the Cyclades group of islands, with an area of approximately 73 km2 (28 sq mi) and a 2021 census population of 15,480. The municipality of Santorini includes the inhabited islands of Santorini and Therasia, as well as the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi and Christiana. The total land area is 90.623 km2 (34.990 sq mi). Santorini is part of the Thira regional unit.
The Ring of Fire is a tectonic belt of volcanoes and earthquakes.
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.
Therasia, also known as Thirasía, is an island in the volcanic island group of Santorini in the Greek Cyclades. It lies north-west of Nea Kameni, a small island formed in recent centuries by volcanic activity and thus marking the centre of the island group. Therasia is the second largest island of the group, the largest by far being Thera.
The Minoan eruption was a catastrophic volcanic eruption that devastated the Aegean island of Thera circa 1600 BCE. It destroyed the Minoan settlement at Akrotiri, as well as communities and agricultural areas on nearby islands and the coast of Crete with subsequent earthquakes and paleotsunamis. With a Volcanic Explosivity Index (VEI) of between 6 and 7, it resulted in the ejection of approximately 28–41 km3 (6.7–9.8 cu mi) of dense-rock equivalent (DRE), the eruption was one of the largest volcanic events in human history. Since tephra from the Minoan eruption serves as a marker horizon in nearly all archaeological sites in the Eastern Mediterranean, its precise date is of high importance and has been fiercely debated among archaeologists and volcanologists for decades, without coming to a definite conclusion.
Christiana is a group of three volcanic Greek islands in the Cyclades. The group is located about 16 km southwest of Santorini and is made up of the islands Christiani, Eschati (Εσχάτη) and Askania (Ασκανιά) belonging to the same submarine volcanic edifice, which is assumed to have been dormant since the Early Pleistocene. The island's area is about 2.35 km2. All three islands are now uninhabited but on Christiani there are remains of human settlement dating back to Neolithic times. Christiana islands have been uninhabited since the 1890s and have remained unfarmed since then. As a result, artificial pesticides and fertilizers are absent from this ecosystem. In the mid 1970s, the largest island, Christiani, was considered by NATO as a military base intended to host a missile silo, but this never came to pass. These islands are privately owned and public access is restricted.
Nea Kameni is a small, uninhabited Greek island of volcanic origin located in the Aegean Sea, within the flooded Santorini caldera. Nea Kameni and the neighbouring small island Palea Kameni have formed over the past two millennia through repeated eruptions of dacite lava and ash. The Roman historian Cassius Dio records in the year 47 CE "This year a small islet, hitherto unknown, made an appearance close to the island of Thera." Cassius' report may refer to Palaia Kameni. Pliny the Elder reports a new island emerging on July 8, in the year of the consulship of M. Junius Silanus and L. Balbus, thus 19 CE.
The Yellowstone Plateau Volcanic Field, also known as the Yellowstone Supervolcano or the Yellowstone Volcano, is a complex volcano, volcanic plateau and volcanic field located mostly in the western U.S. state of Wyoming but also stretches into Idaho and Montana. It is a popular site for tourists.
Quetrupillán is a stratovolcano located in Los Ríos Region of Chile. It is situated between Villarrica and Lanín volcanoes, within Villarrica National Park. Geologically, Quetrupillán is located in a tectonic basement block between the main traces of Liquiñe-Ofqui Fault and Reigolil-Pirihueico Fault.
Torfajökull is a rhyolitic stratovolcano, with a large caldera capped by a glacier of the same name and associated with a complex of subglacial volcanoes. Torfajökull last erupted in 1477 and consists of the largest area of silicic extrusive rocks in Iceland. This is now known to be due to a VEI 5 eruption 55,000 years ago.
The geology of the Pacific Northwest includes the composition, structure, physical properties and the processes that shape the Pacific Northwest region of North America. The region is part of the Ring of Fire: the subduction of the Pacific and Farallon Plates under the North American Plate is responsible for many of the area's scenic features as well as some of its hazards, such as volcanoes, earthquakes, and landslides.
Kolumbo is an active submarine volcano in the Aegean Sea in Greece, about 8 km northeast of Cape Kolumbo, Santorini island. The largest of a line of about twenty submarine volcanic cones extending to the northeast from Santorini, it is about 3 km in diameter with a crater 1.5 km across. It first noticed by humans when it breached the sea surface in 1649-50. The Smithsonian Institution's Global Volcanism Program treats it as part of the Santorini volcano, though at least one source maintains that it is a separate magmatic system.
The South Aegean Volcanic Arc is a volcanic arc in the South Aegean Sea formed by plate tectonics. The prior cause was the subduction of the African Plate beneath the Eurasian Plate, raising the Aegean arc across what is now the North Aegean Sea. It was not yet the sea, nor an arc, or at least not the one it is today, nor was there a chain of volcanoes. In the Holocene, the process of back-arc extension began, probably stimulated by pressure from the Arabian Plate compressing the region behind the arc. The extension deformed the region into its current configuration. First, the arc moved to the south and assumed its arcuate configuration. Second, the Aegean Sea opened behind the arc because the crust was thinned and weakened there. Third, magma broke through the thinned crust to form a second arc composed of a volcanic chain. And finally, the Aegean Sea Plate broke away from Eurasia in the new fault zone to the north.
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.
Mikro Profitis Ilias is a ridge on the Greek island of Santorini. The non-volcanic ridge was greatly expanded by the geological activity of the nearby Santorini caldera.
Aspronisi is an uninhabited island lying within the Santorini caldera. The island was originally formed by the massive Minoan eruption in the 2nd millennium BC, after which it was gradually built up by successive volcanic activity. The name Aspronisi, which means 'White Island' in Greek, is derived from the island being partially composed of white pumice.
Palea Kameni, also known as Palia Kameni, is a volcanic island within the Santorini Caldera. The island was formed by a series of volcanic eruptions that formed large deposits of pumice and dacite lavas. The island's name translates to "Old Burnt Island". Palea Kameni is a private island, it was inhabited until it was bought in 1899 and sold in 1975.
