A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano 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 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.
Vulkaneifel is a district (Kreis) in the northwest of the state Rhineland-Palatinate, Germany. It is the least densely populated district in the state and the fourth most sparsely populated district in Germany. The administrative centre of the district is in Daun. Neighboring districts are Euskirchen, Ahrweiler, Mayen-Koblenz, Cochem-Zell, Bernkastel-Wittlich, and Bitburg-Prüm.
Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano.
The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes in the field have produced a diverse array of maars, tuff rings, scoria cones, and lava flows. With the exception of Rangitoto, no volcano has erupted more than once, but the other eruptions lasted for various periods ranging from a few weeks to several years. Rangitoto erupted several times and recently twice; in an eruption that occurred about 600 years ago, followed by a second eruption approximately 50 years later. The field is fuelled entirely by basaltic magma, unlike the explosive subduction-driven volcanism in the central North Island, such as at Mount Ruapehu and Lake Taupō.
A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe associated with a gaseous explosion. When magma rises up through a crack in Earth's crust and makes contact with a shallow body of groundwater, rapid expansion of heated water vapor and volcanic gases can cause a series of explosions. A relatively shallow crater is left, and a rock-filled fracture in the crust. Where diatremes breach the surface they produce a steep, inverted cone shape.
Laacher See, also known as Lake Laach or Laach Lake, is a volcanic caldera lake with a diameter of 2 km (1.2 mi) in Rhineland-Palatinate, Germany, about 24 km (15 mi) northwest of Koblenz, 37 km (23 mi) south of Bonn, and 8 km (5.0 mi) west of Andernach. It is in the Eifel mountain range, and is part of the East Eifel volcanic field within the larger Volcanic Eifel. The lake was formed by a Plinian eruption approximately 13,000 years BP with a Volcanic Explosivity Index (VEI) of 6, on the same scale as the Pinatubo eruption of 1991. The volcanic discharge observable as mofettas on the southeastern shore of the lake are signs of dormant volcanism.
Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions contain juvenile (magmatic) clasts. It is common for a large explosive eruption to have magmatic and phreatomagmatic components.
The Volcanic Eifel or Vulkan Eifel, also known as the East Eifel Volcanic Field (EEVF), is a region in the Eifel Mountains in Germany that is defined to a large extent by its volcanic geological history. Characteristic of this volcanic field are its typical explosion crater lakes or maars, and numerous other signs of volcanic activity such as volcanic tuffs, lava streams and volcanic craters like the Laacher See. The Volcanic Eifel is still volcanically active today. One sign of this activity is the escaping gases in the Laacher See.
The Auckland Region of New Zealand is built on a basement of greywacke rocks that form many of the islands in the Hauraki Gulf, the Hunua Ranges, and land south of Port Waikato. The Waitākere Ranges in the west are the remains of a large andesitic volcano, and Great Barrier Island was formed by the northern end of the Coromandel Volcanic Zone. The Auckland isthmus and North Shore are composed of Waitemata sandstone and mudstone, and portions of the Northland Allochthon extend as far south as Albany. Little Barrier Island was formed by a relatively isolated andesitic volcano, active around 1 to 3 million years ago.
The Volcano Park in Mayen-Koblenz is a geopark in the rural district of Mayen-Koblenz in the eastern Vulkan Eifel, Germany. It was founded in 1996 and wraps around the Laacher See. Together with the Volcano Park, Brohltal/Laacher See and the Vulkan Eifel Nature and Geo-Park, it forms part of the national Eifel Volcano Land Geo-Park. The three parks are connected by the 280-kilometre-long German Volcano Route.
The Pulvermaar is a water-filled maar that lies southeast of Daun in the German state of Rhineland-Palatinate. Together with the Holzmaar it is one of the Gillenfeld maars.
The Dreiser Weiher near Dreis-Brück in the vicinity of Daun in the German state of Rhineland-Palatinate is a tub-shaped maar in the Eifel mountains. It is up to 1,360 metres long and 1,160 metres wide. It is the second largest maar in the Eifel.
The Mosbrucher Weiher, also called the Mosbrucher Maar, is a silted up maar east of the municipal boundary of the village of Mosbruch in the county Vulkaneifel in Germany. It is located immediately at the foot of the 675-metre-high Hochkelberg, a former volcano. The floor of the maar is in the shape of an elongated oval and is about 700×500 metres in size, its upper boundary has a diameter of about 1,300 × 1,050 metres. This makes the Mosbrucher Maar the third largest of the maars in the western Eifel region. The Üßbach stream flows past and close to the Mosbrucher Weiher.
Bayuda volcanic field is a volcanic field in Sudan, within the Bayuda Desert. It covers a surface of about 11 by 48 kilometres and consists of a number of cinder cones as well as some maars and explosion craters. These vents have erupted 'A'ā lava flows.
A crater is a landform consisting of a hole or depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described as: "a bowl-shaped pit that is formed by a volcano, an explosion, or a meteorite impact". On Earth, craters are "generally the result of volcanic eruptions", while "meteorite impact craters are common on the Moon, but are rare on Earth".
Lunar Crater volcanic field is a volcanic field in Nye County, Nevada. It lies along the Reveille and Pancake Ranges and consists of over 200 vents, mostly small volcanic cones with associated lava flows but also several maars, including one maar named Lunar Crater. Some vents have been eroded so heavily that the structures underneath the volcanoes have been exposed. Lunar Crater itself has been used as a testing ground for Mars rovers and as training ground for astronauts.
Lake Rotokawau is a small volcanic lake 4.1 km (2.5 mi) east of Lake Rotorua in the Bay of Plenty region of New Zealand's North Island. The name is also used for lakes in the Kaipara District, Chatham Islands, on Aupouri Peninsula and near Lake Waikare in Waikato. Access is via Lake Rotokawau Road, from SH30 at Tikitere. The lake is owned and managed by Ngāti Rangiteaorere.
The Navajo volcanic field is a monogenetic volcanic field located in the Four Corners region of the United States, in the central part of the Colorado Plateau. The volcanic field consists of over 80 volcanoes and associated intrusions of unusual potassium-rich compositions, with an age range of 26.2 to 24.7 million years (Ma).
