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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.
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous. Tuff composed of sandy volcanic material can be referred to as volcanic sandstone.
Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent to granite.
Andesite is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.
The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the Iceland Plateau and the island of Iceland.
Mount Price is a small stratovolcano in the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada. It has an elevation of 2,049 metres and rises above the surrounding landscape on the western side of Garibaldi Lake in New Westminster Land District. The mountain contains a number of subfeatures, including Clinker Peak on its western flank, which was the source of two thick lava flows between 15,000 and 8,000 years ago that ponded against glacial ice. These lava flows are structurally unstable, having produced large landslides as recently as the 1850s. A large provincial park surrounds Mount Price and other volcanoes in its vicinity. It lies within an ecological region that surrounds much of the Pacific Ranges.
The Table, sometimes called Table Mountain, is a 2,021-metre (6,631 ft) high flow-dominated andesite tuya located 4 kilometres (2 mi) south of Garibaldi Lake, 15 kilometres (9 mi) northeast of Cheekye and 5 kilometres (3 mi) north of Mount Garibaldi, British Columbia, Canada. It rises over 530 metres (1,740 ft) above the surface of Garibaldi Lake, which lies less than 1 kilometre (1 mi) to the north.
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.
Level Mountain is a large volcanic complex in the Northern Interior of British Columbia, Canada. It is located 50 kilometres north-northwest of Telegraph Creek and 60 kilometres west of Dease Lake on the Nahlin Plateau. With a maximum elevation of 2,164 metres , it is the second-highest of four large complexes in an extensive north–south trending volcanic region. Much of the mountain is gently-sloping; when measured from its base, Level Mountain is about 1,100 metres tall, slightly taller than its neighbour to the northwest, Heart Peaks. The lower, broader half of Level Mountain consists of a shield-like structure while its upper half has a more steep, jagged profile. Its broad summit is dominated by the Level Mountain Range, a small mountain range with prominent peaks cut by deep valleys. These valleys serve as a radial drainage for several small streams that flow from the mountain. Meszah Peak is the only named peak in the Level Mountain Range.
Volcanic activity is a major part of the geology of Canada and is characterized by many types of volcanic landform, including lava flows, volcanic plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes, and maars, along with less common volcanic forms such as tuyas and subglacial mounds.
The Strand Fiord Formation is a Late Cretaceous volcanic component, located on northwestern and west-central Axel Heiberg Island, Nunavut, Canada. The formation contains flood basalts which are found on western Axel Heiberg Island at Dragon Cliff 300 m (980 ft) tall.
The High Arctic Large Igneous Province (HALIP) is a Cretaceous large igneous province in the Arctic. The region is divided into several smaller magmatic provinces. Svalbard, Franz Josef Land, Sverdrup Basin, Amerasian Basin, and northern Greenland are some of the larger divisions. Today, HALIP covers an area greater than 1,000,000 km2 (390,000 sq mi), making it one of the largest and most intense magmatic complexes on the planet. However, eroded volcanic sediments in sedimentary strata in Svalbard and Franz Josef Land suggest that an extremely large portion of HALIP volcanics have already been eroded away.
The North Atlantic Igneous Province (NAIP) is a large igneous province in the North Atlantic, centered on Iceland. In the Paleogene, the province formed the Thulean Plateau, a large basaltic lava plain, which extended over at least 1.3 million km2 (500 thousand sq mi) in area and 6.6 million km3 (1.6 million cu mi) in volume. The plateau was broken up during the opening of the North Atlantic Ocean leaving remnants preserved in north Ireland, west Scotland, the Faroe Islands, northwest Iceland, east Greenland, western Norway and many of the islands located in the north eastern portion of the North Atlantic Ocean. The igneous province is the origin of the Giant's Causeway and Fingal's Cave. The province is also known as Brito–Arctic province and the portion of the province in the British Isles is also called the British Tertiary Volcanic Province or British Tertiary Igneous Province.
Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian to late Amazonian, indicating that the planet has been volcanically active throughout its history, and some speculate it probably still is so today. Both Earth and Mars are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occurred on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks and minerals.
The Sverdrup Basin Magmatic Province is a large igneous province located on Axel Heiberg Island and Ellesmere Island, Nunavut, Canada near the rifted margin of the Arctic Ocean at the end of Alpha Ridge.
The volcanology of Eastern Canada includes the hundreds of volcanic areas and extensive lava formations in Eastern Canada. The region's different volcano and lava types originate from different tectonic settings and types of volcanic eruptions, ranging from passive lava eruptions to violent explosive eruptions. Eastern Canada has very large volumes of magmatic rock called large igneous provinces. They are represented by deep-level plumbing systems consisting of giant dike swarms, sill provinces and layered intrusions. The most capable large igneous provinces in Eastern Canada are Archean age greenstone belts containing a rare volcanic rock called komatiite.
Volcanism of Northern Canada has produced hundreds of volcanic areas and extensive lava formations across Northern Canada. The region's different volcano and lava types originate from different tectonic settings and types of volcanic eruptions, ranging from passive lava eruptions to violent explosive eruptions. Northern Canada has a record of very large volumes of magmatic rock called large igneous provinces. They are represented by deep-level plumbing systems consisting of giant dike swarms, sill provinces and layered intrusions.
Jack Gordon Souther was an American-born Canadian geologist, volcanologist, professor and engineer. He contributed significantly to the early understanding of recent volcanic activity in the Canadian Cordillera. Many of his publications continue to be regarded as classics in their field, even now several decades after they were written.
The Canadian Cascade Arc, also called the Canadian Cascades, is the Canadian segment of the North American Cascade Volcanic Arc. Located entirely within the Canadian province of British Columbia, it extends from the Cascade Mountains in the south to the Coast Mountains in the north. Specifically, the southern end of the Canadian Cascades begin at the Canada–United States border. However, the specific boundaries of the northern end are not precisely known and the geology in this part of the volcanic arc is poorly understood. It is widely accepted by geologists that the Canadian Cascade Arc extends through the Pacific Ranges of the Coast Mountains. However, others have expressed concern that the volcanic arc possibly extends further north into the Kitimat Ranges, another subdivision of the Coast Mountains, and even as far north as Haida Gwaii.
References
- ↑ Chris's journal entries Archived 2006-09-15 at the Wayback Machine Retrieved on 2007-08-05
- ↑ Deegan, F. M.; Troll, V. R.; Bédard, J. H.; Evenchick, C. A.; Dewing, K.; Grasby, S.; Geiger, H.; Freda, C.; Misiti, V.; Mollo, S. (2016). "The stiff upper LIP: investigating the High Arctic Large Igneous Province". Geology Today. 32 (3): 92–98. doi:10.1111/gto.12138. ISSN 1365-2451. S2CID 130366151.
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