A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than 1,000 cubic kilometers.
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 St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It lies 52 miles (83 km) northeast of Portland, Oregon, and 98 miles (158 km) south of Seattle. Mount St. Helens takes its English name from that of the British diplomat Alleyne Fitzherbert, 1st Baron St Helens, a friend of explorer George Vancouver who surveyed the area in the late 18th century. The volcano is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire.
Mount Shasta is a potentially active volcano at the southern end of the Cascade Range in Siskiyou County, California. At an elevation of 14,179 feet, it is the second-highest peak in the Cascades and the fifth-highest in the state. Mount Shasta has an estimated volume of 85 cubic miles, which makes it the most voluminous stratovolcano in the Cascade Volcanic Arc. The mountain and surrounding area are part of the Shasta–Trinity National Forest.
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high to intermediate levels of silica, with lesser amounts of less viscous mafic magma. Extensive felsic lava flows are uncommon, but have traveled as far as 15 km (9 mi).
The Ring of Fire is a tectonic belt of volcanoes and earthquakes.
Lassen Volcanic National Park is an American national park in northeastern California. The dominant feature of the park is Lassen Peak, the largest plug dome volcano in the world and the southernmost volcano in the Cascade Range. Lassen Volcanic National Park is one of the few areas in the world where all four types of volcanoes can be found: plug dome, shield, cinder cone, and stratovolcano.
The Lassen volcanic area presents a geological record of sedimentation and volcanic activity in and around Lassen Volcanic National Park in Northern California, U.S. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States. Pacific Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years. Heat and molten rock from these subducting plates has fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years, including these in the Lassen volcanic areas.
Lassen Peak, commonly referred to as Mount Lassen, is a lava dome volcano and the southernmost active volcano in the Cascade Range of the Western United States. Located in the Shasta Cascade region of Northern California, it is part of the Cascade Volcanic Arc, which stretches from southwestern British Columbia to northern California. Lassen Peak reaches an elevation of 10,457 ft (3,187 m), standing above the northern Sacramento Valley. It supports many flora and fauna among its diverse habitats, which are subject to frequent snowfall and reach high elevations.
On March 27, 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated until a major explosive eruption took place on May 18, 1980, at 8:32 am. The eruption, which had a volcanic explosivity index of 5, was the first to occur in the contiguous United States since the much smaller 1915 eruption of Lassen Peak in California. It has often been declared the most disastrous volcanic eruption in U.S. history.
Mount St. Helens National Volcanic Monument is a U.S. National Monument that includes the area around Mount St. Helens in Cowlitz and Skamania Counties, Washington. It was established on August 27, 1982, by U.S. President Ronald Reagan, following the 1980 eruption. The 110,000 acre (445 km2) National Volcanic Monument was set aside for research, recreation, and education. Inside the monument, the environment is left to respond naturally to the disturbance. It was the third national monument to be managed by the U.S. Forest Service.
David Alexander Johnston was an American United States Geological Survey (USGS) volcanologist who was killed by the 1980 eruption of Mount St. Helens in the U.S. state of Washington. A principal scientist on the USGS monitoring team, Johnston was killed in the eruption while manning an observation post six miles (10 km) away on the morning of May 18, 1980. He was the first to report the eruption, transmitting "Vancouver! Vancouver! This is it!" before he was swept away by a lateral blast; despite a thorough search, Johnston's body was never found, but state highway workers discovered remnants of his USGS trailer in 1993.
Harry Glicken was an American volcanologist. He researched Mount St. Helens in the United States before and after its 1980 eruption, and was very distraught about the death of volcanologist David A. Johnston, who was Glicken's mentor and supervisor in Spring 1980 at Mount St. Helens. Glicken was initially assigned to the USGS observation post in the weeks leading up to the eruption but was called away the night before the eruption.
The 2004–2008 volcanic activity of Mount St. Helens in Washington, United States has been documented as a continuous eruption in the form of gradual extrusion of magma. Starting in October 2004 and ceasing in January 2008, a new lava dome was built up. The new dome did not rise above the rim of the crater created by the 1980 eruption of Mount St. Helens.
La Garita Caldera is a large caldera and extinct supervolcano in the San Juan volcanic field in the San Juan Mountains around the town of Creede in southwestern Colorado, United States. It is west of La Garita, Colorado. The eruption that created the La Garita Caldera is among the largest known volcanic eruptions in Earth's history, as well as being one of the most powerful known supervolcanic events.
The Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 miles (1,100 km). The arc formed due to subduction along the Cascadia subduction zone. Although taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains, past the Fraser River which is the northward limit of the Cascade Range proper.
Several types of volcanic eruptions—during which material is expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.
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.
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.
The David A. Johnston Cascades Volcano Observatory (CVO) is a volcano observatory in the US that monitors volcanoes in the northern Cascade Range. It was established in the summer of 1980, after the eruption of Mount St. Helens. The observatory is named for United States Geological Survey (USGS) volcanologist David A. Johnston, who was swept away in the Mount St. Helens eruption on the morning of May 18, 1980. The observatory's current territory covers Oregon, Washington, and Idaho. The Cascade Range's extent includes northern California, and Cascade volcanoes in that state, such as Mount Shasta and Lassen Peak, previously fell under the CVO's jurisdiction. However, these volcanoes now fall under the jurisdiction of the California Volcano Observatory (CalVO), formed in February 2012 and based in Menlo Park, California, which monitors and researches volcanic activity throughout California and Nevada.
