Grímsvötn is an active volcano with a fissure system located in Vatnajökull National Park, Iceland. The volcano itself is completely subglacial and located under the northwestern side of the Vatnajökull ice cap. The subglacial caldera is at 64°25′N17°20′W, at an elevation of 1,725 m (5,659 ft). Beneath the caldera is the magma chamber of the Grímsvötn volcano.
A jökulhlaup is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland, which are triggered by geothermal heating and occasionally by a volcanic subglacial eruption, but it is now used to describe any large and abrupt release of water from a subglacial or proglacial lake/reservoir.
The Garibaldi Volcanic Belt is a northwest–southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in southwestern British Columbia, Canada. It forms the northernmost segment of the Cascade Volcanic Arc, which includes Mount St. Helens and Mount Baker. Most volcanoes of the Garibaldi chain are dormant stratovolcanoes and subglacial volcanoes that have been eroded by glacial ice. Less common volcanic landforms include cinder cones, volcanic plugs, lava domes and calderas. These diverse formations were created by different styles of volcanic activity, including Peléan and Plinian eruptions.
Hyaloclastite is a volcanoclastic accumulation or breccia consisting of glass fragments (clasts) formed by quench fragmentation of lava flow surfaces during submarine or subglacial extrusion. It occurs as thin margins on the lava flow surfaces and between pillow lavas as well as in thicker deposits, more commonly associated with explosive, volatile-rich eruptions as well as steeper topography. Hyaloclastites form during volcanic eruptions under water, under ice or where subaerial flows reach the sea or other bodies of water. It commonly has the appearance of angular flat fragments sized between a millimeter to few centimeters. The fragmentation occurs by the force of the volcanic explosion, or by thermal shock and spallation during rapid cooling.
A tuya is a flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are rare worldwide, being confined to regions which were covered by glaciers and had active volcanism during the same period.
Hoodoo Mountain, sometimes referred to as Hoodoo Volcano, is a potentially active stratovolcano in the Northern Interior of British Columbia, Canada. It is located 25 kilometres northeast of the Alaska–British Columbia border on the north side of the Iskut River opposite of the mouth of the Craig River. With a summit elevation of 1,850 metres and a topographic prominence of 900 metres, Hoodoo Mountain is one of many prominent peaks within the Boundary Ranges of the Coast Mountains. Its flat-topped summit is covered by an ice cap more than 100 metres thick and at least 3 kilometres in diameter. Two valley glaciers surrounding the northwestern and northeastern sides of the mountain have retreated significantly over the last hundred years. They both originate from a large icefield to the north and are the sources of two meltwater streams. These streams flow along the western and eastern sides of the volcano before draining into the Iskut River.
Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volcanic areas, including Iceland, Alaska, and parts of the Andes. Jökulhlaups have been identified as the most frequently occurring volcanic hazard in Iceland, with major events where peak discharges of meltwater can reach 10,000 – 100,000 m3/s occurring when there are large eruptions beneath glaciers.
Several types of volcanic eruptions—during which lava, tephra, and assorted gases are 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.
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.
Brown Bluff is a basalt tuya on the Tabarin Peninsula of northern Antarctica. It formed in the last 1 million years as a result of subglacial eruptions within an englacial lake. The volcano's original diameter is thought to have been about 12–15 kilometers (7.5–9.3 mi) and was probably formed by a single vent. Brown Bluff is divided into four stages: pillow volcano, tuff cone, slope failure, and hyaloclastite delta; and into five structural units.
A subglacial mound (SUGM) is a type of subglacial volcano. This type of volcano forms when lava erupts beneath a thick glacier or ice sheet. The magma forming these volcanoes was not hot enough to melt a vertical pipe right through the overlying glacial ice, instead forming hyaloclastite and pillow lava deep beneath the glacial ice field. Once the glaciers had retreated, the subglacial volcano would be revealed, with a unique shape as a result of their confinement within glacial ice. They are somewhat rare worldwide, being confined to regions which were formerly covered by continental ice sheets and also had active volcanism during the same period. They are found throughout Iceland, Antarctica and the Canadian province of British Columbia.
The volcanic history of the Northern Cordilleran Volcanic Province presents a record of volcanic activity in northwestern British Columbia, central Yukon and the U.S. state of easternmost Alaska. The volcanic activity lies in the northern part of the Western Cordillera of the Pacific Northwest region of North America. Extensional cracking of the North American Plate in this part of North America has existed for millions of years. Continuation of this continental rifting has fed scores of volcanoes throughout the Northern Cordilleran Volcanic Province over at least the past 20 million years and occasionally continued into geologically recent times.
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.
Glaciovolcanism is volcanism and related phenomena associated with glacial ice. The ice commonly constrains the erupted material and melts to create meltwater. Considerable melting of glacial ice can create massive lahars and glacial outburst floods known as jökulhlaups.
The Mount Cayley volcanic field (MCVF) is a remote volcanic zone on the South Coast of British Columbia, Canada, stretching 31 km (19 mi) from the Pemberton Icefield to the Squamish River. It forms a segment of the Garibaldi Volcanic Belt, the Canadian portion of the Cascade Volcanic Arc, which extends from Northern California to southwestern British Columbia. Most of the MCVF volcanoes were formed during periods of volcanism under sheets of glacial ice throughout the last glacial period. These subglacial eruptions formed steep, flat-topped volcanoes and subglacial lava domes, most of which have been entirely exposed by deglaciation. However, at least two volcanoes predate the last glacial period and both are highly eroded. The field gets its name from Mount Cayley, a volcanic peak located at the southern end of the Powder Mountain Icefield. This icefield covers much of the central portion of the volcanic field and is one of the several glacial fields in the Pacific Ranges of the Coast Mountains.
Azas Plateau is a volcanic field in Russia. It is also known as East Tuva Plateau, Khamsara-Biykhem Plateau and Northeast Tuva Plateau. It covers a surface area of 2,000 square kilometres (770 sq mi) west of Lake Baikal. Volcanic activity in the area also occurred at the Oka Plateau and the Jom-Bolok volcanic field.
Sveifluháls is a mafic hyaloclastite ridge of 397 m height in the southwest of Iceland in Gullbringusýsla. It is part of Krýsuvík volcanic system and of the protected area Reykjanes Fólkvangur.
Gjálp is a hyaloclastite ridge (tindar) in Iceland under the Vatnajökull glacier shield. It originated in an eruption series in 1996 and is probably part of the Grímsvötn volcanic system, though not all the scientists involved are of this opinion.
Ice cauldrons are ice formations within glaciers that cover some subglacial volcanoes. They can have circular to oblong forms. Their surface areas reach from some meters to up to 1 or more kilometers.
