A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface, and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to 1,000–4,000 m (3,300–13,100 ft) in height. They are defined by oceanographers as independent features that rise to at least 1,000 m (3,281 ft) above the seafloor, characteristically of conical form. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface, such flat-top seamounts are called "guyots" or "tablemounts".
A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.
An active volcano is a volcano that has erupted during the Holocene, is currently erupting, or has the potential to erupt in the future. A volcano that is not currently erupting but could erupt in the future is known as a dormant volcano. Volcanoes that will not erupt again are known as extinct volcanoes.
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 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.
Axial Seamount is a seamount, submarine volcano, and underwater shield volcano in the Pacific Ocean, located on the Juan de Fuca Ridge, approximately 480 km (298 mi) west of Cannon Beach, Oregon. Standing 1,100 m (3,609 ft) high, Axial Seamount is the youngest volcano and current eruptive center of the Cobb–Eickelberg Seamount chain. Located at the center of both a geological hotspot and a mid-ocean ridge, the seamount is geologically complex, and its origins are still poorly understood. Axial Seamount is set on a long, low-lying plateau, with two large rift zones trending 50 km (31 mi) to the northeast and southwest of its center. The volcano features an unusual rectangular caldera, and its flanks are pockmarked by fissures, vents, sheet flows, and pit craters up to 100 m (328 ft) deep; its geology is further complicated by its intersection with several smaller seamounts surrounding it.
Bowie Seamount, or SG̱aan Ḵinghlas in the Haida language, is a large submarine volcano in the northeastern Pacific Ocean, located 180 km (110 mi) west of Haida Gwaii, British Columbia, Canada. The seamount is also known as Bowie Bank. The English name for the feature is after William Bowie of the United States Coast and Geodetic Survey.
The Vance Seamounts are a group of seven submarine volcanoes located west of the Juan de Fuca Ridge. Most of the seamounts contain a caldera. They are the southernmost of several near-ridge chains located on the Pacific Plate, stemming from the Juan de Fuca Ridge.
Davidson Seamount is a seamount located off the coast of Central California, 80 mi (129 km) southwest of Monterey and 75 mi (121 km) west of San Simeon. At 26 mi (42 km) long and 8 mi (13 km) wide, it is one of the largest known seamounts in the world. From base to crest, the seamount is 7,480 ft (2,280 m) tall, yet its summit is still 4,101 ft (1,250 m) below the sea surface. The seamount is biologically diverse, with 237 species and 27 types of deep-sea coral having been identified.
Detroit Seamount, which was formed around 76 million years ago, is one of the oldest seamounts of the Hawaiian-Emperor seamount chain. It lies near the northernmost end of the chain and is south of Aleutian Islands, at 51°28.80′N167°36′E
Pioneer Seamount is an undersea mountain, or seamount, in the Pacific Ocean off the coast of central California.
Daikakuji Seamount is a seamount and the southwesternmost volcanic feature in the Hawaiian Emperor chain bend area.
Rodriguez Seamount is a seamount and guyot located in the Pacific Ocean about 150 km off the coast of Central California. It is structurally similar to the nearby Guide, Pioneer, Gumdrop, and Davidson seamounts, all located roughly between 37.5° and 34.0° degrees North latitude. This group of seamounts is morphologically unique, and the mounts are very similar to one another. The seamount structures run parallel to an ancient spreading center which has since been replaced in its role by the San Andreas Fault system.
Guide Seamount is a seamount in the eastern Pacific Ocean, about 16.6±0.5 million years old. It is similar in shape and orientation to the nearby Davidson, Pioneer, Rodriguez, and Gumdrop seamounts. It is named for the United States Coast and Geodetic Survey survey ship USC&GS Guide.
The President Jackson Seamounts are a series of seamounts located on the Pacific Plate, off of California. It consists of 8 seamounts, 4 independent and 4 morpohologically fused, just west of the northern Gorda Ridge. They are generally very small, and arranged linearly.
Monowai Seamount is a volcanic seamount to the north of New Zealand. It is formed by a large caldera and a volcanic cone just south-southeast from the caldera. The volcanic cone rises to depths of up to 100 metres (330 ft) but its depth varies with ongoing volcanic activity, including sector collapses and the growth of lava domes. The seamount and its volcanism were discovered after 1877, but only in 1980 was it named "Monowai" after a research ship of the same name.
Vailuluʻu is a volcanic seamount discovered in 1975. It rises from the sea floor to a depth of 593 m (1,946 ft) and is located between Taʻu and Rose islands at the eastern end of the Samoa hotspot chain. The basaltic seamount is considered to mark the current location of the Samoa hotspot. The summit of Vailuluʻu contains a 2 km wide, 400 m deep oval-shaped caldera. Two principal rift zones extend east and west from the summit, parallel to the trend of the Samoan hotspot. A third less prominent rift extends southeast of the summit.
Tropic Seamount is a Cretaceous seamount, part of the Canary Islands Seamount Province. It is located west of the Western Sahara's coastline and southwest of the Canary Islands, north of Cape Verde. It is one of a number of seamounts in this part of the Atlantic Ocean, probably formed by volcanic processes triggered by the proximity to the African continent. Tropic Seamount is located at a depth of 970 metres (3,180 ft) and has a summit platform with an area of 120 square kilometres (46 sq mi).
Coral Patch Seamount is a seamount between Madeira and mainland Portugal in the North Atlantic Ocean. It is an elongated 120 kilometres (75 mi) long and 70 kilometres (43 mi) wide mountain that rises to a depth of about 645 metres (2,116 ft), with nine volcanic cones on its summit. It has steeper southern slopes and a gentle northern slope. To its west lies Ampére Seamount, and together with several neighbouring seamounts it is one of the Horseshoe Seamounts.
The Minami-Hiyoshi Seamount is an active seamount in the Bonin Islands of Japan.
