Vance Seamounts
Encyclopedia
The Vance Seamounts are a group of seven submarine volcano
es 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
.
The easternmost five of the seven were surveyed using SeaBeam bathymetry. A chemical analysis of the lavas of the volcanoes indicated that the materials erupted from the volcanoes are relatively primitive. With the exception of one, the volcanoes form a nearly linear chain of circular volcanic cones. The second volcano from the northwest is not discretely shaped like the rest, rather it is a rough structure of lava cones and flows, which cover an area of at least 25 by 10 km (15.5 by 6.2 mi). The six conical volcanoes (not including the odd one) range from 15 to 67 km³ (3.6 to 16.1 cumi) in volume, averaging 34 ±.
Most of the volcanoes have gently sloping plateau
s, in conformity with their low shield volcano
–like profiles, which have been heavily modified by multiple caldera
s. These are generally very shallow, having been formed then filled almost completely by younger flows, leaving only parts of the rims untouched. Some also have landslide debris
deposits near the base of the caldera rims, and several have since been breached (their sides have collapsed). Small cones lay along the seafloor surrounding the main formation. The southeastern volcanoes also have low-level parallel faults arranged linearly against the Juan de Fuca Ridge.
The construction of the cones left a lot of debris scattered across the ocean surface, much of which is aligned parallel to the ridge axis. The largest of these cones are nearly 2 km (1 mi) across, whereas the smallest appear to be only a few hundred meters in diameter.
In 2006, an expedition was conducted by the Monterey Bay Aquarium Research Institute
on the seamount formations.
Submarine volcano
Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...
es located west of the Juan de Fuca Ridge
Juan de Fuca Ridge
The Juan de Fuca Ridge is a tectonic spreading center located off the coasts of the state of Washington in the United States and the province of British Columbia in Canada. It runs northward from a transform boundary, the Blanco Fracture Zone, to a triple junction with the Nootka Fault and the...
. Most of the seamounts contain a caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
. They are the southernmost of several near-ridge chains located on the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
, stemming from the Juan de Fuca Ridge
Juan de Fuca Ridge
The Juan de Fuca Ridge is a tectonic spreading center located off the coasts of the state of Washington in the United States and the province of British Columbia in Canada. It runs northward from a transform boundary, the Blanco Fracture Zone, to a triple junction with the Nootka Fault and the...
.
The easternmost five of the seven were surveyed using SeaBeam bathymetry. A chemical analysis of the lavas of the volcanoes indicated that the materials erupted from the volcanoes are relatively primitive. With the exception of one, the volcanoes form a nearly linear chain of circular volcanic cones. The second volcano from the northwest is not discretely shaped like the rest, rather it is a rough structure of lava cones and flows, which cover an area of at least 25 by 10 km (15.5 by 6.2 mi). The six conical volcanoes (not including the odd one) range from 15 to 67 km³ (3.6 to 16.1 cumi) in volume, averaging 34 ±.
Most of the volcanoes have gently sloping plateau
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
s, in conformity with their low shield volcano
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
–like profiles, which have been heavily modified by multiple caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
s. These are generally very shallow, having been formed then filled almost completely by younger flows, leaving only parts of the rims untouched. Some also have landslide debris
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
deposits near the base of the caldera rims, and several have since been breached (their sides have collapsed). Small cones lay along the seafloor surrounding the main formation. The southeastern volcanoes also have low-level parallel faults arranged linearly against the Juan de Fuca Ridge.
The construction of the cones left a lot of debris scattered across the ocean surface, much of which is aligned parallel to the ridge axis. The largest of these cones are nearly 2 km (1 mi) across, whereas the smallest appear to be only a few hundred meters in diameter.
In 2006, an expedition was conducted by the Monterey Bay Aquarium Research Institute
Monterey Bay Aquarium Research Institute
The Monterey Bay Aquarium Research Institute is a not-for-profit oceanographic research center in Moss Landing, California affiliated with the Monterey Bay Aquarium. It was founded in 1987 by David Packard of Hewlett-Packard fame...
on the seamount formations.