Tuzo Wilson Seamounts
Encyclopedia
The Tuzo Wilson Seamounts, also called J. Tuzo Wilson Knolls and Tuzo Wilson Knolls, are two young active submarine volcano
es off the coast of British Columbia
, Canada
, located 200 km (124 mi) northwest of Vancouver Island
and south of the Queen Charlotte Islands
. The two seamounts are members of the Kodiak-Bowie Seamount chain
, rising 500 m (1,640 ft) to 700 m (2,297 ft) above the mean level of the northeastern Pacific Ocean
and is a seismically active site southwest of the southern end of the Queen Charlotte Fault
. They are named after Canadian
geologist
John Tuzo Wilson.
and are surrounded by numerous smaller vents, with a total edifice volume of about 12 km3.
The lava
emitted in eruptions at the Tuzo Wilson Seamounts is made of basalt
, a common gray to black or dark brown extrusive volcanic rock
low in silica content (the lava is mafic
) that is usually fine-grained due to rapid cooling of lava. Glassy pillow lava
is found at the seamounts, a type of rock typically formed when basaltic lava emerges from a submarine volcanic vent
. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow.
The origin of the Tuzo Wilson Seamounts is not without controvrsy. Some geologist
s theorize that the Tuzo Wilson Seamounts are linked with a hotspot
because lava at the Tuzo Wilson Seamounts are fresh, glassy pillow basalts of recent age, as expected if these seamounts are located above or close to a hotspot south of the Queen Charlotte Islands. Others prefer rift
ing as the cause of volcanism because the seamounts are close to the Explorer spreading center
. No theory is close to airtight. Part of the controversy is due to the uncertain origin of the Kodiak-Bowie Seamount chain
. There is a 360 km (224 mi) long gap between recently (Late Pleistocene to Holocene) active Bowie
and Tuzo Wilson Seamounts, both of which have erupted alkaline basalts of similar composition. If a mantle plume
was responsible for activity at both seamounts, then it is likely that there would be evidence for alkaline volcanic activity in the area between these two seamounts.
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 off the coast of British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, located 200 km (124 mi) northwest of Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
and south of the Queen Charlotte Islands
Queen Charlotte Islands
Haida Gwaii , formerly the Queen Charlotte Islands, is an archipelago on the North Coast of British Columbia, Canada. Haida Gwaii consists of two main islands: Graham Island in the north, and Moresby Island in the south, along with approximately 150 smaller islands with a total landmass of...
. The two seamounts are members of the Kodiak-Bowie Seamount chain
Kodiak-Bowie Seamount chain
The Kodiak–Bowie Seamount chain, also called the Pratt–Welker Seamount chain, is a seamount chain in southeastern Gulf of Alaska stretching from the Aleutian Trench in the north to Bowie Seamount, the youngest volcano in the chain, which lies west of the Queen Charlotte Islands,...
, rising 500 m (1,640 ft) to 700 m (2,297 ft) above the mean level of the northeastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and is a seismically active site southwest of the southern end of the Queen Charlotte Fault
Queen Charlotte Fault
The Queen Charlotte Fault is an active transform fault, located between the North American Plate and the Pacific Plate, Canada's equivalent of the San Andreas Fault. The Queen Charlotte Fault forms a triple junction on its south with the Cascadia subduction zone and the Explorer Ridge...
. They are named after Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
John Tuzo Wilson.
Geology
The two submarine volcanoes are capped by hawaiiteHawaiite
Hawaiite is an olivine basalt with intermediate composition between alkali olivine and mugearite. It was first described at the island of Hawaii. In gemology, hawaiite is a colloquial term for Hawaii-originated peridot,which is gem-quality olivine mineral....
and are surrounded by numerous smaller vents, with a total edifice volume of about 12 km3.
The lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
emitted in eruptions at the Tuzo Wilson Seamounts is made of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
, a common gray to black or dark brown extrusive volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
low in silica content (the lava is mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
) that is usually fine-grained due to rapid cooling of lava. Glassy pillow lava
Pillow lava
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava under water, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one metre in...
is found at the seamounts, a type of rock typically formed when basaltic lava emerges from a submarine volcanic vent
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...
. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow.
The origin of the Tuzo Wilson Seamounts is not without controvrsy. Some geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
s theorize that the Tuzo Wilson Seamounts are linked with a hotspot
Hotspot (geology)
The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...
because lava at the Tuzo Wilson Seamounts are fresh, glassy pillow basalts of recent age, as expected if these seamounts are located above or close to a hotspot south of the Queen Charlotte Islands. Others prefer rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing as the cause of volcanism because the seamounts are close to the Explorer spreading center
Explorer Ridge
The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis...
. No theory is close to airtight. Part of the controversy is due to the uncertain origin of the Kodiak-Bowie Seamount chain
Kodiak-Bowie Seamount chain
The Kodiak–Bowie Seamount chain, also called the Pratt–Welker Seamount chain, is a seamount chain in southeastern Gulf of Alaska stretching from the Aleutian Trench in the north to Bowie Seamount, the youngest volcano in the chain, which lies west of the Queen Charlotte Islands,...
. There is a 360 km (224 mi) long gap between recently (Late Pleistocene to Holocene) active Bowie
Bowie Seamount
Bowie Seamount is a large submarine volcano in the northeastern Pacific Ocean, located west of Haida Gwaii, British Columbia, Canada.The seamount is named after William Bowie of the Coast & Geodetic Survey....
and Tuzo Wilson Seamounts, both of which have erupted alkaline basalts of similar composition. If a mantle plume
Mantle plume
A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...
was responsible for activity at both seamounts, then it is likely that there would be evidence for alkaline volcanic activity in the area between these two seamounts.
See also
- Volcanism of Canada
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- List of volcanoes in Canada
- Geology of the Pacific NorthwestGeology of the Pacific NorthwestThe geology of the Pacific Northwest refers to the study of the composition , structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada...