The Explorer Ridge is a

mid-ocean ridge A mid-ocean ridge (MOR) is a undersea mountain range, seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading ...

, a divergent

tectonic plate Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

boundary located about west of

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest ...

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer plate, which together with the Juan de Fuca plate and the Gorda plate to its south, is what remains of the once-vast Farallon plate which has been largely subducted under the North American plate. The Explorer Ridge consists of one major segment, the Southern Explorer Ridge, and several smaller segments. It runs northward from the Sovanco fracture zone to the Queen Charlotte triple junction, a point where it meets the Queen Charlotte Fault and the northern Cascadia subduction zone.

Geology

This divergent boundary first formed about 5–7 million years ago when the northern end of the Juan de Fuca plate broke off along the Nootka Fault to form the Explorer plate. This apparently had some important ramifications for regional geologic evolution. When this change was completed, Cascade Arc volcanism from

Northern California Northern California (commonly shortened to NorCal) is a geocultural region that comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's List of counties in California, 58 counties. Northern Ca ...

to southwestern British Columbia returned and the present-day

Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington (state), Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as m ...

and

Olympic Mountains The Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus (Washington), Mount Olympus is the high ...

started to form. The

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramaf ...

is moving away from the Explorer Ridge to either side. On the eastern side the eastward moving Explorer plate is being subducted under the North American plate. The belt of

volcano A volcano is commonly defined as a vent or fissure 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. On Earth, volcanoes are most oft ...

es along the

Pacific Ranges The Pacific Ranges are the southernmost subdivision of the Coast Mountains portion of the Pacific Cordillera. Located entirely within British Columbia, British Columbia, Canada, they run northwest from the lower stretches of the Fraser River to B ...

are the direct results of this collision. The western side of the Explorer Ridge is associated with the northwest trending Pacific plate which has formed the Queen Charlotte Fault, an active

transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...

along the coast of British Columbia and southeast

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. The Explorer Ridge is also seismically active. Most seismicity recorded in this area occurred on or near the Explorer Transform Fault Zone. The relatively shallow depth of the Southern Explorer Ridge (up to 1800 m) in comparison with most other segments of the northeast Pacific spreading centers suggests that there has been considerable volcanic activity along this segment in the past 100,000 years.

Notable features along the ridge

The Explorer Ridge includes a deep

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges produced by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear ...

which runs along the axis of the ridge along nearly its entire length. This rift marks the actual boundary between adjacent tectonic plates, where

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

from the mantle reaches the seafloor, erupting as

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

and producing new crustal material for the plates. Before 2002 Explorer Ridge was the least explored of the northeast Pacific spreading centers, even though it was known to have robust hydrothermal activity and is seismically active. Along the Southern Explorer Ridge lies a large

hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...

area called Magic Mountain. It is an unusual hydrothermal site, with its off-axis location and relatively long-lived activity. The source of the hydrothermal fluid that fuels Magic Mountain probably rises along fault systems associated with a recent episode of rifting that, in turn, followed a massive outpouring of lava. These vents are forming seafloor massive sulfide deposits on the ocean floor. Many strange deep-water creatures have been found here.NOAA Ocean Explorer: Submarine Ring of Fire
Retrieved on 2008-06-10

References

{{coord, 49.6667, N, 130.3333, W, source:wikidata, display=title Underwater ridges of the Pacific Ocean Plate tectonics Mountain ranges of British Columbia Volcanism of British Columbia Coast of British Columbia Seismic zones of British Columbia Oceanography of Canada

Geology

Notable features along the ridge

See also

References