The Kodiak–Bowie Seamount chain, also called the Pratt–Welker Seamount chain and the Kodiak Seamounts, 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 180 km (112 mi) west of the Queen Charlotte Islands, British Columbia, Canada. The oldest volcano in the chain is the Kodiak Seamount. Although the Kodiak Seamount is the oldest extant seamount in the Kodiak-Bowie chain, the adjacent lower slope contains transverse scars indicating earlier subduction of seamounts.
The Kodiak–Bowie Seamount chain are mostly extinct volcanoes that formed above the Bowie hotspot. This is a 100-to-150-km-wide morphological swell presumably of thickened hotspot generated crust, although there are no seismic refraction data across the swell to define crustal thickness. The crest of one such peak, Patton Seamount originally formed off Washington state as a submerged volcano 33 million years ago. Over time, as the Pacific Plate moved steadily northwest, Patton Seamount was carried off the Bowie hotspot and into the Gulf of Alaska. New volcanoes were formed one after another over the hotspot, creating the Kodiak–Bowie Seamount chain.
Explorations of the Kodiak–Bowie Seamount chain have shown that despite the fact that most of the seamounts were created by the Bowie hotspot, all are unique in their size, shape, and volcanic features. The seamounts teem with deep-sea corals, sponges, and fish. Recent expeditions to these seamounts using manned submersibles and ROVs have discovered many marine species and have greatly expanded the knowledge of the range of deep sea corals in this region. For example, the Bowie Seamount is a biologically rich area with a dynamic and productive ecosystem. Because of this unique biological rich area, Bowie Seamount was declared a Pilot Marine Protected Area on December 8, 1998.
The Kodiak–Bowie seamount chain is at the northern triple junction between the Pacific, North American, and Juan de Fuca plates. Available age determinations on Kodiak and Giacomini Seamounts give an approximate average rate of movement along the chain of 6.5 cm (3 in) per year.
|Kodiak–Bowie Seamount chain|
Map of the Kodiak-Bowie Seamount chain
|Location||North Pacific Ocean|
Volcanoes in the chain include:
Bowie Seamount 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. In the Russian language, Bowie is called Гора Бауи (Gora Baui), which literally means Mount Bowie. In Haida language it is called SG̱aan Ḵinghlas, meaning Supernatural One Looking Outward. It is named after William Bowie of the U.S. Coast and Geodetic Survey.The volcano has a flat-topped summit rising about 3,000 m (10,000 ft) above the seabed, to 24 m (79 ft) below sea level. The seamount lies at the southern end of a long underwater volcanic mountain range called the Pratt-Welker or Kodiak-Bowie Seamount chain, stretching from the Aleutian Trench in the north almost to Haida Gwaii in the south.Bowie Seamount lies on the Pacific Plate, a large segment of the Earth's surface which moves in a northwestern direction under the Pacific Ocean. It is adjacent to two other submarine volcanoes; Hodgkins Seamount on its northern flank and Graham Seamount on its eastern flank.Bowie hotspot
The Bowie hotspot is a volcanic hotspot, located 180 kilometres (110 mi) west of the Queen Charlotte Islands in the Pacific Ocean.
Almost all magma created by the hotspot has the composition of basalt, and so the volcanoes are constructed almost entirely of this igneous rock. The eruptions from the Bowie hotspot are effusive eruptions because basaltic magma is relatively fluid compared with magmas typically involved in more explosive eruptions, such as the andesitic magmas that produce some of the spectacular and dangerous eruptions around the margins of the Pacific Ocean.
Bowie hotspot is believed to be perhaps 100 to 150 km (60 to 90 mi) wide and underlain by a mantle plume that is relatively deep. It is also considerably weak.Eruptions from the Bowie hotspot have left a trail of underwater mountains across the Pacific, called the Kodiak-Bowie Seamount chain, which is an underwater mountain region of seamounts along a line beneath the northern Pacific Ocean. The oldest volcano in the chain is Kodiak Seamount with an estimated age of 24 million years and the youngest called Bowie Seamount.
Geological studies show that the base of Bowie Seamount formed less than a million years ago. The summit of Bowie Seamount is even younger and shows signs of having been active as recently as 18,000 years ago. Because of its shallow depth, some geologists believe Bowie Seamount was an active volcanic island throughout last ice age.Denson Seamount
Denson Seamount is a submarine volcano in the Kodiak-Bowie Seamount chain, with an estimated age of 18 million years. It lies at the southern end of the chain near the Canada–United States border. It was one of the underground volcanic extrusions investigated by the 2004 Gulf of Alaska Seamount Expedition. The expedition's goal was:
"Our goal was to gain an understanding of the geologic histories of the five previously unexplored seamounts in the Gulf of Alaska. To achieve this we created a full-coverage swath bathymetry map of each seamount and its surroundings, and we collected rock samples at all possible depths." -Randy Keller, Oregon State University
On August 6, 2004, the DSV Alvin dropped down near the Denson Seamount and collected basaltic rock to try to determine the age of the seamount. The search was difficult because the salty water had altered the volcanic rock over time, but they determined in lab tests that the Denson Seamount was about 18 million years old. The team used bathymetric mapping to render three-dimensional images of the Denson Seamount and its counterparts.Geology of the Pacific Northwest
The geology of the Pacific Northwest includes the composition (including rock, minerals, and soils), structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada. 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.
The geology of the Pacific Northwest is vast and complex. Most of the region began forming about 200 million years ago as the North American Plate started to drift westward during the rifting of Pangaea. Since that date, the western edge of North America has grown westward as a succession of island arcs and assorted ocean-floor rocks have been added along the continental margin.
There are at least five geologic provinces in the area: the Cascade Volcanoes, the Columbia Plateau, the North Cascades, the Coast Mountains, and the Insular Mountains. The Cascade Volcanoes are an active volcanic region along the western side of the Pacific Northwest. The Columbia Plateau is a region of subdued geography that is inland of the Cascade Volcanoes, and the North Cascades are a mountainous region in the northwest corner of the United States, extending into British Columbia. The Coast Mountains and Insular Mountains are a strip of mountains along the coast of British Columbia, each with its own geological history.Guyot
In marine geology, a guyot (pronounced ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than 200 m (660 ft) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi). Guyots are most commonly found in the Pacific Ocean, but they have been identified in all the oceans except the Arctic Ocean.Hawaiian–Emperor seamount chain
The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean. The seamount chain, containing over 80 identified undersea volcanoes, stretches about 6,200 kilometres (3,900 mi) from the Aleutian Trench in the far northwest Pacific to the Loʻihi seamount, the youngest volcano in the chain, which lies about 35 kilometres (22 mi) southeast of the Island of Hawaiʻi.Hodgkins Seamount
Hodgkins Seamount is a seamount in the Kodiak-Bowie Seamount chain, located south of Pierce Seamount and north of Bowie Seamount. It has apparently experienced two generically different episodes of volcanism, separated by about 12 million years. Like the rest of the Kodiak-Bowie seamounts, it was formed by the Bowie hotspot.Hotspot (geology)
In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.Kodiak Seamount
Kodiak Seamount is the oldest seamount in the Kodiak-Bowie Seamount chain, with an estimated age of 24 million years. It lies at the northernmost end of the chain and its flat-topped summit is strewn with fault lines. Like the rest of the Kodiak-Bowie seamounts, it was formed by the Bowie hotspot.
Kodiak Seamount will eventually be destroyed by subduction by the Aleutian Trench once it is carried into the trench by the ongoing plate motion, although this will not fully occur for several million more years if the current rate of motion is maintained. Because of Kodiak Seamount's approach into the Aleutian Trench, it is literally cracking up under the stress. Although Kodiak is the oldest extant seamount in the Kodiak-Bowie chain, the adjacent lower slope contains transverse scars indicating earlier subduction of seamounts.Olympic-Wallowa Lineament
The Olympic-Wallowa lineament (OWL) – first reported by cartographer Erwin Raisz in 1945 on a relief map of the continental United States – is a physiographic feature of unknown origin in the state of Washington (northwestern U.S.) running approximately from the town of Port Angeles, on the Olympic Peninsula to the Wallowa Mountains of eastern Oregon.Outline of oceanography
The following outline is provided as an overview of and introduction to Oceanography.Peirce Seamount
Peirce Seamount, also called Pierce Seamount, is a seamount located in the Pacific Ocean west of the Queen Charlotte Islands, British Columbia, Canada. It lies between Denson Seamount and Hodgkins Seamount and is member of the Kodiak-Bowie Seamount chain, a chain of seamounts in southeastern Gulf of Alaska stretching from the Aleutian Trench in the north to Bowie Seamount in the south.Tuzo Wilson Seamounts
The Tuzo Wilson Seamounts, also called J. Tuzo Wilson Knolls and Tuzo Wilson Knolls, are two young active submarine volcanoes off the coast of British Columbia, Canada, located 200 km (124 mi) northwest of Vancouver Island and south of the Haida Gwaii archipelago (briefly known as 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.