Kodiak-Bowie Seamount chain
Encyclopedia
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 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 coral
s, 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.
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
chain in southeastern Gulf of Alaska
Gulf of Alaska
The Gulf of Alaska is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, where Glacier Bay and the Inside Passage are found.The entire shoreline of the Gulf is...
stretching from the Aleutian Trench
Aleutian Trench
The Aleutian Trench is a subduction zone and oceanic trench which runs along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. It is classified as a "marginal trench" in the east as it runs along the margin of the continent, and...
in the north to Bowie Seamount
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....
, the youngest volcano in the chain, which lies 180 km (112 mi) west 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...
, 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...
. The oldest volcano in the chain is the Kodiak Seamount
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...
. 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
Bowie hotspot
The Bowie hotspot is a volcanic hotspot, located 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...
. 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
Patton Seamount
Patton Seamount is a prominent seamount in the Cobb-Eickelberg Seamount chain in the Gulf of Alaska. Located east of Kodiak Island and reaching to within of the ocean surface, Patton is one of the largest seamounts in the Cobb-Eickelberg Seamount chain...
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 coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s, sponges, and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
. 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
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....
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
Marine Protected Area
Marine Protected Areas, like any protected area, are regions in which human activity has been placed under some restrictions in the interest of conserving the natural environment, it's surrounding waters and the occupant ecosystems, and any cultural or historical resources that may require...
on December 8, 1998.
The Kodiak–Bowie seamount chain is at the northern triple junction
Triple junction
A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction a boundary will be one of 3 types - a ridge, trench or transform fault - and triple junctions can be described according to the types of plate margin that meet at them...
between the Pacific
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....
, North American
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
, and Juan de Fuca
Juan de Fuca Plate
The Juan de Fuca Plate, named after the explorer of the same name, is a tectonic plate, generated from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone...
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.
Volcanoes
Volcanoes in the chain include:- Kodiak SeamountKodiak SeamountKodiak 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...
(24 m.y. old) - Giacomini Seamount (21 m.y. old)
- Pratt Seamount (age unknown)
- Welker Seamount (15 m.y. old)
- Dickens Seamount (~4 m.y. old)
- Denson SeamountDenson SeamountDenson 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...
(18 .m.y. old) - Durgin Seamount
- Brown Seamount
- Quinn Seamount
- Surveyor Seamount
- Peirce SeamountPeirce SeamountPeirce Seamount, also called Pierce Seamount, is a seamount located in the Pacific Ocean west of the Queen Charlotte Islands, British Columbia, Canada...
- Hodgkins SeamountHodgkins SeamountHodgkins Seamount is a seamount in the Kodiak-Bowie Seamount chain, located south of Pierce Seamount and north of Bowie Seamount. Hodgkins Seamount has apparently experienced two generically different episodes of volcanism, separated by about 12 million years ago...
- Bowie SeamountBowie SeamountBowie 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....
(>0.7 m.y. old) - Tuzo Wilson SeamountsTuzo Wilson SeamountsThe 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 northwest of Vancouver Island and south of the Queen Charlotte Islands...