in what direction was the pacific plate moving while the emperor seamounts were forming
northwesterly direction
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terminates at the Kuril–Kamchatka Trench, a subduction zone at the border of Russia. The oldest age for the Emperor Seamounts is 81 million years, and comes from Detroit Seamount. However, Meiji Guyot, located to the north of Detroit Seamount, is likely somewhat older. In 1963, geologist John Tuzo Wilson hypothesized the origins of the Hawaiian–Emperor seamount chain, explaining that they were created by a hotspot of volcanic activity that was essentially stationary as the Pacific tectonic plate drifted in a northwesterly direction, leaving a trail of increasingly eroded volcanic islands and seamounts in its wake. An otherwise inexplicable kink in
Hawaiian–Emperor seamount chain
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terminates at the Kuril–Kamchatka Trench, a subduction zone at the border of Russia. The oldest age for the Emperor Seamounts is 81 million years, and comes from Detroit Seamount. However, Meiji Guyot, located to the north of Detroit Seamount, is likely somewhat older. In 1963, geologist John Tuzo Wilson hypothesized the origins of the Hawaiian–Emperor seamount chain, explaining that they were created by a hotspot of volcanic activity that was essentially stationary as the Pacific tectonic plate drifted in a northwesterly direction, leaving a trail of increasingly eroded volcanic islands and seamounts in its wake. An otherwise inexplicable kink in
Hawaiian–Emperor seamount chain
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above a center of upwelling magma called a mantle plume. The seamounts comprising the Kodiak-Bowie Seamount chain would be formed above the mantle plume and carried away from the mantle plume's magmatic source as the Pacific Plate moves in a northwesterly direction towards the Aleutian Trench, along the southern coastline of Alaska. The volcanic rocks which make up some of the seamounts in the Kodiak-Bowie Seamount chain are unusual in that they have an acid-neutralizing chemical substance like typical ocean-island basalts but a low percentage of strontium as found at mid-ocean ridge basalts. However, the strontium-bearing volcanic rocks comprising Bowie
Bowie Seamount
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the chain marks a shift in the movement of the Pacific plate some 47 million years ago, from a northward to a more northwesterly direction, and the kink has been presented in geology texts as an example of how a tectonic plate can shift direction comparatively suddenly. A look at the USGS map on the origin of the Hawaiian Islands clearly shows this "spearpoint". In a more recent study, Sharp and Clague (2006) interpret the bend as starting at about 50 million years ago. They also conclude that the bend formed from a "traditional" cause—a change in the direction of
Hawaiian–Emperor seamount chain
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earthquakes; for example the Mariana Trench, Puerto Rico Trench, and the volcanic arc along the Great Sumatran fault. A transform-fault boundary, or simply a transform boundary is where two plates will slide past each other, and the irregular pattern of their edges may catch on each other. The lithosphere is neither added to from the asthenosphere nor is it destroyed as in convergent plate action. For example, along the San Andreas fault strike-slip fault zone, the Pacific Tectonic Plate has been moving along at about 5 cm/yr in a northwesterly direction, whereas the North American Plate is moving south-easterly. Rising
Submarine earthquake
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in the Pacific Ocean. The Pacific Plate is moving north-westward direction at a speed of ~5.5 cm per year. Periodic volcanic events have led to magma eruption onto the seafloor, forming seamounts. The last known volcanic activity was at Axial Seamount, which is currently directly overlying the hot spot. The total magamtic flux from the Cobb Hot Spot is about 0.3 cubic m/yr. Although the Cobb hotspot is currently located beneath the Juan de Fuca ridge, this has not always been the case. It went under the Juan de Fuca Ridge when the Pacific plate started moving northwest and eventually
Cobb–Eickelberg Seamount chain
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Juan de Fuca Plate to its north, is what remains of the once-vast Farallon Plate. These two oceanic plates are currently moving east, subducting underneath the North American Plate in what is known as the Cascadia Subduction Zone. To the west and south of the ridge is the Pacific Plate, which is currently moving west diverging from the Gorda Plate. The divergence of the Pacific Plate and the Gorda Plate has led to the creation of the Gorda Ridge. On the Pacific Plate, roughly 50 km west of the northern portion of the ridge, sit eight seamounts (underwater volcanoes), known
Gorda Ridge
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as the President Jackson Seamounts. Roughly 30 Mya the Farallon Plate subducted beneath the North American Plate, segmenting the Pacific Farallon Ridge. This subduction created new microplates and new ridges, including the Juan de Fuca Plate and Juan de Fuca Ridge. As the Juan de Fuca Plate continued to subduct underneath the North American Plate it also segmented, creating the Gorda Plate and Gorda Ridge. The Pacific Plate is moving in a northwest direction, creating a divergence with the Gorda Plate at a speed of 5 cm per year. The Juan de Fuca Plate (including the Gorda Plate) is moving
Gorda Ridge
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in stages from sources within the Earth's mantle to vents on the seafloor. Seamounts provide data on movements of tectonic plates on which they ride, and on the rheology of the underlying lithosphere. The trend of a seamount chain traces the direction of motion of the lithospheric plate over a more or less fixed heat source in the underlying asthenosphere part of the Earth's mantle. There are thought to be up to an estimated 50,000 seamounts in the Pacific basin. The Emperor Seamounts are an excellent example of an entire volcanic chain undergoing this process and contain many guyots among
Guyot
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occur on the seamounts. The Musicians Seamounts lie in the north-central Pacific, north of the Hawaiian Ridge north and northwest of Necker Island, extending over a length of . The seamounts were formerly known as the North Hawaiian Seamount Range and were among the first submarine mountains to be thoroughly researched. The seamounts consist of two separate chains (one trending in north-south direction parallel to the Emperor Seamounts and the other in northwest-southeast direction parallel to the northern Line Islands) of ridges that extend east-west and seamounts. Seamounts have usually an elliptical cross section and heights of and no flat
Musicians Seamounts
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118° western longitude and between 17° and 19° southern latitude. The Pukapuka submarine ridge extends west of the field towards the Tuamotu islands. The Rano Rahi seamount field consists of several chains of seamounts which emanate from the East Pacific Rise. These chains are lined up in the direction of the motion of the Pacific Plate and the farther away from the East Pacific Ridge the more the seamounts overlap with each other until they form ridges, which reach median lengths of . The seamounts in the field are typically less than wide but several kilometres wide; seamounts that are
Rano Rahi seamounts
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with dozens of seamounts, formed by the Easter hotspot. The range begins with Pukao and next Moai, two seamounts to the west of Easter Island, and extends east to the Nazca Ridge. The ridge was formed by the Nazca Plate moving over the Easter hotspot. Located about 350 km east of the East Pacific Rise, Easter Island lies within the Nazca Plate, bordering the Easter Microplate. The Nazca-Pacific relative plate movement due to the seafloor spreading, amounts to about 150 mm per year. This movement over the Easter hotspot has resulted in the Easter Seamount Chain, which merges into the
Easter Island
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of plate tectonics, the magma supply is cut, and the volcano goes dormant. Meanwhile, the process repeats all over again, this time forming a new island, on and on until the hotspot collapses. The theory was developed to explain the Hawaiian-Emperor seamount chain, where historic islands could be traced to the northwest in the direction that the Pacific Plate is moving. The early theory put these fixed sources of heat for the plumes deep within the Earth; however, recent research has led scientists to believe that hotspots are actually dynamic, and able to move on their own accord. The Galapagos
Galápagos hotspot
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Musicians Seamounts Musicians Seamounts are a chain of seamounts in the Pacific Ocean, north of the Hawaiian Ridge. There are about 65 seamounts, some of which are named after musicians. These seamounts exist in two chains, one of which has been attributed to a probably now-extinct hotspot called the Euterpe hotspot. Others may have formed in response to plate tectonics associated with the boundary between the Pacific Plate and the former Farallon Plate. The seamounts were constructed on young oceanic crust during the Cretaceous, but a second phase of volcanic activity took place during the Eocene. Deep sea coral reefs
Musicians Seamounts
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name to the field; it means "many volcanoes". Rano Rahi seamounts Rano Rahi (Rapa Nui: "Many volcanoes") is a field of seamounts in the Pacific Ocean. These seamounts in part form a series of ridges on the Pacific Plate pointing away from the neighbouring East Pacific Rise and which were volcanically active until about 230,000 years ago, and possibly even more recently. The origin of these seamounts is unclear. Proposals include the effect of tectonic forces on the Pacific Plate and the presence of mantle flow towards the East Pacific Rise. This field lies west of the East Pacific Rise,
Rano Rahi seamounts
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Rano Rahi seamounts Rano Rahi (Rapa Nui: "Many volcanoes") is a field of seamounts in the Pacific Ocean. These seamounts in part form a series of ridges on the Pacific Plate pointing away from the neighbouring East Pacific Rise and which were volcanically active until about 230,000 years ago, and possibly even more recently. The origin of these seamounts is unclear. Proposals include the effect of tectonic forces on the Pacific Plate and the presence of mantle flow towards the East Pacific Rise. This field lies west of the East Pacific Rise, and covers an area between the Rise and
Rano Rahi seamounts
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the Ngatemato seamounts deformed the Pacific plate enough with their weight to trigger the eruption of magma. Taukina seamounts Taukina seamounts are a series of seamounts on the Pacific Plate. The Macdonald hotspot and the Ngatemato seamounts are located nearby. The Taukina and Ngatemato seamounts were discovered in 1996 by the RV Maurice Ewing and both are named after families in Rapa Iti. The Taukina seamounts are formed by small volcanoes, with heights of and widths of . They often feature a caldera on their summit. Tholeiitic rocks make up the seamounts. The shape of the Taukina seamounts resembles that
Taukina seamounts
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at their site, and crustal weaknesses associated with the so-called "bending line" in the region which was formed by a change in the motion of the Pacific Plate. About 10,000 seamounts and islands are estimated to dot the floor of the Pacific Ocean, forming clusters and chains. The origin of chains of seamounts and islands is commonly explained with the hotspot hypothesis, which posits that as the crust migrates above a stationary hotspot volcanism forms these structures. A further hypothesis states that the hotspots, sourced from mantle plumes, are static with respect to each other and thus geologists can reconstruct
Musicians Seamounts
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It is unknown whether the seamount chain has been subducting under the Eurasian Plate, and whether the hotspot is older than Meiji Seamount, as any older seamounts have since been destroyed by the plate margin. It is also possible that a collision near the Aleutian Trench had changed the velocity of the Pacific Plate, explaining the hotspot chain's bend; the relationship between these features is still being investigated. The composition of the volcanoes' magma has changed significantly according to analysis of the strontium–niobium–palladium elemental ratios. The Emperor Seamounts were active for at least 46 million years, with the oldest lava
Hawaii hotspot
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of plate movements 26-11 million years ago, causing a change in the trend of local fracture zones. A microplate formed at that time and was eventually attached to the Pacific plate when the spreading zone between the Pacific Plate and the microplate became inactive. Part of the Foundation Seamounts lie on this ex-microplate, which is called the "Selkirk microplate". The passage of this microplate above the hotspot has altered its volcano-building activity, which generated more discrete seamounts while beneath the thicker microplate, and conversely the interaction between the Foundation system and plate boundaries may be responsible for the formation of
Foundation Seamounts
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Zealandia then locked together with Australia to form the Australian Plate (40 Ma), and a new plate boundary was created between the Australian Plate and Pacific Plate. Most islands in the Pacific are high islands (volcanic islands), such as, Easter Island, American Samoa and Fiji, among others, having peaks up to 1300 m rising abruptly from the shore. The Northwestern Hawaiian Islands were formed approximately 7 to 30 million years ago, as shield volcanoes over the same volcanic hotspot that formed the Emperor Seamounts to the north and the Main Hawaiian Islands to the south. Hawaii's tallest mountain Mauna Kea
Oceania
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Cobb–Eickelberg Seamount chain The Cobb-Eickelberg seamount chain is a range of undersea mountains formed by volcanic activity of the Cobb hotspot located in the Pacific Ocean. The seamount chain extends to the southeast on the Pacific Plate, beginning at the Aleutian Trench and terminating at Axial Seamount, located on the Juan de Fuca Ridge.The seamount chain is spread over a vast length of approximately 1200 km. The location of the Cobb hotspot that gives rise to these seamounts is 46° N -130° W. The Pacific plate is moving to the northwest over the hotspot, causing the seamounts in the chain
Cobb–Eickelberg Seamount chain
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a chain of guyots and seamounts on the Pacific Plate roughly parallel to the Hawaiian–Emperor seamount chain in the northern pacific. The Louisville collision zone migrates southward at a rate of because of the difference in the oblique angle between the Louisville Ridge relative the direction of convergence. In the eastern Lau Basin spreading centres are propagating southward at roughly the same rate. The collision zone also offsets the Tonga Trench to the north-west relative to the Kermadec Trench by . The subducting Louisville Ridge has caused a significant amount of erosion on the outer edge of the southern Tonga
Tonga Trench
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sometimes take place. Cobb–Eickelberg Seamount chain The Cobb-Eickelberg seamount chain is a range of undersea mountains formed by volcanic activity of the Cobb hotspot located in the Pacific Ocean. The seamount chain extends to the southeast on the Pacific Plate, beginning at the Aleutian Trench and terminating at Axial Seamount, located on the Juan de Fuca Ridge.The seamount chain is spread over a vast length of approximately 1200 km. The location of the Cobb hotspot that gives rise to these seamounts is 46° N -130° W. The Pacific plate is moving to the northwest over the hotspot, causing the seamounts
Cobb–Eickelberg Seamount chain
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hydrothermal venting and the eruption of a lava flow between 1997-2001 where the Foundation Seamounts intersect the Pacific-Antarctic Ridge. The Foundation Seamounts were discovered in 1992 through satellite altimetry observations. They are named after the National Science Foundation, a name-giving inspired to the naming of the Society Islands after the British Royal Society. Both toponyms were given in honour of the role that both groups played in science, mapping and navigation. The Foundation Seamounts are located in a part of the Pacific Plate where major tectonic events have occurred. The breakup of the Farallon Plate was accompanied by a reorganization
Foundation Seamounts
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Plate in the north, the Cocos Plate off today's Central America, and the Nazca and Phoenix Plates in the southern Pacific. Charles Darwin had proposed a theory of the slow subsidence of the ocean floor based on his studies of Pacific oceanic islands, seamounts (underwater volcanoes) and guyots (flat-topped seamounts). His observations have been verified and expanded in the development of plate tectonic theory. The tectonic plates continue to move today. The slowest ridge spreading rate is across the Gakkel Ridge in the Arctic Ocean which separates at less than 2.5 cm/yr while the fastest, across the East Pacific Rise
Geology of the Pacific Ocean
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about . The seamounts were discovered in 1996 by the RV Maurice Ewing in the Austral Islands. Potassium-argon dating yields ages of about 30 million years; the seamounts developed close to the East Pacific Rise. Away from the Austral Islands the Ngatemato seamounts merge with the Foundation seamounts, with which they may share an origin. Macdonald seamount and associated seamounts as well as the Taukina seamounts developed close to the Ngatemato seamounts, the deformation of the Pacific Plate imposed by the Ngatemato seamounts may have triggered the formation of these other two seamounts. Alternatively the Ngatemato seamounts and Macdonald may
Ngatemato seamounts
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Meiji Seamount Meiji Seamount, named after Emperor Meiji, the 122nd Emperor of Japan, is the oldest seamount in the Hawaiian-Emperor seamount chain, with an estimated age of 82 million years. It lies at the northernmost end of the chain, and is perched at the outer slope of the Kuril-Kamchatka Trench. Like the rest of the Emperor seamounts, it was formed by the Hawaii hotspot volcanism, grew to become an island, and has since subsided to below sea level, all while being carried first north and now northwest by the motion of the Pacific Plate. Meiji Seamount is thus an example
Meiji Seamount
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Taukina seamounts Taukina seamounts are a series of seamounts on the Pacific Plate. The Macdonald hotspot and the Ngatemato seamounts are located nearby. The Taukina and Ngatemato seamounts were discovered in 1996 by the RV Maurice Ewing and both are named after families in Rapa Iti. The Taukina seamounts are formed by small volcanoes, with heights of and widths of . They often feature a caldera on their summit. Tholeiitic rocks make up the seamounts. The shape of the Taukina seamounts resembles that of the seamounts that form on the East Pacific Rise. An alternate theory of origin is that
Taukina seamounts
3366327
angle of about 120°. This bend was long attributed to a relatively sudden change of 60° in the direction of plate motion, but research conducted in 2003 suggests that it was the movement of the hotspot itself that caused the bend. The issue is still currently under academic debate. All of the volcanoes in this part of the chain have long since subsided below sea level, becoming seamounts and guyots (see also the seamount and guyot stages of Hawaiian volcanism). Many of the volcanoes are named after former emperors of Japan. The seamount chain extends to the West Pacific, and
Hawaiian–Emperor seamount chain
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47 million years ago. This volcanism occurred at the time of major changes in the motion of the Pacific Plate; stresses occurring within the plate may have reactivated the Musicians volcanoes and resulted in this late stage activity. One earthquake has been recorded in the province during historical time. Musicians Seamounts Musicians Seamounts are a chain of seamounts in the Pacific Ocean, north of the Hawaiian Ridge. There are about 65 seamounts, some of which are named after musicians. These seamounts exist in two chains, one of which has been attributed to a probably now-extinct hotspot called the Euterpe hotspot.
Musicians Seamounts
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Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands. Hillis and Müller are reported to consider the Bird's Head Plate to be moving in unison with the Pacific Plate. Bird considers them to be unconnected. The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of
Pacific Plate
742234
areas, and cause hundreds of billions of dollars in damage. The Pacific Plate, to the west of the fault, is moving in a northwest direction while the North American Plate to the east is moving toward the southwest, but relatively southeast under the influence of plate tectonics. The rate of slippage averages about a year across California. The southwestward motion of the North American Plate towards the Pacific is creating compressional forces along the eastern side of the fault. The effect is expressed as the Coast Ranges. The northwest movement of the Pacific Plate is also creating significant compressional forces
San Andreas Fault
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Plate movement across a hot-spot produces a line of islands oriented in the direction of the plate movement. An example is the Hawaiian Islands, from Hawaii to Kure, which continue beneath the sea surface in a more northerly direction as the Emperor Seamounts. Another chain with similar orientation is the Tuamotu Archipelago; its older, northerly trend is the Line Islands. The southernmost chain is the Austral Islands, with its northerly trending part the atolls in the nation of Tuvalu. Tristan da Cunha is an example of a hotspot volcano in the Atlantic Ocean. Another hotspot in the Atlantic is the
Island
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seamounts made of serpentinized periodite. They are formed from mud volcanism. The composition for the seamounts differ in the Izu-Ogasawara Trench and Mariana systems which indicates regional changes in geology. The tectonic plate is approximately 100 km thick and converging to the east at a rate of 50-80 mm/yr with the Pacific Plate subducting at 60-100 mm/yr This eastern subduction is divided into the Mariana Trench, which forms the southeastern boundary, and the Izu-Ogasawara Trench the northeastern boundary. The Izu-Ogasawara Trench and Mariana subduction zones are traveling at different rates. While the northern section of the Izu-Ogasawara Trench plate is
Mariana Plate
3864619
went through the rejuvenated stage, while its younger neighbors, East Molokai and West Maui, have evidently done so. It is currently unknown what stage of development the submerged volcano of Penguin Bank is in. In recent years research at other seamounts, for instance Jasper Seamount, has confirmed that the Hawaiian model applies to other seamounts as well. Evolution of Hawaiian volcanoes The fifteen volcanoes that make up the eight principal islands of Hawaii are the youngest in a chain of more than 129 volcanoes that stretch across the North Pacific Ocean, called the Hawaiian-Emperor seamount chain. Hawaii's volcanoes rise an
Evolution of Hawaiian volcanoes
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Mid-Pacific Mountains The Mid-Pacific Mountains (MPM) is a large oceanic plateau located in the central North Pacific Ocean or south of the Hawaiian–Emperor seamount chain. Of volcanic origin and Mesozoic in age, it is located on the oldest part of the Pacific Plate and rises up to (Darwin Rise) above the surrounding ocean floor and is covered with several layers of thick sedimentary sequences that differs from those of other plateaux in the North Pacific. seamounts are distributed over the MGM. Some of the highest points in the range are above sea level which include Wake Island and Marcus Island.
Mid-Pacific Mountains
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Hotspots are sites of upwelling of relatively hot mantle, possibly associated with mantle plumes, that cause partial melting of the asthenosphere. This type of magmatism forms volcanic seamounts or oceanic islands when they become emergent. Over short geological timescales the hotspots appear to be fixed relative to one another, forming a reference frame against which plate motions can be measured. As tectonic plates move relative to a hotspot, the location of magmatic activity on the plate shifts, causing the development of time-progressive chains of volcanoes such as the Hawaiian–Emperor seamount chain. The main product of hotspot volcanoes are Ocean Island
Magmatism
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on the dates of the northwest-southeast trend and the older Line Islands are consistent with each other. It is possible that their formation was influenced by the nearby presence of a spreading ridge, a process which has been suggested for other hotspots such as Réunion, Iceland, Azores and others as well. The Farallon Plate-Pacific Plate spreading ridge was located east of the Musicians Seamounts and flow from the hotspot to the ridge may have generated the east-west trending ridges of the Musicians Seamounts. Alternative explanations for the formation of the Musicians Seamounts is the presence of a former spreading ridge
Musicians Seamounts
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a convex arrangement pointing to the Pacific Ocean, while the oceanic trenches that form the western boundary of the Pacific Plate are convex in the opposite direction, toward Eurasia. The continental crust above the subduction zones had previously been associated with the Eurasian Plate, but northern Honshu and Hokkaido have more recently been treated as part of the North American Plate, due to a poorly defined plate boundary between Eastern Siberia and Alaska and a newly forming boundary at the eastern perimeter of the Sea of Japan. This portion of the crust has been known locally as the Okhotsk Plate.
1891 Mino–Owari earthquake
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continental shelf. The Queen Charlotte triple junction is located where the Pacific Plate and North American Plate meets with the Explorer Plate. Upon breaking apart 4 million years ago, the Juan De Fuca Plate continued moving northeast at 26 mm/year (1 in/year) while the Explorer Plate's velocity changed, stalling or moving slowly north up to 20 mm/year. The Nootka Fault boundary between the Juan De Fuca Plate and the Explorer Plate has varied in length and direction since their separation. The formation of the Nookta Fault and the shearing of plate boundaries has caused a clockwise rotation, reorienting the Sovanco
Explorer Plate
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President Jackson Seamounts The President Jackson Seamounts are a series of seamounts (underwater volcanoes) located on the Pacific Plate, off of California. It consists of 8 seamounts, 4 independent and 4 morpohologically fused, just west of the northern Gorda Ridge. They are generally very small, and arranged linearly. The assembly consists of 8 seamounts arranged in a chain. The easternmost of the seamounts is located about east of the axial ridge that spawned the volcanoes, Gorda Ridge. The chain was mapped initially with SeaBeam equipment in 1985, however its incomplete coverage limited its usefulness. A GLORIA sidescan survey conducted in
President Jackson Seamounts
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continental than oceanic crust, particularly resembling northwest Australian crust. The seamounts were found to be 47 to 136 million years old, decreasing in age from east to west, and at most 25 million years younger than the crust surrounding them. Plate reconstructions based on these dates showed that the seamounts formed where West Burma separated from Australia and India, during the breakup of Gondwana, approximately 150 million years ago. The paper proposed that the seamounts are made of recycled, delaminated continental crust enriched in mantle material that was rising beneath the mid-ocean ridge forming at the time, and that this
Christmas Island Seamount Province
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Foundation Seamounts Foundation Seamounts are a series of seamounts in the southern Pacific Ocean. Discovered in 1992, these seamounts form a long chain which starts from the Pacific-Antarctic Ridge. Some of these seamounts may have once emerged from the ocean. The Foundation Seamounts were probably formed by a now-weakening mantle plume called the Foundation hotspot that is located close to the Pacific-Antarctic Ridge. It is possible that this hotspot generated additional volcanoes, such as the Ngatemato and Taukina seamounts farther west. The oldest volcanism on the Foundation Seamounts occurred 21 million years ago, while the youngest volcanism appears to be
Foundation Seamounts
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publications, including Herman Melville's "The Encantadas" of 1854. Volcanism has been continuous on the Galápagos Islands for at least 20 myr, and perhaps even longer. The mantle plume beneath the east-ward moving Nazca Plate (51 km/myr) has given rise to a 3-kilometre-thick platform under the island chain and seamounts. Besides the Galápagos Archipelago, other key tectonic features in the region include the Northern Galápagos Volcanic Province between the archipelago and the Galápagos Spreading Center (GSC) 200 km to the north at the boundary of the Nazca Plate and the Cocos Plate. This spreading center truncates into the East Pacific Rise
Galápagos Islands
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from the island of Hawaii. There are more seamounts in the Pacific Ocean than in the Atlantic, and their distribution can be described as comprising several elongate chains of seamounts superimposed on a more or less random background distribution. Seamount chains occur in all three major ocean basins, with the Pacific having the most number and most extensive seamount chains. These include the Hawaiian (Emperor), Mariana, Gilbert, Tuomotu and Austral Seamounts (and island groups) in the north Pacific and the Louisville and Sala y Gomez ridges in the southern Pacific Ocean. In the North Atlantic Ocean, the New England Seamounts
Seamount
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Ngatemato seamounts Ngatemato seamounts (Name derived from a ruling family in Rapa) are a series of seamounts in the southern Pacific Ocean. These seamounts have the shape of ridges and display calderas. The Aureka () and Make () seamounts are part of the Ngatemato track. Dredged rocks are weakly tholeiitic basalts of Oligocene age. They are about high and wide at their base. Despite being smaller in size than the Macdonald seamounts however the Ngatemato seamounts have larger volumes which is masked by stronger plate deformation; the magma output that created the Ngatemato and Taukina chains when summed up is
Ngatemato seamounts
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into the Asian oceanic trenches. The oldest member disappearing by way of the Plate Tectonics cycle is early-Cretaceous (145 to 137 million years ago). All maps of the Earth's ocean floor geology show ages younger than 145 million years, only about 1/30 of the Earth's 4.55 billion year history. Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands. Hillis and Müller are reported to consider the Bird's Head Plate to be moving in
Pacific Plate
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to all this the seamounts are pocketed by multiple small cones, and are littered by debris ranging far and wide from the range. There is evidence of erosional activity throughout, with erosional valleys and landslide debris visible. President Jackson Seamounts The President Jackson Seamounts are a series of seamounts (underwater volcanoes) located on the Pacific Plate, off of California. It consists of 8 seamounts, 4 independent and 4 morpohologically fused, just west of the northern Gorda Ridge. They are generally very small, and arranged linearly. The assembly consists of 8 seamounts arranged in a chain. The easternmost of the seamounts
President Jackson Seamounts
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Vance Seamounts The Vance Seamounts are a group of seven submarine volcanoes 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
Vance Seamounts
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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 over from the Aleutian Trench in the far northwest Pacific to the Loʻihi
Hawaiian–Emperor seamount chain
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ridge now found on the Nazca Plate off Northern Chile. The Pacific-Antarctic Ridge is unusually shallow ( depth instead of ) at the point where the Foundations seamounts intersect the ridge; this thickening of the ridge also alters the chemistry of erupted magmas there, leading to the occurrence of andesite and dacite which are formed within the thickened crust. This area of silicic volcanism extends southward from the point where the Pacific-Antarctic Ridge intersects the Foundation Seamounts. There is no indication of volcanism on the other side of the ridge. The Foundation Seamounts appear to originate from a hotspot, with
Foundation Seamounts
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Osbourn Seamount The Osbourn Seamount is a seamount in the south-west Pacific Ocean. It is the western-most and oldest unsubducted seamount of the Louisville Ridge, with an estimated age of 78.8 ± 1.3 . Like other seamounts comprising the Louisville Ridge, it was formed by the Louisville hotspot which is currently located away near the Pacific-Antarctic Ridge. Osbourn Seamount will eventually be destroyed by subduction in the Tonga and Kermadec trenches once it is carried into the trenches by the ongoing plate motion. The trench-chain collision zone is moving southward at a rate of / because of the oblique angle
Osbourn Seamount
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clockwise bend in the Louisville chain near Osbourn is similar to the Detroit-Meiji bend in the Hawaii–Emperor chain. Osbourn Seamount The Osbourn Seamount is a seamount in the south-west Pacific Ocean. It is the western-most and oldest unsubducted seamount of the Louisville Ridge, with an estimated age of 78.8 ± 1.3 . Like other seamounts comprising the Louisville Ridge, it was formed by the Louisville hotspot which is currently located away near the Pacific-Antarctic Ridge. Osbourn Seamount will eventually be destroyed by subduction in the Tonga and Kermadec trenches once it is carried into the trenches by the ongoing plate
Osbourn Seamount
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of Cancer, making them the only islands in Hawaii that lie outside the tropics. The Northwestern or Leeward Hawaiian Islands include: The Northwestern Hawaiian Islands were formed, approximately 7 to 30 million years ago, as shield volcanoes over the same volcanic hotspot that formed the Emperor Seamounts to the north and the Main Hawaiian Islands to the south. As the Pacific Plate moved north and later northwest over the hot spot, volcanic eruptions built up islands in a linear chain. The isolated land masses gradually eroded and subsided, evolving from high islands in the south, much like the Main Islands
Northwestern Hawaiian Islands
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Gulf of Mexico to Argentina, and off western and southern Africa. In the Indo-Pacific, it has been reported from off Okinawa and Australia, as well as on the Emperor and Hancock Seamounts in the central North Pacific and over the Nazca Plate off Peru. It is partially pelagic and occurs at depths of in open water, and from to over near the bottom. Like many other lantern sharks, adults are found deeper than juveniles. Growing to a length of at least , the blurred lanternshark has a slender body, large head, and short tail. The snout is wedge-shaped and slightly
Blurred lanternshark
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in the same direction the Plate is moving. In the classic hotspot model, primarily based on studies of the Hawaii hotspot, the volcanic islands and seamounts further away from the Samoa hotspot should be progressively older. However, Savai'i, the most western of the Samoa island chain, and Ta'u Island, the most eastern of the Samoa islands, both erupted in the last century, data which is an enigma for scientists. Another discrepancy in the data from the Samoa islands is that subaerial rock samples from Savai'i, the most western of the islands, were too young by several million years to fit
Samoan Islands
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change in absolute direction of the Pacific plate (marked by the end of the bend in the Hawaiian-Emperor seamount chain), and a change in the convergence of the Kula plate with the North American plate. As subduction waned so did the force that had clamped Siletzia against the continent, and the tectonic regime shifted from compressional to extensional. Deposition of sand from the then proximal Idaho Batholith into the Tyee Formation in southern Oregon may have continued as late as 46.5 Ma, but was interrupted when Siletzia rifted from the continent and began rotating away. What initiated rifting is unknown.
Siletzia
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it is most likely to run, and maintains a tourist site for viewing the lava. After the subaerial phase the volcano enters a series of postshield stages involving subsidence and erosion, becoming an atoll and eventually a seamount. Once the Pacific Plate moves it out of the tropics, the reef mostly dies away, and the extinct volcano becomes one of an estimated 10,000 barren seamounts worldwide. Every Emperor seamount is a dead volcano. Hawaii hotspot The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the most well-known and heavily
Hawaii hotspot
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Koko Guyot Koko Guyot (also sometimes known as "Kinmei" and Koko Seamount) is a 48.1-million-year-old guyot, a type of underwater volcano with a flat top, which lies near the southern end of the Emperor seamounts, about north of the "bend" in the volcanic Hawaiian-Emperor seamount chain. Pillow lava has been sampled on the north west flank of Koko Seamount, and the oldest dated lava is 40 million years old. Seismic studies indicate that it is built on a thick portion of the Pacific Plate. The oldest rock from the north side of Koko Seamount is dated at 52.6 and the
Koko Guyot
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motivated in part by technical problems in the drilling equipment. The Pacific Ocean seafloor is characterized by a striking contrast between the relatively flat floor of the Eastern Pacific and the Western Pacific whose seafloor is dotted by oceanic plateaus and seamounts. These structures may have formed on top of large Cretaceous uplift episodes, moving hotspots, mid-ocean ridges and transform faults. Ita Mai Tai is considered to be part of the Magellan Seamounts, a chain of seamounts that extends northwest away from this seamount, and one of their best studied members. The activity of the Magellan Seamounts has been attributed
Ita Mai Tai
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east by the Izu-Bonin and Mariana trenches, to the west by the Line Islands. Two major plateaux, the Shatsky Rise to the north and the Ontong Java Plateau to the south, border the Darwin Rise. How these plateaux relate to the rise remains disputed. There are six major chains of seamounts on the rise — the Japanese, Magellan, Wake, Marshall Islands, Line Islands seamounts and the Mid-Pacific Mountains — and numerous minor clusters. The ages of these seamounts in general follow the motion of the Pacific Plate from 130 to 180 , as predicted by conventional hotspot theory, and decrease
Darwin Rise
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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 the Queen Charlotte Islands 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. Seamounts are volcanic mountains which rise from the seafloor. The unlimited supply of water surrounding these volcanoes can cause them to behave differently from volcanoes
Bowie Seamount
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twice the average size of seamounts. Nearly 50% of guyot area and 42% of the number of guyots occur in the North Pacific Ocean, covering . The largest three guyots are all in the North Pacific: the Kuko Guyot (estimated ), Suiko Guyot (estimated ) and the Pallada Guyot (estimated ). Seamounts are often found in groupings or submerged archipelagos, a classic example being the Emperor Seamounts, an extension of the Hawaiian Islands. Formed millions of years ago by volcanism, they have since subsided far below sea level. This long chain of islands and seamounts extends thousands of kilometers northwest
Seamount
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little more than 5 million years. The "assembly line" that forms the volcanoes is driven by a hotspot, a plume of magma deep within the Earth producing lava at the surface. As the Pacific Plate moves in a west-northwest direction, each volcano moves with it away from its place of origin above the hotspot. The age and location of the volcanoes are a record of the direction, rate of movement, and orientation of the Pacific Plate. The pronounced 43-million-year-old break separating the Hawaiian Ridge from the Emperor Chain marks a dramatic change in direction of plate movement. Initial, deeper-water volcanic
Evolution of Hawaiian volcanoes
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can be used to once again predict the next eruption. The ridge is a medium rate spreading center, moving outwards at a rate of approximately 6 centimeters per year. Tectonic activity along the ridge is monitored primarily with the U.S. Navy's Sound Surveillance System (SOSUS) array of hydrophones, allowing for real time detection of earthquakes and eruptive events. The Juan de Fuca Plate is being pushed east underneath the North American Plate, forming what is known as the Cascadia subduction zone off the coast of the Pacific Northwest. The plate does not subduct smoothly and can become 'locked' with the
Juan de Fuca Ridge
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Pacific-Antarctic Ridge The Pacific-Antarctic Ridge (PAR) is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean, separating the Pacific Plate from the Antarctic Plate. It is regarded as the southern section of the East Pacific Rise in some usages, generally south of the Challenger Fracture Zone and stretching to the Macquarie Triple Junction south of New Zealand. Stretching for 4,300 km north-west from the Pacific-Antarctic Ridge to the Osbourn Seamount at Tonga and Kermadec Junction is a long line of seamounts called the Louisville Ridge - the longest such chain in the Pacific - thought
Pacific-Antarctic Ridge
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plate tectonics separated North America from Europe and North Africa and pushed it westward did the continent acquire, bit by bit, what became the Pacific Northwest. Over many millions of years, the continent collided with and incorporated islands, reefs, and other exotic terranes. Part of the last major exotic terrane acquired by the North American Plate during the Eocene lies under the Tryon Creek watershed. The terrane consisted of a chain of seamounts that by 34 million years ago was being uplifted to become the Oregon Coast Range and the Tualatin Mountains (West Hills). The easternmost exposure of the basalts
Tryon Creek
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Plate which is now mostly subducted under the North American Plate. The North American Plate itself is moving slowly in a generally southwest direction, sliding over the smaller plates as well as the huge oceanic Pacific Plate (which is moving in a northwest direction) in other locations such as the San Andreas Fault in central and southern California. Tectonic processes active in the Cascadia subduction zone region include accretion, subduction, deep earthquakes, and active volcanism of the Cascades. This volcanism has included such notable eruptions as Mount Mazama (Crater Lake) about 7,500 years ago, the Mount Meager massif (Bridge River
Cascadia subduction zone
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Linear chains of volcanoes in the Pacific have been attributed to deep mantle plumes, but a number of such chains appear to correspond to short lasting volcanism, such as processes triggered by tension in the Pacific Plate. The South Pacific Superswell is a large structure in the southern Pacific Ocean, where there are many volcanoes and the seafloor is unusually shallow. Asthenospheric processes may be responsible for its existence. The Tarava seamounts consist of eighteen separate edifices which extend across six longitudes and four latitudes over a length of , away from the Society Islands. Aside from five large guyots
Tarava seamounts
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away from the hotspot the resulting thinned lithosphere subsided forming a trough. As evidence, Van Arsdale and Cox cite the seismic zones centered on New Madrid, Missouri and Charleston, South Carolina, and the volcanic kimberlite pipes in Arkansas. Other papers argue that the lack of a chain of age-progressive seamounts (as in the Hawaiian-Emperor seamount chain), the absence of present-day volcanism, and the elongation of the Bermuda Rise oblique to plate motion are evidence against a hotspot origin for the Bermuda Rise. Peter R. Vogt and Woo-Yeol Jung alternatively attribute the Bermuda Rise to a reorganization of mantle convection associated
Bermuda hotspot
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from plate edges. Galápagos Microplate The Galapagos Microplate (GMP) is a geological feature of the oceanic crust located at 1°50' N, offshore of the west coast of Colombia. The GMP is collocated with the Galapagos Triple Junction, which is an atypical ridge-ridge-ridge triple junction. At the Galapagos Triple Junction, the Pacific Plate, Cocos Plate, and Nazca Plate meet incompletely, forming two counter-rotating microplates at the junction of the Cocos-Nazca, Pacific-Cocos, and Pacific-Nazca spreading ridges. The entire Galapagos Microplate, which covers an area of 13,000 km, was formed to accommodate the motions of three major moving plates. Before the formation of
Galápagos Microplate
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each sample; this should also signify original cooling at the same latitude as the current location of the Hawaiian hotspot. Instead of remaining constant, the paleolatitudes of the Emperor Seamounts show a change from north to south, with decreasing age. The paleomagnetic data from the seamounts of the Emperor chain suggest motion of the Hawaiian hotspot in Earth's mantle. Tarduno et al. (2009) have summarized evidence that the bend in the seamount chain may be caused by circulation patterns in the flowing solid mantle (mantle "wind") rather than a change in plate motion. The chain has been produced by the
Hawaiian–Emperor seamount chain
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contain no granite. Millions of years ago, vents and fissures opened under the Pacific Ocean and lava flowed forth, creating huge underwater mountains and ranges called seamounts. The Farallon tectonic plate that formed a part of the Pacific Ocean floor (separate from the Pacific plate) inched eastward toward North America about 35 million years ago and most of the sea floor subducted beneath the continental land mass of the North America plate. Some of the sea floor, however, was scraped off and jammed against the mainland, creating the dome that was the forerunner of today's Olympics. In this particular case,
Olympic Mountains
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subduction of the Farallon Plate. About 55 million years ago, the Kula Plate began an even more northerly motion. Riding on the Kula Plate was the Pacific Rim Terrane consisting of volcanic and sedimentary rocks. It was scraped off and plastered against the continental margin, forming what is today Vancouver Island. By 40 million years ago, the compressional force of the Kula Plate ceased. The existence of the Kula Plate was inferred from the westward bend in the alternating pattern of magnetic anomalies in the Pacific Plate. Kula Plate The Kula Plate was an oceanic tectonic plate under the northern
Kula Plate
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Galápagos Microplate The Galapagos Microplate (GMP) is a geological feature of the oceanic crust located at 1°50' N, offshore of the west coast of Colombia. The GMP is collocated with the Galapagos Triple Junction, which is an atypical ridge-ridge-ridge triple junction. At the Galapagos Triple Junction, the Pacific Plate, Cocos Plate, and Nazca Plate meet incompletely, forming two counter-rotating microplates at the junction of the Cocos-Nazca, Pacific-Cocos, and Pacific-Nazca spreading ridges. The entire Galapagos Microplate, which covers an area of 13,000 km, was formed to accommodate the motions of three major moving plates. Before the formation of the Galapagos Microplate,
Galápagos Microplate
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carried along to the northwest by the motion of the Pacific Plate, it will move into waters too cool for coral and coralline algae growth to keep up with isostatic subsidence of the mountain, so long as global warming does not interfere. Currently the atoll is warmed by the pools of water at the ends of the warm Kuroshio Current, keeping it in very comfortable range in winter. Barring unforeseen evolution, it will then begin to join the other volcanic and reef-topped remnants of the Hawaiian–Emperor seamount chain to the northwest, all of which are now seamounts. In the Hawaiian
Kure Atoll
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such superstructures as Hawaii island and the ancient Maui Nui), the oldest of the Emperor seamounts are spaced as far as apart. Tectonic plates generally focus deformation and volcanism at plate boundaries. However, the Hawaii hotspot is more than from the nearest plate boundary; while studying it in 1963, Canadian geophysicist J. Tuzo Wilson proposed the hotspot theory to explain these zones of volcanism so far from regular conditions, a theory that has since come into wide acceptance. Wilson proposed that mantle convection produces small, hot buoyant upwellings under the Earth's surface; these thermally active mantle plumes supply magma which
Hawaii hotspot
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motion of the Pacific plate. However, recent research shows that the hotspot itself may have moved with time. Some evidence comes from analysis of the orientation of the ancient magnetic field preserved by magnetite in ancient lava flows sampled at four seamounts (Tarduno "et al.", 2003): this evidence from paleomagnetism shows a more complex history than the commonly accepted view of a stationary hotspot. If the hotspot had remained above a fixed mantle plume during the past 80 million years, the latitude as recorded by the orientation of the ancient magnetic field preserved by magnetite (paleolatitude) should be constant for
Hawaiian–Emperor seamount chain
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chain, in the Gulf of Alaska, and is 33 million years of age, among the oldest in the group. The part of the chain that Patton Seamount lies in is known variably as either the "Gulf of Alaska Seamounts" or the "Patton Seamounts." The Gulf seamounts are the best-known and most heavily studied features in the chain. Patton itself is over tall and wide at is base, and originally formed off the coast of Washington 33 million years ago. It has since been moved to its present Gulf location by the northwestern movement of the Pacific Plate. Dives indicate that
Patton Seamount
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that there is a discontinuity in the chain which would have formed about 43 million years ago at the time of a major change in the motion of the Pacific Plate. The hotspot in question may be the Foundation hotspot, the Pitcairn hotspot or a now extinct third hotspot. Alternatively, the formation of the Tuamotu Plateau may have induced tectonic stress that propagated towards the location of the future Tarava seamounts. Several new species have been discovered on the Tarava seamounts, such as the "Lophiodes iwamotoi" anglerfish, the cone snail "Profundiconus tarava", the majoid crab "Samadinia longispina" and pectinoid "Parvamussium
Tarava seamounts
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of argon-argon dating, but at Discovery Seamount it may have continued until 7-6.5 million years ago. The age of the seamounts decreases in southwest direction, similar to the Walvis Ridge, and at a similar rate. Unlike the Walvis Ridge, which is connected to the Etendeka flood basalts, the Discovery Seamounts do not link with onshore volcanic features. However, it has been proposed that the 70-80 million years old Blue Hills, Gibeon and Gross Brukkaros kimberlite fields in southern Namibia may have been formed by the Discovery hotspot, and some plate reconstructions place it underneath the Karoo-Ferrar large igneous province at
Discovery Seamounts
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Tasmantid Seamount Chain The Tasmantid Seamount Chain is a long chain of seamounts in the South Pacific Ocean. The chain consists of over 16 extinct volcanic peaks, many rising more than from the seabed. It is one of the two parallel seamount chains alongside the East Coast of Australia; the Lord Howe and Tasmantid seamount chains both run north-south through parts of the Coral Sea and Tasman Sea. These chains have longitudes of approximately 159°E and 156°E respectively. Like its neighbour, the Tasmantid Seamount Chain has resulted from the Indo-Australian Plate moving northward over a stationary hotspot. It ranges in
Tasmantid Seamount Chain
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Arabian Plate is moving away from the African Plate. The New England hotspot in the Atlantic Ocean has probably created a short line of mid- to late-Tertiary age seamounts on the African Plate but appears to be currently inactive. African Plate The African Plate is a major tectonic plate straddling the equator as well as the prime meridian. It includes much of the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges. Between and , the Somali Plate began rifting from the African Plate along the East African Rift. Since the
African Plate
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volcano which rises from the seafloor of the western Pacific Ocean. A possible model for the formation of the volcanic Samoa island chain is explained by the Samoa hotspot situated at the east end of the Samoa Islands. In theory, the Samoa hotspot is a result of the Pacific Tectonic Plate moving over a 'fixed' deep and narrow mantle plume spewing up through the Earth's crust. The Samoa islands generally lie in a straight line, east to west, in the same direction the Plate is moving. In the classic hotspot model, primarily based on studies of the Hawaii hotspot, the
Savai'i
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Cook Strait. Through most of the South Island, the plates slide past each other (Alpine Fault), with slight obduction of the Pacific Plate over the Australian Plate, forming Southern Alps. From Fiordland south, the Australian Plate subducts under the Pacific Plate forming the Puysegur Trench. This configuration has lead to volcanism and extension in the North Island forming the Taupo Volcanic Zone and uplift in the South Island forming the Southern Alps. The Pacific Plate is colliding with the Australian Plate at a rate of about 40 mm/yr. The East coast of the North Island is being compressed and lifted
Geology of New Zealand
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Tarava seamounts The Tarava seamounts are a group of seamounts in the southern Pacific Ocean, southwest of the Society Islands. They are formed by five guyots and a number of cone-shaped seamounts. Of Eocene-Oligocene age, they may have formed under the influence of a hotspot. The Tarava seamounts are also known as the Savannah seamounts. East of the Tarava seamounts lie the Va'a Tau Piti seamounts, which were sometimes considered part of the Tarava seamounts but are considered geologically separate owing to their different configuration (east-west rather than northwest-southeast), which may reflect an origin close to the East Pacific Rise.
Tarava seamounts
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in high avalanche danger. The Olympic Mountains are made up of obducted clastic wedge material and oceanic crust. They are primarily Eocene sandstones, turbidites, and basaltic oceanic crust. Unlike the Cascades, the Olympic Mountains are not volcanic, and contain no granite. Millions of years ago, vents and fissures opened under the Pacific Ocean and lava flowed forth, creating huge underwater mountains and ranges called seamounts. The Farallon tectonic plate that formed a part of the Pacific Ocean floor (separate from the Pacific plate) inched eastward toward North America about 35 million years ago and most of the sea floor subducted
Steeple Rock (Washington)
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collision boundary with the North Bismarck Plate. In the south-west, the Pacific Plate has a complex but generally convergent boundary with the Indo-Australian Plate, subducting under it north of New Zealand forming the Tonga Trench and the Kermadec Trench. The Alpine Fault marks a transform boundary between the two plates, and further south the Indo-Australian Plate subducts under the Pacific Plate forming the Puysegur Trench. The southern part of Zealandia, which is to the east of this boundary, is the plate's largest block of continental crust. The northern side is a convergent boundary subducting under the North American Plate forming
Pacific Plate
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Pitcairn hotspot The Pitcairn hotspot is a volcanic hotspot located in the south-central Pacific Ocean. Over the past 11 million years, it has formed the Pitcairn-Gambier hotspot chain. It is responsible for creating the Pitcairn Islands and two large seamounts named Adams and Bounty, as well as atolls at Moruroa, Fangataufa and the Gambier Islands. The hotspot is currently located at Adams and Bounty, which are ~60 kilometers East-Southeast of Pitcairn Island. The current hotspot location is west of the spreading center known as the East Pacific Rise; an area near where the Nazca plate and the Pacific plate are
Pitcairn hotspot
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moving in a general north-northeast direction, but the Arabian Plate is moving faster, resulting in the observed left lateral motions along the fault of approximately 107 km. A component of extension is also present in the southern part of the transform, which has contributed to a series of depressions, or pull-apart basins, forming the Gulf of Aqaba, Dead Sea, Sea of Galilee and Hula basins. The DST fault system is generally considered to be a transform fault that has accommodated a 105 km northwards displacement of the Arabian Plate. This interpretation is based on observation of offset markers, such as
Dead Sea Transform
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playing out over several million years. To the extent that the accretion of Siletzia to North America can be given a definite date most studies give it as about 50 Ma. This date has added significance as it is also the start of a change in direction of the Pacific plate, as seen in the bend in the Hawaiian-Emperor seamount chain, and also a change in the Pacific Northwest from compressional to extensional tectonics. This may also be when the last of the Resurrection plate was subducted under British Columbia. Initiation of the north-striking right-lateral Straight Creek Fault at ~48
Siletzia
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could be a connection between the Foundation chain and these chains, an impression bolstered by their dates and their strike direction. The absence of seamounts between the Ngatemato and Foundation chains might reflect discontinuous volcanism. The President Thiers Bank close to Raivavae may also be linked to the Foundation hotspot, and the 135 million years old Magellan Rise may be an oceanic plateau formed by the Foundation hotspot and thus its oldest volcano. Before 25 million yars ago the hotspot might have been located below the Farallon Plate. There, it could have given rise to the Iquique Ridge, a submarine
Foundation Seamounts
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the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the Cocos Plate. The south-eastern side is a divergent boundary with the Nazca Plate forming the East Pacific Rise. The southern side is a divergent boundary with the Antarctic Plate forming the Pacific-Antarctic Ridge. The western side, the plate is bounded by the Okhotsk Plate at the Kuril-Kamchatka Trench and the Japan Trench, forms a convergent boundary by subducting under the Philippine Sea Plate creating the Mariana Trench, has a transform boundary with the Caroline Plate, and has a
Pacific Plate
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presence of Cretaceous reefs on many of them was noticed. About 6% of the Pacific seafloor is covered with almost one million seamounts. While there are some differences to present-day reef systems, many of these seamounts were formerly atolls, which today still exist. All these structures originally formed as volcanoes in the Mesozoic ocean. Fringing reefs may have developed on the volcanoes, which then became barrier reefs as the volcano subsided and turned into an atoll, and which surround a lagoon or tidal flat. The crust underneath these seamounts tends to subside as it cools, and thus the islands and
Horizon Guyot
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moving to the east relative to South America at a rate of 58 mm per year. North of the Carnegie Ridge, the subduction interface has four recognisable segments, from south to north, the Esmeraldas, Manglares, Tumaco and Patia segments. This plate boundary has been the location of several great historical earthquakes, most associated with damaging tsunamis. In 1906 a 5–600 km long segment of the plate interface ruptured, causing a M 8.8 earthquake (rupturing all four segments) and a trans-Pacific tsunami. This event was the last of three earthquakes that ruptured adjacent parts of the plate interface, forming a northeastward
1979 Tumaco earthquake
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Seamount, makes it difficult to find the exact eruptive centers. The volcano is clearly isolated, even in comparison to other seamounts in the spread-out Emperor chain, with Ojin Seamount about to the northwest and Kimmei Seamount to the southeast. The seamount is located just 2.3 degrees north of the bend. Much of what we know about Koko comes from early dredgings and the Ocean Drilling Program's core samples, collected as part of Leg 197, at Site 1206, which aimed to supply information on the relatively obscure Emperor seamounts and study their relation to the Hawaiian chain. Site 1206 was the
Koko Guyot
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zones, causing the lighter material to rise as magma, forming volcanoes. Also, material can be accreted horizontally when volcanic island arcs, seamounts or similar structures collide with the side of the continent as a result of plate tectonic movements. Continental crust is also lost through erosion and sediment subduction, tectonic erosion of forearcs, delamination, and deep subduction of continental crust in collision zones. Many theories of crustal growth are controversial, including rates of crustal growth and recycling, whether the lower crust is recycled differently from the upper crust, and over how much of Earth history plate tectonics has operated and
Continental crust
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lithosphere heated from below; as the plate moves the volcano is moved away from the heat source and volcanic activity ceases, producing a chain of volcanoes that get progressively older away from the currently active one. The "South Pacific Superswell" is a region in the Southern Pacific at the present-day Austral Islands, Cook Islands and Society Islands where intense volcanic activity was underway during the Cretaceous, and is the place where the Cretaceous seamounts of the Mid-Pacific Mountains originated. The Easter hotspot, Marquesas hotspot and the Society hotspot may have been involved in the formation of the Mid-Pacific Mountains. After
Allison Guyot
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vesiculosum". Other species found there are "Propeamussium watsoni" together with five other pectinoids, and tonnoidean gastropods. Tarava seamounts The Tarava seamounts are a group of seamounts in the southern Pacific Ocean, southwest of the Society Islands. They are formed by five guyots and a number of cone-shaped seamounts. Of Eocene-Oligocene age, they may have formed under the influence of a hotspot. The Tarava seamounts are also known as the Savannah seamounts. East of the Tarava seamounts lie the Va'a Tau Piti seamounts, which were sometimes considered part of the Tarava seamounts but are considered geologically separate owing to their different
Tarava seamounts
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Ioah and Pallada guyot north-northwest, other seamounts in the area east of Ioah are Changpogo, Gramberg, Zatonskii and Arirang. There are about 1000 seamounts in the central western Pacific. Ioah Guyot is a shield volcano with an arcuate shape; the two halves that make it up have dimensions of and . The guyot rises from the seafloor to – depth, forming a summit plateau with a surface area of that is covered by high hills. The rim of the summit plateau is formed by volcanic rocks on the eastern part of the seamount and by reefal limestones on the western.
Ioah Guyot