The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaiʻi in the south to northernmost Kure Atoll. The group was known to Europeans and Americans as the Sandwich Islands, a name chosen by James Cook in honor of the First Lord of the Admiralty John Montagu, 4th Earl of Sandwich; the contemporary name is derived from the name of Hawaii Island. The U. S. state of Hawaii now occupies the archipelago in its entirety, with the sole exception of Midway Island, which instead separately belongs to the United States as one of its unincorporated territories within the United States Minor Outlying Islands. The Hawaiian Islands are the exposed peaks of a great undersea mountain range known as the Hawaiian–Emperor seamount chain, formed by volcanic activity over a hotspot in the Earth's mantle; the islands are about 1,860 miles from the nearest continent. Captain James Cook visited the islands on January 18, 1778, named them the "Sandwich Islands" in honor of John Montagu, 4th Earl of Sandwich, one of his sponsors as the First Lord of the Admiralty.
This name was in use until the 1840s, when the local name "Hawaii" began to take precedence. The Hawaiian Islands have a total land area of 6,423.4 square miles. Except for Midway, an unincorporated territory of the United States, these islands and islets are administered as Hawaii—the 50th state of the United States; the eight main islands of Hawaii are listed here. All except Kahoolawe are inhabited. Smaller islands and reefs form the Northwestern Hawaiian Islands, or Hawaiian Leeward Islands: Nihoa Necker French Frigate Shoals Gardner Pinnacles Maro Reef Laysan Lisianski Island Pearl and Hermes Atoll Midway Atoll Kure Atoll The state of Hawaii counts 137 "islands" in the Hawaiian chain; this number includes all minor islands and islets, or small islands, offshore of the main islands and individual islets in each atoll. These are just a few: Ford Island Lehua Ka'ula Kaohikaipu Mānana Mōkōlea Rock Nā Mokulua Molokini Mokoliʻi Moku Manu Moku Ola Moku o Loʻe Sand Island Grass Island This chain of islands, or archipelago, developed as the Pacific Plate moved northwestward over a hotspot in the Earth's mantle at a rate of 32 miles per million years.
Thus, the southeast island is volcanically active, whereas the islands on the northwest end of the archipelago are older and smaller, due to longer exposure to erosion. The age of the archipelago has been estimated using potassium-argon dating methods. From this study and others, it is estimated that the northwesternmost island, Kure Atoll, is the oldest at 28 million years; the only active volcanism in the last 200 years has been on the southeastern island, Hawaiʻi, on the submerged but growing volcano to the extreme southeast, Loʻihi. The Hawaiian Volcano Observatory of the USGS documents recent volcanic activity and provides images and interpretations of the volcanism. Kīlauea has been erupting nearly continuously since 1983. All of the magma of the hotspot has the composition of basalt, so the Hawaiian volcanoes are composed entirely of this igneous rock. There is little coarser-grained gabbro and diabase. Nephelinite is exposed on the islands but is rare; the majority of eruptions in Hawaiʻi are Hawaiian-type eruptions because basaltic magma is fluid compared with magmas 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 basin.
Hawaiʻi island is the youngest island in the chain, built from five volcanoes. Mauna Loa, taking up over half of the Big Island, is the largest shield volcano on the Earth; the measurement from sea level to summit is more than 2.5 miles, from sea level to sea floor about 3.1 miles.. The Hawaiian Islands have many earthquakes caused by volcanic activity. Most of the early earthquake monitoring took place in Hilo, by missionaries Titus Coan, Sarah J. Lyman and her family. From 1833 to 1896 4 or 5 earthquakes were reported per year. Hawaii accounted for 7.3% of the United States' reported earthquakes with a magnitude 3.5 or greater from 1974 to 2003, with a total 1533 earthquakes. Hawaii ranked as the state with the third most earthquakes over this time period, after Alaska and California. On October 15, 2006, there was an earthquake with a magnitude of 6.7 off the northwest coast of the island of Hawaii, near the Kona area of the big island. The initial earthquake was followed five minutes by a magnitude 5.7 aftershock.
Minor-to-moderate damage was reported on most of the Big Island. Several major roadways became impassable from rock slides, effects were felt as far away as Honolulu, nearly 150 miles from the epicenter. Power outages lasted for several hours to days. Several water mains ruptured. No deaths or life-threatening injuries were reported. On May 4, 2018 there was a 6.9 earthquake in the zone of volcanic activity from Kīlauea. Earthquakes are monitored by the Hawaiian Volcano Observatory run by the USGS; the Hawaiian Islands are subjec
Zealandia known as the New Zealand continent or Tasmantis, is an entirely submerged mass of continental crust that sank after breaking away from Australia 60–85 million years ago, having separated from Antarctica between 85 and 130 million years ago. It has variously been described as a continental fragment, a microcontinent, a submerged continent, a continent; the name and concept for Zealandia was proposed by Bruce Luyendyk in 1995. Zealandia's status as a continent is not universally accepted, but New Zealand geologist Nick Mortimer has commented that "if it wasn't for the ocean" it would have been recognized as such long ago; the land mass may have been submerged about 23 million years ago, most of it remains submerged beneath the Pacific Ocean. With a total area of 4,920,000 km2, it is the world's largest current microcontinent, more than twice the size of the next-largest microcontinent and more than half the size of the Australian continent; as such, due to other geological considerations, such as crustal thickness and density, it is arguably a continent in its own right.
This was the argument which made news in 2017, when geologists from New Zealand, New Caledonia, Australia concluded that Zealandia fulfills all the requirements to be considered a continent, rather than a microcontinent or continental fragment. Zealandia supports substantial inshore fisheries and contains gas fields, of which the largest known is New Zealand's Maui gas field, near Taranaki. Permits for oil exploration in the Great South Basin were issued in 2007. Offshore mineral resources include iron sands, volcanic massive sulfides and ferromanganese nodule deposits. Zealandia is made up of two nearly parallel ridges, separated by a failed rift, where the rift breakup of the continent stops and becomes a filled graben; the ridges rise above the sea floor to heights of 1,000–1,500 m, with few rocky islands rising above sea level. The ridges are continental rock, but are lower in elevation than normal continents because their crust is thinner than usual 20 km thick, they do not float as high above the Earth's mantle.
About 25 million years ago, the southern part of Zealandia began to shift relative to the northern part. The resulting displacement by 500 km along the Alpine Fault is evident in geological maps. Movement along this plate boundary has offset the New Caledonia Basin from its previous continuation through the Bounty Trough. Compression across the boundary has uplifted the Southern Alps, although due to rapid erosion their height reflects only a small fraction of the uplift. Farther north, subduction of the Pacific Plate has led to extensive volcanism, including the Coromandel and Taupo Volcanic Zones. Associated rifting and subsidence has produced the Hauraki Graben and more the Whakatane Graben and Wanganui Basin. Volcanism on Zealandia has taken place in various parts of the continental fragment before and after it rifted away from the supercontinent Gondwana. Although Zealandia has shifted 6,000 km to the northwest with respect to the underlying mantle from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits magma composition similar to that of volcanoes in adjacent parts of Antarctica and Australia.
This volcanism is widespread across Zealandia but of low volume apart from the huge mid to late Miocene shield volcanoes that developed the Banks and Otago Peninsulas. In addition, it took place continually in numerous limited regions all through the Late Cretaceous and the Cenozoic. However, its causes are still in dispute. During the Miocene, the northern section of Zealandia might have slid over a stationary hotspot, forming the Lord Howe Seamount Chain. Zealandia is divided by scientists into two regions, North Zealandia and South Zealandia, the latter of which contains most of the Median Batholith crust; these two features are separated by the Alpine Fault and Kermadec Trench and by the wedge-shaped Hikurangi Plateau, are moving separately to each other. The case for Zealandia being a continent in its own right was argued by Nick Mortimer and Hamish Campbell in their book Zealandia: Our continent revealed in 2014, citing geological and ecological evidence to support the proposal. In 2017, a team of eleven geologists from New Zealand, New Caledonia, Australia concluded that Zealandia fulfills all the requirements to be considered a drowned continent, rather than a microcontinent or continental fragment.
This was covered by news media. New Caledonia lies at the northern end of the ancient continent, while New Zealand rises at the plate boundary that bisects it; these land masses are two outposts including Araucarias and Podocarps. At Curio Bay, logs of a fossilized forest related to modern Kauri and Norfolk Pine can be seen that grew on Zealandia about 180 million years ago during the Jurassic period, before it split from Gondwana; these were buried by volcanic mud flows and replaced by silica to produce the fossils now exposed by the sea. During glacial periods, more of Zealandia becomes a terrestrial rather than a marine environment. Zealandia was thought to have no native land mammal fauna, but the discovery in 2006 of a fossil mammal jaw from the Miocene in the Otago region shows otherwise; the total land area of Zealandia is 286,655 km2. Of this, New Zealand comprises the majority, at 267,988 km2 which includes the mainland, nearby islands, most ou
The Pacific Ocean is the largest and deepest of Earth's oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west and the Americas in the east. At 165,250,000 square kilometers in area, this largest division of the World Ocean—and, in turn, the hydrosphere—covers about 46% of Earth's water surface and about one-third of its total surface area, making it larger than all of Earth's land area combined; the centers of both the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean. The equator subdivides it into the North Pacific Ocean and South Pacific Ocean, with two exceptions: the Galápagos and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific, its mean depth is 4,000 meters. The Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 meters; the western Pacific has many peripheral seas. Though the peoples of Asia and Oceania have traveled the Pacific Ocean since prehistoric times, the eastern Pacific was first sighted by Europeans in the early 16th century when Spanish explorer Vasco Núñez de Balboa crossed the Isthmus of Panama in 1513 and discovered the great "southern sea" which he named Mar del Sur.
The ocean's current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favorable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means "peaceful sea". Important human migrations occurred in the Pacific in prehistoric times. About 3000 BC, the Austronesian peoples on the island of Taiwan mastered the art of long-distance canoe travel and spread themselves and their languages south to the Philippines and maritime Southeast Asia. Long-distance trade developed all along the coast from Mozambique to Japan. Trade, therefore knowledge, extended to the Indonesian islands but not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of this trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality. From 1404 to 1433 Zheng He led expeditions into the Indian Ocean; the first contact of European navigators with the western edge of the Pacific Ocean was made by the Portuguese expeditions of António de Abreu and Francisco Serrão, via the Lesser Sunda Islands, to the Maluku Islands, in 1512, with Jorge Álvares's expedition to southern China in 1513, both ordered by Afonso de Albuquerque from Malacca.
The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and reached a new ocean. He named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. In 1519, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Spanish expedition to the Spice Islands that would result in the first world circumnavigation. Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters; the ocean was called the Sea of Magellan in his honor until the eighteenth century. Although Magellan himself died in the Philippines in 1521, Spanish Basque navigator Juan Sebastián Elcano led the remains of the expedition back to Spain across the Indian Ocean and round the Cape of Good Hope, completing the first world circumnavigation in a single expedition in 1522. Sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, Papua New Guinea.
In 1542–43 the Portuguese reached Japan. In 1564, five Spanish ships carrying 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi, sailed to the Philippines and Mariana Islands. For the remainder of the 16th century, Spanish influence was paramount, with ships sailing from Mexico and Peru across the Pacific Ocean to the Philippines via Guam, establishing the Spanish East Indies; the Manila galleons operated for two and a half centuries, linking Manila and Acapulco, in one of the longest trade routes in history. Spanish expeditions discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, the Admiralty Islands in the South Pacific. In the quest for Terra Australis, Spanish explorations in the 17th century, such as the expedition led by the Portuguese navigator Pedro Fernandes de Queirós, discovered the Pitcairn and Vanuatu archipelagos, sailed the Torres Strait between Australia and New Guinea, named after navigator Luís Vaz de Torres. Dutch explorers, sailing around southern Africa engaged in discovery and trade.
In the 16th and 17th centuries Spain considered the Pacific Ocean a mare clausum—a sea closed to other naval powers. As the only known entrance from the Atlantic, the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western side of the Pacific Ocean the Dutch threatened the Spanish Philippines; the 18th cen
The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada and is subducted under the North American Plate. Along with the Juan De Fuca Plate and Gorda Plate, the Explorer Plate is a remnant of the ancient Farallon Plate, subducted under the North American Plate; the Explorer Plate separated from the Juan De Fuca Plate 4 million years ago. In its smoother, southern half, the average depth of the Explorer plate is 2,400 metres and rises up in its northern half to a variable basin between 1,400 metres and 2,200 metres in depth; the eastern boundary of the Explorer Plate is being subducted under the North American Plate. The southern boundary is a collection of transform faults, the Sovanco Fracture Zone, separating the Explorer Plate from the Pacific Plate. To the southeast is another transform boundary, the Nootka Fault, which separates the Explorer Plate from the Juan de Fuca Plate and forms a triple junction with the North American Plate.
To the northwest is a divergent boundary with the Pacific Plate forming the Explorer Ridge, the Winona Basin located within the northwest boundaries and the Pacific 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 while the Explorer Plate's velocity changed, stalling or moving 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 Fracture Zone northwards along the North American Plate and slowing the Explorer Plate’s subduction; the Sovanco Fracture Zone originated as a spreading center offset more than 7 million years ago which show southward movement from the influence of the Explorer ridge and results in uneven spreading eastward unto the Explorer Plate.
The subducted portion of the plate extends downward to more than 300 km depth, laterally as far as mainland Canada. The relative buoyancy of the subducting plate and the underlying mantle may be inhibiting the Explorer Plate’s ability to descend further into the mantle. There is an ongoing debate regarding the process of subduction of the Explorer Plate and how the boundary between the Explorer plate and the North American Plate are defined: The Explorer Plate has stopped and may accrete, fusing with the North American plate as the subduction has stopped and will become a plate boundary between the North American Plate and Pacific Plate rather than continuing its subduction; the Explorer Plate consists of two parts with half being fused to the North American Plate and the other half remaining a microplate system. The Explorer Plate has slowed to a terminal speed of 20 mm/year, will continue until the entire plate is subducted; as a part of the Pacific Ring of Fire, the Explorer Plate has a high level of seismic activity.
However, the activity consists of low-magnitude events. The Explorer Plate is the most seismically active area of Canada, but is anomalous as a subduction zone since most of the seismic activity occurs around the plate's perimeter rather than at the subduction interface. Events are centered around the southern and north-western areas where the borders of the plate are in contact with other plates, however the newer ocean crust created at Explorer ridge and Juan de Fuca ridge reduces the rigidity of the region and contributes to the low-magnitude of events in the region. Geology of the Pacific Northwest Cascadia tectonic history
In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents produce rifts which become rift valleys. Most active divergent plate boundaries exist as mid-oceanic ridges. Divergent boundaries form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill. Current research indicates that complex convection within the Earth's mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary; this supplies the area with vast amounts of heat and a reduction in pressure that melts rock from the asthenosphere beneath the rift area forming large flood basalt or lava flows. Each eruption occurs in only a part of the plate boundary at any one time, but when it does occur, it fills in the opening gap as the two opposing plates move away from each other. Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary.
Because of this, rocks closest to a boundary are younger than rocks further away on the same plate. At divergent boundaries, two plates move away from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below; the origin of new divergent boundaries at triple junctions is sometimes thought to be associated with the phenomenon known as hotspots. Here, exceedingly large convective cells bring large quantities of hot asthenospheric material near the surface and the kinetic energy is thought to be sufficient to break apart the lithosphere; the hot spot which may have initiated the Mid-Atlantic Ridge system underlies Iceland, widening at a rate of a few centimeters per year. Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and the East Pacific Rise, in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley. Divergent boundaries can create massive fault zones in the oceanic ridge system.
Spreading is not uniform, so where spreading rates of adjacent ridge blocks are different, massive transform faults occur. These are many bearing names, that are a major source of submarine earthquakes. A sea floor map will show a rather strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis. If one views the sea floor between the fracture zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear. Crest depths of the old ridges, parallel to the current spreading center, will be older and deeper.... It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found. Airborne geomagnetic surveys showed a strange pattern of symmetrical magnetic reversals on opposite sides of ridge centers; the pattern was far too regular to be coincidental as the widths of the opposing bands were too matched. Scientists had been studying polar reversals and the link was made by Lawrence W. Morley, Frederick John Vine and Drummond Hoyle Matthews in the Morley–Vine–Matthews hypothesis.
The magnetic banding directly corresponds with the Earth's polar reversals. This was confirmed by measuring the ages of the rocks within each band; the banding furnishes a map in space of both spreading rate and polar reversals. Mid-Atlantic Ridge Red Sea Rift Baikal Rift Zone East African Rift East Pacific Rise Gakkel Ridge Galapagos Rise Explorer Ridge Juan de Fuca Ridge Pacific-Antarctic Ridge West Antarctic Rift Great Rift Valley Convergent boundary Transform boundary Seafloor spreading – A process at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and gradually moves away from the ridge Continental drift – The movement of the Earth's continents relative to each other Subduction zone – A geological process at convergent tectonic plate boundaries where one plate moves under the other
The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about 241 km west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer Plate, which together with the Juan de Fuca Plate and the Gorda Plate to its south, is what remains of the once-vast Farallon Plate, subducted under the North American Plate; the Explorer Ridge consists of one major segment, the Southern Explorer Ridge, several smaller segments. It runs northward from the Sovanco Fracture Zone to the Queen Charlotte Triple Junction, a point where it meets the Queen Charlotte Fault and the northern Cascadia subduction zone; this divergent boundary first formed about 5-7 million years ago when the northern end of the Juan de Fuca Plate broke off along the Nootka Fault to form the Explorer Plate. This had some important ramifications for regional geologic evolution; when this change was completed, Cascade Arc volcanism from Northern California to southwestern British Columbia returned and the present-day Cascade Range and Olympic Mountains started to form.
The oceanic crust is moving away from the Explorer Ridge to either side. On the eastern side the eastward moving Explorer Plate is being subducted under the North American Plate; the belt of volcanoes along the Pacific Ranges are the direct results of this collision. The western side of the Explorer Ridge is associated with the northwest trending Pacific Plate which has formed the Queen Charlotte Fault, an active transform fault along the coast of British Columbia and southeast Alaska; the Explorer Ridge is seismically active. Most seismicity recorded in this area occurred near the Explorer Transform Fault Zone; the shallow depth of the Southern Explorer Ridge in comparison with most other segments of the northeast Pacific spreading centers suggests that there has been considerable volcanic activity along this segment in the past 100,000 years. The Explorer Ridge includes a deep rift valley which runs along the axis of the ridge along nearly its entire length; this rift marks the actual boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava and producing new crustal material for the plates.
Before 2002 Explorer Ridge was the least explored of the northeast Pacific spreading centers though it was known to have robust hydrothermal activity and is seismically active. Along the Southern Explorer Ridge lies, it is an unusual hydrothermal site, with its off-axis location and long-lived activity. The source of the hydrothermal fluid that fuels Magic Mountain rises along fault systems associated with a recent episode of rifting that, in turn, followed a massive outpouring of lava; these vents are forming seafloor massive sulfide deposits on the ocean floor. Many strange deep-water creatures have been found here. Geology of the Pacific Northwest Gorda Ridge Juan de Fuca Ridge Sovanco Fracture Zone Volcanism in Canada
A transform fault or transform boundary is a plate boundary where the motion is predominantly horizontal. It is connected to another transform, a spreading ridge, or a subduction zone. Most of these faults are hidden in the deep ocean, where they offset divergent boundaries in short zigzags resulting from seafloor spreading, the best-known being those on land at the margins of continental tectonic plates. A transform fault is the only type of strike-slip fault, classified as a plate boundary; these faults are known as conservative plate boundaries, since they neither create nor destroy lithosphere. Geophysicist and geologist John Tuzo Wilson recognized that the offsets of oceanic ridges by faults do not follow the classical pattern of an offset fence or geological marker in Reid's rebound theory of faulting, from which the sense of slip is derived; the new class of faults, called transform faults, produce slip in the opposite direction from what one would surmise from the standard interpretation of an offset geological feature.
Slip along transform faults does not increase the distance between the ridges it separates. This hypothesis was confirmed in a study of the fault plane solutions that showed the slip on transform faults points in the opposite direction than classical interpretation would suggest. Transform faults are related to transcurrent faults and are confused. Both types of fault are side-to-side in movement. In addition, transform faults have equal deformation across the entire fault line, while transcurrent faults have greater displacement in the middle of the fault zone and less on the margins. Transform faults can form a tectonic plate boundary, while transcurrent faults cannot; the effect of a fault is to relieve strain, which can be caused by compression, extension, or lateral stress in the rock layers at the surface or deep in the Earth's subsurface. Transform faults relieve strain by transporting the strain between ridges or subduction zones, they act as the plane of weakness, which may result in splitting in rift zones.
Transform faults are found linking segments of mid-oceanic ridges or spreading centres. These mid-oceanic ridges are where new seafloor is created through the upwelling of new basaltic magma. With new seafloor being pushed and pulled out, the older seafloor slides away from the mid-oceanic ridges toward the continents. Although separated only by tens of kilometers, this separation between segments of the ridges causes portions of the seafloor to push past each other in opposing directions; this lateral movement of seafloors past each other is where transform faults are active. Transform faults move differently from a strike-slip fault at the mid-oceanic ridge. Instead of the ridges moving away from each other, as they do in other strike-slip faults, transform-fault ridges remain in the same, fixed locations, the new ocean seafloor created at the ridges is pushed away from the ridge. Evidence of this motion can be found in paleomagnetic striping on the seafloor. A paper written by geophysicist Taras Gerya theorizes that the creation of the transform faults between the ridges of the mid-oceanic ridge is attributed to rotated and stretched sections of the mid-oceanic ridge.
This occurs over a long period of time with the spreading center or ridge deforming from a straight line to a curved line. Fracturing along these planes forms transform faults; as this takes place, the fault changes from a normal fault with extensional stress to a strike slip fault with lateral stress. In the study done by Bonatti and Crane and gabbro rocks were discovered in the edges of the transform ridges; these rocks are created deep inside the Earth's mantle and rapidly exhumed to the surface. This evidence helps to prove that new seafloor is being created at the mid-oceanic ridges and further supports the theory of plate tectonics. Active transform faults are between faults. Fracture zones represent the active transform-fault lines, which have since passed the active transform zone and are being pushed toward the continents; these elevated ridges on the ocean floor can be traced for hundreds of miles and in some cases from one continent across an ocean to the other continent. The most prominent examples of the mid-oceanic ridge transform zones are in the Atlantic Ocean between South America and Africa.
Known as the St. Paul, Romanche and Ascension fracture zones, these areas have deep identifiable transform faults and ridges. Other locations include: the East Pacific Ridge located in the South Eastern Pacific Ocean, which meets up with San Andreas Fault to the North. Transform faults are not spreading centers; the best example is the San Andreas Fault on the Pacific coast of the United States. The San Andreas Fault links the East Pacific Rise off the West coast of Mexico to the Mendocino Triple Junction off the coast of the Northwestern United States, making it a ridge-to-transform-style fault; the formation of the San Andreas Fault system occurred recently during the Oligocene Period between 34 million and 24 million years ago. During this period, the Farallon plate, followed by the Pacific plate, collided into the North American plate; the collision led to the subduction of the Farallon plate underneath the North American plate. Once the spreading ce