Hawaiian–Emperor seamount chain

The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean. The seamount chain, containing over 80 identified undersea volcanoes, stretches about 6,200 kilometres (3,900 mi) from the Aleutian Trench in the far northwest Pacific to the Loʻihi seamount, the youngest volcano in the chain, which lies about 35 kilometres (22 mi) southeast of the Island of Hawaiʻi.

Hawaiian-Emperor seamount chain
Hawaiian Islands
Mauna Kea from the ocean
Mauna Kea, the range's highest point
Highest point
PeakMauna Kea (Hawaii, United States)
Elevation4,207 m (13,802 ft)
Coordinates19°49′14″N 155°28′05″W / 19.82056°N 155.46806°WCoordinates: 19°49′14″N 155°28′05″W / 19.82056°N 155.46806°W
Dimensions
Length5,800 km (3,600 mi) NE-SW
Geography
Hawaii hotspot
Elevation of the Pacific seafloor, showing the Hawaiian-Emperor seamount chain stretching northwest from the Hawaiian Islands
CountryUnited States
StateHawaii
Geology
OrogenyHawaii hotspot

Regions

The chain can be divided into three subsections. The first, the Hawaiian archipelago (also known as the Windward isles), consists of the islands comprising the U.S. state of Hawaii. As it is the closest to the hotspot, this volcanically active region is the youngest part of the chain, with ages ranging from 400,000 years[1] to 5.1 million years.[2] The island of Hawaiʻi is composed of five volcanoes, of which three (Kilauea, Mauna Loa, and Hualalai) are still active. Haleakalā on the island of Maui is dormant. Lōʻihi Seamount continues to grow offshore of Hawaiʻi island, and is the only known volcano in the chain in the submarine pre-shield stage.[3]

The second part of the chain is composed of the Northwestern Hawaiian Islands, collectively referred to as the Leeward isles, the constituents of which are between 7.2 and 27.7 million years in age.[2] Erosion has long since overtaken volcanic activity at these islands, and most of them are atolls, atoll islands, and extinct islands. They contain many of the most northerly atolls in the world; Kure Atoll, in this group, is the northernmost atoll on Earth.[4] On June 15, 2006, U.S. President George W. Bush issued a proclamation creating Papahānaumokuākea Marine National Monument under the Antiquities Act of 1906. The national monument, meant to protect the biodiversity of the Hawaiian isles,[n 1] encompasses all of the northern isles, and is one of the largest such protected areas in the world. The proclamation limits tourism to the area, and called for a phase-out of fishing by 2011.[5]

The oldest and most heavily eroded part of the chain are the Emperor seamounts, which are 39[6] to 85 million years in age.[7] The Emperor and Hawaiian chains form an 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.[8] The issue is still currently under academic debate.[9] 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 terminates at the Kuril–Kamchatka Trench, a subduction zone at the border of Russia.[10]

Formation

Hawaiian seamount chain
The Hawaiian-Emperor seamount chain, zoomed in on the current habitable islands

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 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[11] 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 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 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.

Aging

The chain has been produced by the movement of the ocean crust over the Hawaiʻi hotspot, an upwelling of hot rock from the Earth's mantle. As the oceanic crust moves the volcanoes farther away from their source of magma, their eruptions become less frequent and less powerful until they eventually cease to erupt altogether. At that point erosion of the volcano and subsidence of the seafloor cause the volcano to gradually diminish. As the volcano sinks and erodes, it first becomes an atoll island and then an atoll. Further subsidence causes the volcano to sink below the sea surface, becoming a seamount and/or a guyot.[3]

See also

Notes

  1. ^ All of the islands in this part of the chain are administrated by Hawaii state, save for Midway Atoll, which is administrated by the U.S. Fish and Wildlife Service.

References

  1. ^ Michael O. Garcia, Jackie Caplan-Auerbanch, Eric H. De Carlo, M.D. Kurz, N. Becker (September 20, 2005). "Geology, geochemistry and earthquake history of Lōʻihi Seamount, Hawaiʻi". Chemie der Erde - Geochemistry. This is the pre-press version of a paper that was published on 2006-05-16 as "Geochemistry, and Earthquake History of Lōʻihi Seamount, Hawaiʻi's youngest volcano", in Chemie der Erde – Geochemistry (66) 2:81–108. University of Hawaii – School of Ocean and Earth Science and Technology. 66 (2): 81–108. Bibcode:2006ChEG...66...81G. doi:10.1016/j.chemer.2005.09.002. hdl:1912/1102.CS1 maint: uses authors parameter (link) Pre-press version
  2. ^ a b Rubin, Ken. "The Formation of the Hawaiian Islands". Hawaii Center for Vulcanology. Retrieved May 18, 2009.
  3. ^ a b "Evolution of Hawaiian Volcanoes". Hawaiian Volcano Observatory (USGS). September 8, 1995. Retrieved March 7, 2009.
  4. ^ "Kure Atoll". Public Broadcasting System – KQED. March 22, 2006. Retrieved June 13, 2009.
  5. ^ Staff authors (June 15, 2006). "Bush creates new marine sanctuary". BBC News. Retrieved December 14, 2009.
  6. ^ Sharp, W. D.; Clague, DA (2006). "50-Ma Initiation of Hawaiian-Emperor Bend Records Major Change in Pacific Plate Motion". Science. 313 (5791): 1281–84. Bibcode:2006Sci...313.1281S. doi:10.1126/science.1128489. PMID 16946069.
  7. ^ Regelous, M.; Hofmann, A.W.; Abouchami, W.; Galer, S.J.G. (2003). "Geochemistry of Lavas from the Emperor Seamounts, and the Geochemical Evolution of Hawaiian Magmatism from 85 to 42 Ma" (PDF). Journal of Petrology. 44 (1): 113–140. Bibcode:2003JPet...44..113R. doi:10.1093/petrology/44.1.113. Archived from the original (PDF) on July 19, 2011. Retrieved July 23, 2010.
  8. ^ John Roach (August 14, 2003). "Hot Spot That Spawned Hawaii Was on the Move, Study Finds". National Geographic News. Retrieved March 9, 2009.
  9. ^ Sharp et al., 2006, Initiation of the bend near Kimmei seamount about 50 million years ago (MA) was coincident with realignment of Pacific spreading centers and early magmatism in western Pacific arcs, consistent with formation of the bend by changed Pacific plate motion.
  10. ^ G. R. Foulger; Don L. Anderson. "The Emperor and Hawaiian Volcanic Chains: How well do they fit the plume hypothesis?". MantlePlumes.org. Retrieved April 1, 2009.
  11. ^ "origin of the Hawaiian Islands". Pubs.usgs.gov. 2013-01-04. Retrieved 2013-01-12.

Further reading

Abbott Seamount

Abbott Seamount is a seamount lying within the Hawaiian-Emperor seamount chain in the northern Pacific Ocean. It erupted 36-40 million years ago.Position is 31° 48' 00" N, 174° 18' 00" E

Colahan Seamount

Colahan Seamount is a seamount lying within the Hawaiian-Emperor seamount chain in the northern Pacific Ocean. It erupted 37-40 million years ago.

Daikakuji Guyot

Daikakuji Seamount is a seamount (underwater volcano) and the southwesternmost volcanic feature in the Hawaiian Emperor chain bend area.

Hancock Seamount

Hancock Seamount is a seamount of the Hawaiian-Emperor seamount chain in the Pacific Ocean.

It was formed in the Eocene and Oligocene epochs of the Paleogene Period. The last eruption from Hancock Seamount is unknown.

Jingū Seamount

Jingū Seamount, also called Jingū Guyot, is a guyot of the Hawaiian-Emperor seamount chain in the Pacific Ocean. It erupted 55 million years ago. The seamount is elongated in structure, running north–south, and has an oval shaped crater in the center, which is evidence of collapse when above sea level.The seamount was named in 1954 by Robert S. Dietz, after Japanese Empress Jingū.

Kaena Ridge

Kaena Ridge, also referred to as the Kaena Volcano, is a submerged remnant of an ancient shield volcano that is to the north of and once comprised the northern section of the Hawaiian Island of Oʻahu. Ka'ena Ridge was the oldest of the three volcanoes to form Oahu and it was also the shortest when it grew out of sea level. It was about 3,000 ft.

Kammu Seamount

Kanmu Seamount is a seamount lying within the Hawaiian-Emperor seamount chain in the Pacific Ocean. The last eruption of Kanmu Seamount is unknown.

Kimmei Seamount

Kimmei Seamount is a seamount of the Hawaiian-Emperor seamount chain in the northern Pacific Ocean. It last erupted about 40 million years ago.

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 200 km (124 mi) 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 9 km (6 mi) thick portion of the Pacific Plate. The oldest rock from the north side of Koko Seamount is dated at 52.6 and the south side of Koko at 50.4 million years ago. To the southeast of the bend is Kimmei Seamount at 47.9 million years ago and southeast of it, Daikakuji at 46.7.

Lisianski Island

Lisianski Island (Hawaiian: Papa‘āpoho) is one of the Northwestern Hawaiian Islands, with a land area of 384.425 acres (155.571 ha) and a maximum elevation of 40 feet (12 m) above sea level. It is a low, flat sand and coral island about 905 nautical miles (1,676 km) northwest of Honolulu. The island is surrounded by reefs and shoals, including the extensive Neva Shoals. Access to the island is limited by helicopter or by boat to a narrow sandy inlet on the southeastern side of the island.

List of volcanoes in the Hawaiian – Emperor seamount chain

The Hawaiian–Emperor seamount chain is a series of volcanoes and seamounts extending about 6,200 km across the Pacific Ocean. The chain has been produced by the movement of the ocean crust over the Hawaiʻi hotspot, an upwelling of hot rock from the Earth's mantle. As the oceanic crust moves the volcanoes farther away from their source of magma, their eruptions become less frequent and less powerful until they eventually cease to erupt altogether. At that point, erosion of the volcano and subsidence of the seafloor cause the volcano to gradually diminish. As the volcano sinks and erodes, it first becomes an atoll island and then an atoll. Further subsidence causes the volcano to sink below the sea surface, becoming a seamount and/or a guyot. This list documents the most significant volcanoes in the chain, ordered by distance from the hotspot; however, there are many others that have yet to be properly studied.

The chain can be divided into three subsections. The first, the Hawaiian archipelago (also known as the Windward isles), consists of the islands comprising the U.S. state of Hawaiʻi (not to be confused with the island of Hawaiʻi). As it is the closest to the hotspot, this volcanically active region is the youngest part of the chain, with ages ranging from 400,000 years to 5.1 million years. The island of Hawaiʻi is comprised by five volcanoes, of which two (Kilauea and Mauna Loa) are still active. Lōʻihi Seamount continues to grow offshore, and is the only known volcano in the chain in the submarine pre-shield stage.The second part of the chain is composed of the Northwestern Hawaiian Islands, collectively referred to as the Leeward isles, the constituents of which are between 7.2 and 27.7 million years in age. Erosion has long since overtaken volcanic activity at these islands, and most of them are atolls, atoll islands, and extinct islands. They contain many of the most northerly atolls in the world; one of them, Kure Atoll, is the northern-most atoll in the world.The oldest and most heavily eroded part of the chain are the Emperor seamounts, which are 39 to 85 million years in age. The Emperor and Hawaiian chains are separated by a large L-shaped bend that causes the orientations of the chains to differ by about 60°. This bend was long attributed to a relatively sudden change 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 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 terminates at the Kuril–Kamchatka Trench, a subduction zone at the border of Russia.

Maro Reef

Maro Reef (Hawaiian: Nalukākala - "surf that arrives in combers") is a largely submerged coral atoll located in the Northwestern Hawaiian Islands. It was discovered in 1820 by Captain Joseph Allen of the ship Maro, after whose ship the reef was named. With a total area of 747 square miles (1,935 km2), it is the largest coral reef in the Northwestern Hawaiian Islands. It contains 37 species of stony coral. Unlike most atolls, the coral extends out from the center like spokes on a wheel. Located about 850 miles (740 nmi; 1,370 km) northwest of Honolulu, Hawaii, Maro Reef contains about 1 acre (4,000 m2) of dry land which itself can be submerged depending on the tides. Some scientists believe that it "may be on the verge of drowning" because the reefs are detached and are vulnerable to strong storm waves.USNS Mission San Miguel (T-AO-129) ran aground on the reef, while running at full speed and in ballast, and sank on October 8, 1957.

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 of a particular type of seamount known as a guyot, and some publications refer to it as Meiji Guyot.

Meiji Seamount will eventually be destroyed by subduction into the Kuril-Kamchatka Trench where it is carried by the ongoing plate motion, although this will not fully occur for several million more years if the current rate of motion is maintained. Although Meiji is the oldest extant seamount in the Hawaii-Emperor chain, the question of whether there were older seamounts in the chain which have already been subducted into the trench remains open, and is the subject of ongoing scientific research.

The Deep Sea Drilling Project (DSDP) Leg 19, Hole 192A, recovered 13 m (43 ft) of pillow lava from near the summit of Meiji. The lavas were initially classified as alkali basalts on the basis of their mineralogy, but subsequent microprobe analyses of glass and pyroxene suggested that they are tholeiitic in origin. At least five flows were found.

Māhukona

Māhukona is a submerged shield volcano on the northwestern flank of the Island of Hawaiʻi. A drowned coral reef at about 3,770 feet (-1,150 m) below sea level and a major break in slope at about 4,400 feet (-1,340 m) below sea level represent old shorelines. The summit of the shield volcano was once 800 feet (250 m) above sea level. It has now subsided below sea level. A roughly circular caldera marks the summit of Māhukona. A prominent rift zone extends to the west. A second rift zone probably extended to the east but has been buried by younger volcanoes. The main shield-building stage of volcanism ended about 470,000 years ago. The summit of the shield volcano subsided below sea level between 435,000 and 365,000 years ago.

This makes Māhukona the oldest volcano to build Hawaiʻi island, compared to Kohala to the east and Mauna Kea to the east. The Monterey Bay Aquarium Research Institute investigated the area with a remotely controlled submarine in 2001.It was named for the area known as Māhukona, on the shore to the northeast.

Ojin Seamount

Ōjin Seamount, also called Ōjin Guyot, named after Emperor Ōjin, 15th Emperor of Japan, is a guyot of the Hawaiian-Emperor seamount chain in the Pacific Ocean. It erupted 55 million years ago.

Penguin Bank

Penguin Bank is the name given to a now-submerged shield volcano of the Hawaiian Islands. Its coral-capped remains lie immediately west of the island of Molokaʻi, under relatively shallow water (see bathymetric map at the right).

Suiko Seamount

Suiko Seamount, also called Suiko Guyot, is a guyot of the Hawaiian-Emperor seamount chain in the Pacific Ocean.

Yomei Seamount

Yomei Seamount is a seamount of the Hawaiian-Emperor seamount chain in the northern Pacific Ocean.

Its eruption ages are unknown, but the seamounts on either side are in the 56.2 to 59.6 million range during the Paleogene Period.

Yuryaku Seamount

Yuryaku Seamount (also called Yuryaku Guyot) is a seamount (underwater volcano) and guyot (flat-topped) located northwest of Hawaii. It is located a little southwest of the V-shaped bend separating the Emperor Seamounts from the older Hawaiian islands, all of the Hawaiian-Emperor seamount chain in the North Pacific Ocean.

Windward
Isles
Leeward
Isles
EmperorSeamounts
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