The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

that reaches above sea level in

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to

Kure Atoll Kure Atoll (; haw, Hōlanikū, translation=bringing forth heaven; haw, Mokupāpapa, translation=flat island, label=none) or Ocean Island is an atoll in the Pacific Ocean west-northwest of Midway Atoll in the Northwestern Hawaiian Islands ...

, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise a ...

atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gro ...

s, 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 from the Aleutian Trench in the far northwest Pacific to the Kamaʻehuakanaloa Seamount (formerly Lōʻihi), the youngest volcano in the chain, which lies about southeast of the Island of Hawaiʻi.

Regions

The chain can be divided into three subsections. The first, the

Hawaiian archipelago The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost K ...

(also known as the ''Windward isles''), consists of the islands comprising the U.S. state of

. 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 yearsPre-press version
/ref> to 5.1 million years. The island of Hawaii is composed of five volcanoes, of which four ( Kilauea,

Mauna Loa Mauna Loa ( or ; Hawaiian: ; en, Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. The largest subaerial volcano (as opposed to subaqueous volcanoes) in both mass and ...

, Hualalai, and

Mauna Kea Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak ...

) are active. The island of

Maui The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, whic ...

has one active volcano, Haleakalā. Kamaʻehuakanaloa Seamount continues to grow offshore of Hawaii island, 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 The Northwestern Hawaiian Islands or Leeward Hawaiian Islands are a series of islands and atolls in the Hawaiian island chain located northwest (in some cases, far to the northwest) of the islands of Kauai and Niihau. Politically, they are all ...

, collectively referred to as the ''Leeward isles'', the constituents of which are between 7.2 and 27.7 million years old. 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;

, in this group, is the northernmost atoll on Earth. On June 15, 2006, U.S. President George W. Bush issued a proclamation creating

Papahānaumokuākea Marine National Monument The Papahānaumokuākea Marine National Monument (PMNM) (roughly ) is a World Heritage listed U.S. National Monument encompassing of ocean waters, including ten islands and atolls of the Northwestern Hawaiian Islands. It was created in June ...

under the Antiquities Act of 1906. The national monument, meant to protect the biodiversity of the Hawaiian isles,All of the islands in this part of the chain are administrated by Hawaii state, save for

Midway Atoll Midway Atoll (colloquial: Midway Islands; haw, Kauihelani, translation=the backbone of heaven; haw, Pihemanu, translation=the loud din of birds, label=none) is a atoll in the North Pacific Ocean. Midway Atoll is an insular area of the Unit ...

, which is administrated by the U.S. Fish and Wildlife Service. 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. The oldest and most heavily eroded part of the chain are the Emperor seamounts, which are 39 to 85 million years old. 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. 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 A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

and guyots. 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 Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

at the border of

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

Formation

The oldest confirmed age for one of the Emperor Seamounts is 81 million years, for

Detroit Seamount Detroit Seamount, which was formed around 76 million years ago, is one of the oldest seamounts of the Hawaiian-Emperor seamount chain (Meiji Seamount is the oldest, at 82 million years). It lies near the northernmost end of the chain and is sout ...

. However, Meiji Guyot, located to the north of Detroit Seamount, is likely somewhat older. In 1963, geologist

John Tuzo Wilson John Tuzo Wilson (October 24, 1908 – April 15, 1993) was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics. ''Plate tectonics'' is the scientific theory that the rigi ...

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 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 Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With ...

in ancient lava flows sampled at four seamounts (Tarduno ''et al.'', 2003): this evidence from

paleomagnetism Paleomagnetism (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain magnetic minerals in roc ...

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 Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cu ...

over the Hawaii hotspot, an

upwelling Upwelling is an physical oceanography, oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted ...

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 altogether. At that point

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...

of the volcano and

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

of the seafloor cause the volcano to gradually diminish. As the volcano sinks and erodes, it first becomes an atoll island and then an

. Further subsidence causes the volcano to sink below the sea surface, becoming a

and/or a

guyot In marine geology, a guyot (pronounced ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than below the surface of the sea. The diameters of these flat summits can exceed .

Regions

Formation

Aging

See also

Notes

References

Further reading