The
Hawaiian-Emperor seamount chain is composed of the
Hawaiian RidgeThe Hawaiian Islands are an archipelago of 19 islands and atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll. Excluding Midway, which is an unincorporated territory of the...
, consisting of the islands of the Hawaiian chain northwest to
Kure AtollKure Atoll or Ocean Island lies some beyond Midway Atoll in the Northwestern Hawaiian Islands at . The International Date Line lies approximately 100 miles to the west. Kure is the northern-most coral atoll in the world...
, and the Emperor Seamounts, a vast underwater mountain region of islands and intervening
seamountA seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000–4,000 meters depth...
s,
atollAn atoll is an island of coral that encircles a lagoon partially or completely.- Usage :The word atoll comes from the Dhivehi word atholhu
OED. Its first recorded use in English was in 1625 as atollon...
s, shallows, banks and reefs along a line trending southeast to northwest beneath the northern
Pacific OceanThe Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarctica in the south, bounded by Asia and...
. The seamount chain, containing over 80 identified undersea volcanoes, stretches over from the
Aleutian TrenchThe Aleutian Trench is a subduction zone and oceanic trench which runs along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. It is classified as a "marginal trench" in the east as it runs along the margin of the continent, and...
in the far northwest Pacific to the
Loʻihi seamountLōihi Seamount is an active undersea volcano located around off the southeast coast of the island of Hawaii. It lies on the flank of Mauna Loa, the largest shield volcano on Earth. Lōihi Seamount is the newest volcano in the Hawaiian-Emperor seamount chain, a string of volcanoes that stretches...
, the youngest volcano in the chain, which lies about southeast of the
Island of HawaiʻiThe Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the U.S. State of Hawaii in the North Pacific Ocean...
.
The
Hawaiian-Emperor seamount chain is composed of the
Hawaiian RidgeThe Hawaiian Islands are an archipelago of 19 islands and atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll. Excluding Midway, which is an unincorporated territory of the...
, consisting of the islands of the Hawaiian chain northwest to
Kure AtollKure Atoll or Ocean Island lies some beyond Midway Atoll in the Northwestern Hawaiian Islands at . The International Date Line lies approximately 100 miles to the west. Kure is the northern-most coral atoll in the world...
, and the Emperor Seamounts, a vast underwater mountain region of islands and intervening
seamountA seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000–4,000 meters depth...
s,
atollAn atoll is an island of coral that encircles a lagoon partially or completely.- Usage :The word atoll comes from the Dhivehi word atholhu
OED. Its first recorded use in English was in 1625 as atollon...
s, shallows, banks and reefs along a line trending southeast to northwest beneath the northern
Pacific OceanThe Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarctica in the south, bounded by Asia and...
. The seamount chain, containing over 80 identified undersea volcanoes, stretches over from the
Aleutian TrenchThe Aleutian Trench is a subduction zone and oceanic trench which runs along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. It is classified as a "marginal trench" in the east as it runs along the margin of the continent, and...
in the far northwest Pacific to the
Loʻihi seamountLōihi Seamount is an active undersea volcano located around off the southeast coast of the island of Hawaii. It lies on the flank of Mauna Loa, the largest shield volcano on Earth. Lōihi Seamount is the newest volcano in the Hawaiian-Emperor seamount chain, a string of volcanoes that stretches...
, the youngest volcano in the chain, which lies about southeast of the
Island of HawaiʻiThe Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the U.S. State of Hawaii in the North Pacific Ocean...
. The
Hawaiian IslandsThe Hawaiian Islands are an archipelago of 19 islands and atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll. Excluding Midway, which is an unincorporated territory of the...
are that portion of the Hawaiian-Emperor seamount chain that projects above sea level.
In 1963, geologist
John Tuzo WilsonJohn Tuzo Wilson, CC, OBE, FRS, FRSC, FRSE was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics....
hypothesized the origins of the Hawaiian-Emperor seamount chain, explaining that they were created by a
hotspotIn geology, a hotspot is a location on the Earth's surface that has experienced active volcanism for a long period of time.-Characteristics:...
of volcanic activity that was essentially stationary as the
Pacific tectonic plateThe Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.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...
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 would mark 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".
More recent studies, mentioned below, provide evidence that the change in direction may have occurred over a period of about 8 million years. Yet more recently published
argon-argonArgon-argon dating is a radiometric dating method invented to supersede potassium-argon dating in accuracy. In this technique, the decay of 40K to 40Ar* is used to date geological events, particularly the eruption and cooling of igneous rocks and minerals...
ages of rocks from volcanoes of the southern and central Emperor chain better establish the age at which the bend formed. Sharp and Clague (2006) determined that the bend initiated at about 50 million years ago, and the bending continued until about 42 million years ago. They also concluded that the bend formed from a "traditional" cause—a change in the direction of motion of the Pacific plate.
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
magnetiteMagnetite is a ferrimagnetic mineral with chemical formula Fe
3O
4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name ferrous-ferric oxide...
in ancient lava flows sampled at four seamounts (Tarduno
et al., 2003): this evidence from
paleomagnetismPaleomagnetism is the study of the record of the Earth's magnetic field preserved in various magnetic minerals through time. The study of paleomagnetism has demonstrated that the Earth's magnetic field varies substantially in both orientation and intensity through time.A paleomagnetist is a...
shows a more complex relationship than the commonly accepted view of a stationary hotspot. If the hotspot had remained above a fixed
mantle plumeA mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. As the heads of mantle plumes can partly melt when they reach shallow depths, they are thought to be the cause of volcanic centers known as hotspots and probably also to have caused flood basalts...
during the past 80 million years, the latitude as recorded by the orientation of the ancient magnetic field preserved by magnetite should be constant for each sample and should also signify original cooling at the same latitude as the current Big Island of Hawaii. Comparisons with the traces of other hotspots also test if the Hawaiian-Emperor bend records a change in plate motion. 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.
See also
- Meiji Seamount
Meiji Seamount 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...
- Detroit Seamount
Detroit Seamount, which was formed around 76 million years ago, is one of the oldest seamounts of the Hawaiian-Emperor seamount chain...
- Pacific-Kula Ridge
The Pacific-Kula Ridge is a former mid-ocean ridge that existed between the Pacific and Kula plates in the Pacific Ocean during the early Tertiary period. Its appearance was in an east-west direction and the Hawaiian-Emperor seamount chain had its attribution with the ridge...
- New England Seamount chain
The New England Seamount chain is an underwater chain of seamounts in the Atlantic Ocean stretching over 1,000 kilometers from the edge of the Georges Bank off the coast of Massachusetts. The chain consists of over twenty extinct volcanic peaks, many rising over 4,000 meters from the seabed...
- Kodiak-Bowie Seamount chain
The Kodiak-Bowie Seamount chain, also called the Pratt-Welker Seamount chain, is a seamount chain in southeastern Gulf of Alaska stretching from the Aleutian Trench in the north to Bowie Seamount, the youngest volcano in the chain, which lies west of the Queen Charlotte Islands, British Columbia,...
- 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....
- Plate tectonics
Plate tectonics is a theory which describes the large scale motions of Earth's lithosphere...
- Isostasy
Isostasy is a term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density. This concept is invoked to explain how different topographic...
- Oceanic trench
The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor....
External links