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.
Elevation of the Pacific seafloor, showing the Hawaiian-Emperor seamount chain including Meiji Seamount near top.
|Summit depth||approx. 2,000 m (6,562 ft)|
|Location||North Pacific Ocean, east of the Kamchatka Peninsula|
|Volcanic arc/chain||Hawaiian-Emperor seamount chain|
|Age of rock||82 million years|
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 south of Aleutian Islands (near Russia), at 51°28.80′N 167°36′E It is a seamount in the chain, located north of the hinge of the "V" in the image at right.Detroit Seamount is one of the few seamounts to break the naming scheme of the Emperor seamounts, which are named mostly after emperors or empresses of the Kofun period of Japanese history. It is instead named after the light cruiser USS Detroit.The Detroit Seamount is as big as the island of Hawaii.Hawaii hotspot
The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the best known and intensively studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian–Emperor seamount chain, a 5,800-kilometre (3,600 mi) mostly undersea volcanic mountain range. Four of these volcanoes are active, two are dormant; more than 123 are extinct, most now preserved as atolls or seamounts. The chain extends from south of the island of Hawaiʻi to the edge of the Aleutian Trench, near the eastern coast of Russia.
While most volcanoes are created by geological activity at tectonic plate boundaries, the Hawaii hotspot is located far from plate boundaries. The classic hotspot theory, first proposed in 1963 by John Tuzo Wilson, proposes that a single, fixed mantle plume builds volcanoes that then, cut off from their source by the movement of the Pacific Plate, become increasingly inactive and eventually erode below sea level over millions of years. According to this theory, the nearly 60° bend where the Emperor and Hawaiian segments of the chain meet was caused by a sudden shift in the movement of the Pacific Plate. In 2003, fresh investigations of this irregularity led to the proposal of a mobile hotspot theory, suggesting that hotspots are mobile, not fixed, and that the 47-million-year-old bend was caused by a shift in the hotspot's motion rather than the plate's.
Ancient Hawaiians were the first to recognize the increasing age and weathered state of the volcanoes to the north as they progressed on fishing expeditions along the islands. The volatile state of the Hawaiian volcanoes and their constant battle with the sea was a major element in Hawaiian mythology, embodied in Pele, the deity of volcanoes. After the arrival of Europeans on the island, in 1880–1881 James Dwight Dana directed the first formal geological study of the hotspot's volcanics, confirming the relationship long observed by the natives. The Hawaiian Volcano Observatory was founded in 1912 by volcanologist Thomas Jaggar, initiating continuous scientific observation of the islands. In the 1970s, a mapping project was initiated to gain more information about the complex geology of Hawaii's seafloor.
The hotspot has since been tomographically imaged, showing it to be 500 to 600 km (310 to 370 mi) wide and up to 2,000 km (1,200 mi) deep, and olivine and garnet-based studies have shown its magma chamber is approximately 1,500 °C (2,730 °F). In its at least 85 million years of activity the hotspot has produced an estimated 750,000 km3 (180,000 cu mi) of rock. The chain's rate of drift has slowly increased over time, causing the amount of time each individual volcano is active to decrease, from 18 million years for the 76-million-year-old Detroit Seamount, to just under 900,000 for the one-million-year-old Kohala; on the other hand, eruptive volume has increased from 0.01 km3 (0.002 cu mi) per year to about 0.21 km3 (0.050 cu mi). Overall, this has caused a trend towards more active but quickly-silenced, closely spaced volcanoes—whereas volcanoes on the near side of the hotspot overlap each other (forming such superstructures as Hawaiʻi island and the ancient Maui Nui), the oldest of the Emperor seamounts are spaced as far as 200 km (120 mi) apart.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.Kamchatka-Aleutian Triple Junction
The Kamchatka-Aleutian triple junction is a triple junction of tectonic plates of the Fault-Fault-Trench type where the Pacific Plate, the Okhotsk Plate, and the North American Plate meet. It is located east of the Kamchatka Mys peninsula and west of Bering Island. Meiji Seamount is located to the southeast of the junction.
In the Kamchatka-Aleutian junction, the Kuril–Kamchatka Trench meets the Aleutian Trench. The former is a subduction zone while the latter is a transform fault in its western part.Kula-Farallon Ridge
The Kula-Farallon Ridge was an ancient mid-ocean ridge that existed between the Kula and Farallon plates in the Pacific Ocean during the Jurassic period. There was a small piece of this ridge off the Pacific Northwest 43 million years ago. The rest of the ridge has since been subducted beneath Alaska.
In its early stages of development, the Kula-Farallon Ridge sheared pieces of oceanic rock off the coast of California. When the Kula–Farallon Ridge was in the area where Washington and Oregon are now, basaltic lava erupted there. Some of the basaltic lava is now part of the Olympic Peninsula.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.Nintoku Seamount
Nintoku Seamount or Nintoku Guyot is a seamount (underwater volcano) and guyot (flat top) in the Hawaiian-Emperor seamount chain. It is a large, irregularly shaped volcano that last erupted 66 million years ago. Three lava flows have been sampled at Nintoku Seamount; the flows are almost all alkalic (subaerial) lava. It is 56.2 million years old.Nintoku is positioned a roughly 41 degrees north latitude, approximately two-thirds the way southward along the north-northeast-south-southeast Emperor seamounts extending from Meiji Seamount (about 53°N) in the north to Kammu Seamount (about 32°N) at the chain's southern terminus. Nintoku Seamount was named after the 16th emperor of Japan, Emperor Nintoku, by geologist Robert Dietz in 1954.The seamount occupies a central position in the Emperor Seamount chain and is thus an important point in the paleolatitude history of the Hawaiian hotspot, instrumental to proving the scientific hunch that the Hawaii hotspot was a mobile entity. The structure of the seamount is elongate, aligned north-northwest along the Emperor trend, with two prominent ridges trending southwest and south-southwest as far as 100 km (62 mi) from the main crater. Nintoku Seamount is a plexus of coalesced volcanoes, much like many of the larger seamounts in this chain. The Nintoku system is, however, clearly isolated from Yomei Seamount, about 100 km (62 mi) to the north, and Jingu Seamount, about 200 km (124 mi) to south, by abyssal depths.Outline of oceanography
The following outline is provided as an overview of and introduction to Oceanography.Shield volcano
A shield volcano is a type of volcano usually composed almost entirely of fluid lava flows. It is named for its low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid (low viscosity) lava erupted, which travels farther than lava erupted from a stratovolcano, and results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.Timeline of volcanism on Earth
This timeline of volcanism on Earth is a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic Explosivity Index (VEI) or equivalent sulfur dioxide emission around the Quaternary period (from 2.58 Mya to the present).
Some eruptions cooled the global climate—inducing a volcanic winter—depending on the amount of sulfur dioxide emitted and the magnitude of the eruption. Before the present Holocene epoch, the criteria are less strict because of scarce data availability, partly since later eruptions have destroyed the evidence. Only some eruptions before the Neogene period (from 23 Mya to 2.58 Mya) are listed. Known large eruptions after the Paleogene period (from 66 Mya to 23 Mya) are listed, especially those relating to the Yellowstone hotspot, the Santorini caldera, and the Taupo Volcanic Zone.
Active volcanoes such as Stromboli, Mount Etna and Kilauea do not appear on this list, but some back-arc basin volcanoes that generated calderas do appear. Some dangerous volcanoes in "populated areas" appear many times: so Santorini, six times and Yellowstone hotspot, twenty-one times. The Bismarck volcanic arc, New Britain, and the Taupo Volcanic Zone, New Zealand, appear often too.
In addition to the events listed below, are many examples of eruptions in the Holocene on the Kamchatka Peninsula, which are described in a supplemental table by Peter Ward.