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Hope Basin
The Hope Basin is a geological feature of the Chukchi Sea Shelf. It lies off the Chukchi Sea coast of Alaska. Its area extends from the outer continental shelf of the Seward Peninsula for about westwards off the coast of Chukotka towards Wrangel Island. The Hope Basin is limited on its northeastern side by the Herald Arch (Herald Thrust), a basement uplift cored by Cretaceous thrust faults. The Herald Arch is named after Herald Island. Type: Early Tertiary extensional In any of several fields of study that treat the use of signs — for example, in linguistics, logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid infe ... basin (mainly). References * * Marine geology Landforms of the Chukchi Sea {{regional-geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chukchi Sea Shelf
The Chukchi Shelf or Chukchi Sea Shelf is the westernmost part of the continental shelf of the United States and the easternmost part of the continental shelf of Russia. In the west it merges with the Russian Siberian Shelf. Within this shelf, the 50-mile Chukchi Corridor acts as a passageway for one of the largest marine mammal migrations in the world. The main geological features of the Chukchi Shelf are the Hope Basin and the Herald Thrust, a basement uplift cored by Cretaceous thrust faults. The latter is named after Herald Island. Off the northwestern Alaskan coast there is a Jurassic rift basin, the Hannah Trough. To the north of Alaska the Chukchi Shelf extends to form the Chukchi Plateau which protrudes into the Arctic Ocean geological zone. The Chukchi Shelf is shared between Russia and the United States according to the June 1990 USSR–USA Maritime Boundary Agreement. 50-Mile Chukchi Corridor The Chukchi Corridor is a 50-mile wide strip of ocean offshore of Nor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chukchi Sea
The Chukchi Sea (, ), sometimes referred to as the Chuuk Sea, Chukotsk Sea or the Sea of Chukotsk, is a marginal sea of the Arctic Ocean. It is bounded on the west by the Long Strait, off Wrangel Island, and in the east by Point Barrow, Alaska, beyond which lies the Beaufort Sea. The Bering Strait forms its southernmost limit and connects it to the Bering Sea and the Pacific Ocean. The principal port on the Chukchi Sea is Uelen in Russia. The International Date Line crosses the Chukchi Sea from northwest to southeast. It is displaced eastwards to avoid Wrangel Island as well as the Chukotka Autonomous Okrug on the Russian mainland. Etymology In 1928, during hydrographic observations, the Norwegian polar explorer Harald Sverdrup discovered that the sea lying between Point Barrow and Wrangel Island was very different from the sea between the New Siberian Islands and Wrangel Island and therefore should be separated from the East Siberian Sea. It was decided to call the newly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaska
Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the northernmost, westernmost, and easternmost (the Aleutian Islands cross the 180th meridian into the eastern hemisphere) state in the United States. It borders the Canadian territory of Yukon and the province of British Columbia to the east. It shares a western maritime border, in the Bering Strait, with Russia's Chukotka Autonomous Okrug. The Chukchi and Beaufort Seas of the Arctic Ocean lie to the north, and the Pacific Ocean lies to the south. Technically, it is a semi-exclave of the U.S., and is the largest exclave in the world. Alaska is the largest U.S. state by area, comprising more total area than the following three largest states of Texas, California, and Montana combined, and is the seventh-largest subnational division i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an "''insular shelf''." The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope, surrounded by the flatter continental rise, in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise's gradient is intermediate between the gradients of the slope and the shelf. Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seward Peninsula
The Seward Peninsula is a large peninsula on the western coast of the U.S. state of Alaska whose westernmost point is Cape Prince of Wales. The peninsula projects about into the Bering Sea between Norton Sound, the Bering Strait, the Chukchi Sea, and Kotzebue Sound, just below the Arctic Circle. The entire peninsula is about long and wide. Like Seward, Alaska, it was named after William H. Seward, the United States Secretary of State who fought for the U.S. purchase of Alaska. The Seward Peninsula is a remnant of the Bering land bridge, a roughly thousand-mile-wide swath of land connecting Siberia with mainland Alaska during the Pleistocene Ice Age. This land bridge aided in the migration of humans, as well as plant and animal species, from Asia to North America. Excavations at sites such as the Trail Creek Caves and Cape Espenberg in the Bering Land Bridge National Preserve as well as Cape Denbigh to the south have provided insight into the timeline of prehistorical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chukotka Autonomous Okrug
Chukotka ( ; ), officially the Chukotka Autonomous Okrug, is the easternmost federal subjects of Russia, federal subject of Russia. It is an Autonomous okrugs of Russia, autonomous okrug situated in the Russian Far East, and shares a border with the Sakha Republic to the west, Magadan Oblast to the south-west, and Kamchatka Krai to the south, as well as a Maritime boundary, maritime border on the Bering Strait with the U.S. state of Alaska to the east. Anadyr (town), Anadyr is the largest types of inhabited localities in Russia, town and the administrative center, capital, and the easternmost settlement to have town status in Russia. It is the closest point from Russia to the United States, measuring at 88.51 kilometres or 55 miles. Chukotka is primarily populated by ethnic Russians, Chukchi people, Chukchi, and other Indigenous peoples of Siberia, indigenous peoples. It is the only autonomous okrug in Russia that is not included in, or subordinate to, another federal subject, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wrangel Island
Wrangel Island (, ; , , ) is an island of the Chukotka Autonomous Okrug, Russia. It is the List of islands by area, 92nd-largest island in the world and roughly the size of Crete. Located in the Arctic Ocean between the Chukchi Sea and East Siberian Sea, the island lies astride the 180th meridian, 180th meridian (geography), meridian. The International Date Line is therefore displaced eastwards at this latitude to keep the island, as well as the Chukchi Peninsula on the Russian mainland, on the same day as the rest of Russia. The closest land to Wrangel Island is the tiny and rocky Herald Island (Arctic), Herald Island located to the east.Kosko, M.K., M.P. Cecile, J.C. Harrison, V.G. Ganelin, N.V., Khandoshko, and B.G. Lopatin, 1993Geology of Wrangel Island, Between Chukchi and East Siberian Seas, Northeastern Russia.Bulletin 461, Geological Survey of Canada, Ottawa Ontario, 101 pp. Its straddling the 180th meridian makes its north shore at that point both the northeasternmost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geological period of the entire Phanerozoic. The name is derived from the Latin , 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation . The Cretaceous was a period with a relatively warm climate, resulting in high Sea level#Local and eustatic, eustatic sea levels that created numerous shallow Inland sea (geology), inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was largely ice-free, although there is some evidence of brief periods of glaciation during the cooler first half, and forests extended to the poles. Many of the dominant taxonomic gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or ''window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular '' klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is called a ''blind thrust'' fault. Because of the lack of surface evidence, blind thrust fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herald Island (Arctic)
Herald Island (, ''Ostrov Gerald'') is a small, isolated Russian island in the Chukchi Sea, east of Waring Point, Wrangel Island. It rises in sheer cliffs, making it quite inaccessible, either by ship or by plane. The only bit of accessible shoreline is at its northwestern point, where the cliffs have crumbled into piles of loose rocks and gravel. Its area is and the maximum height above sea level is . The island is unglaciated and uninhabited. It is the northeasternmost point of land in the world. Herald Island belongs administratively to the Chukotka Autonomous Okrug of the Russian Federation. Along with Wrangel Island, Herald Island has been part of the Wrangel Island Wildlife Preserve, a Russian National Park, since 1976. Cape Dmitrieva on Herald Island, marks the easternmost limits of the nature reserve. Herald Island is named after survey vessel HMS Herald (1824), HMS ''Herald'', from which the island was discovered in 1849. Geology Herald Island is composed of sedimen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tertiary Period
The Tertiary ( ) is an obsolete Period (geology), geologic period spanning 66 million to 2.6 or 1.8 million years ago. The period began with the extinction of the non-bird, avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic, Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene, Pliocene Epoch. The Tertiary has not been recognised by the International Commission on Stratigraphy (ICS) since the late 1980s, with the timespan of the Tertiary now being split in to the earlier Paleogene and the more recent Neogene periods, though the Tertiary continues to be used in some scientific publications. Historical use of the term The term Tertiary was first used by Giovanni Arduino (geologist), Giovanni Arduino during the mid-18th century. He classified geologic time into primitive (or primary), secondary, and tertiary periods based on observations of geology in Northern Italy. Later a fourth period, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extensional Tectonics
Extensional tectonics is concerned with the structures formed by, and the Tectonics, tectonic processes associated with, the stretching of a planetary body's Crust (geology), crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter ''β'', known as the ''beta factor'', where : \beta = \frac \,, ''t''0 is the initial crustal thickness and ''t''1 is the final crustal thickness. It is also the equivalent of the Strain (materials science), strain parameter ''stretch''. Low beta factor In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted block faulting, tilted fault blocks. High beta factor In areas of high crustal stretching, individual extensional faults may become rotated to too low a dip to remain active and a new set of faults may be generated. Lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
