Seafloor spreading
Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics. When oceanic plates diverge, tensional stress causes fractures to occur in the lithosphere. The motivating force for seafloor spreading ridges is tectonic plate pull rather than magma pressure, although there is typically significant magma activity at spreading ridges. At a spreading center basaltic magma rises up the fractures and cools on the ocean floor to form new seabed. Hydrothermal vents are common at spreading centers. Older rocks will be found farther away from the spreading zone while younger rocks will be found nearer to the spreading zone. Additionally spreading rates determine if the ridge is a fast, intermediate, or slow. As a general rule, fast ridges see spreading rate of more than 9 cm / year. Intermediate ridges have a spreading rate of 4 -- 9 cm / year while slow spreading ridges have a rate less than 4 cm / year.
Antarctica
Emilio Marcos Palma was the first person born south of the 60th parallel south (the continental limit according to the Antarctic Treaty), as well as the first one born on the Antarctic mainland, in 1978 at Base Esperanza, on the tip of the Antarctic Peninsula; his parents were sent there along with seven other families by the Argentine government to determine if the continent was suitable for family life. In 1984, Juan Pablo Camacho was born at the Frei Montalva Station, becoming the first Chilean born in Antarctica. Several bases are now home to families with children attending schools at the station. As of 2009, eleven children were born in Antarctica (south of the 60th parallel south): eight at the Argentine Esperanza Base and three at the Chilean Frei Montalva Station.
Vesta Nunataks
The Vesta Nunataks () is a small group of nunataks rising to about 1,200 m, lying between Grikurov Ridge in the LeMay Range and Aeolus Ridge in Planet Heights, situated near the east coast of Alexander Island, Antarctica. In association with the names of planets and their satellites in this area, they were named after Vesta, an asteroid that lies between the orbits of Mars and Jupiter. They were named by United Kingdom Antarctic Place-Names Committee in 1987.
Air mass
Tropical and equatorial air masses are hot as they develop over lower latitudes. Those that develop over land (continental) are drier and hotter than those that develop over oceans, and travel poleward on the western periphery of the subtropical ridge. Maritime tropical air masses are sometimes referred to as trade air masses. Monsoon air masses are moist and unstable. Superior air masses are dry, and rarely reach the ground. They normally reside over maritime tropical air masses, forming a warmer and drier layer over the more moderate moist air mass below, forming what is known as a trade wind inversion over the maritime tropical air mass. Continental Polar air masses (cP) are air masses that are cold and dry due to their continental source region. Continental polar air masses that affect North America form over interior Canada. Continental Tropical air masses (cT) are a type of tropical air produced by the subtropical ridge over large areas of land and typically originate from low - latitude deserts such as the Sahara Desert in northern Africa, which is the major source of these air masses. Other less important sources producing cT air masses are the Arabian Peninsula, the central arid / semi-arid part of Australia and deserts lying in the Southwestern United States. Continental tropical air masses are extremely hot and dry.
Geological history of Earth
The Cambrian is a major division of the geologic timescale that begins about 541.0 ± 1.0 Ma. Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. The waters of the Cambrian period appear to have been widespread and shallow. Continental drift rates may have been anomalously high. Laurentia, Baltica and Siberia remained independent continents following the break-up of the supercontinent of Pannotia. Gondwana started to drift toward the South Pole. Panthalassa covered most of the southern hemisphere, and minor oceans included the Proto-Tethys Ocean, Iapetus Ocean and Khanty Ocean.
Seafloor spreading
Earlier theories (e.g. by Alfred Wegener and Alexander du Toit) of continental drift postulated that continents ``ploughed ''through the sea. The idea that the seafloor itself moves (and also carries the continents with it) as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s. The theory is well accepted now, and the phenomenon is known to be caused by convection currents in the asthenosphere, which is ductile, or plastic, and the brittle lithosphere.
Continental shelf
The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise. 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 slope and the shelf, on the order of 0.5 -- 1 °.
Conscription in the United States
In colonial times, the Thirteen Colonies used a militia system for defense. Colonial militia laws -- and after independence those of the United States and the various states -- required able - bodied males to enroll in the militia, to undergo a minimum of military training, and to serve for limited periods of time in war or emergency. This earliest form of conscription involved selective drafts of militiamen for service in particular campaigns. Following this system in its essentials, the Continental Congress in 1778 recommended that the states draft men from their militias for one year's service in the Continental army; this first national conscription was irregularly applied and failed to fill the Continental ranks.
Seafloor spreading
Earlier theories (e.g. by Alfred Wegener and Alexander du Toit) of continental drift postulated that continents ``ploughed ''through the sea. The idea that the seafloor itself moves (and also carries the continents with it) as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s. The theory is well accepted now, and the phenomenon is known to be caused by convection currents in the asthenosphere, which is ductile, or plastic, and the brittle lithosphere (crust and upper mantle).
Mesozoic
Compared to the vigorous convergent plate mountain-building of the late Paleozoic, Mesozoic tectonic deformation was comparatively mild. The sole major Mesozoic orogeny occurred in what is now the Arctic, creating the Innuitian orogeny, the Brooks Range, the Verkhoyansk and Cherskiy Ranges in Siberia, and the Khingan Mountains in Manchuria. This orogeny was related to the opening of the Arctic Ocean and subduction of the North China and Siberian cratons under the Pacific Ocean. Nevertheless, the era featured the dramatic rifting of the supercontinent Pangaea. Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast) today.
South American Plate
The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-Atlantic Ridge.
List of island countries
This is a list of island countries. An island is a land mass (smaller than a continent) that is surrounded by water. Many island countries are spread over an archipelago, as is the case with the Federated States of Micronesia and the Indonesia (which consists of thousands of islands). Others consist of a single island, such as Nauru, or part of an island, such as Haiti. Although Australia is designated as a continent, it is often referred to as an island, as it has no land borders. Some declared island countries are not universally recognized as politically independent, such as Northern Cyprus. Some states, such as Taiwan, officially claim to hold continental territories but are de facto limited to control over islands.
Pavie Ridge
Pavie Ridge or Cap Pavie or Île Pavie is a rocky ridge located at in Antarctica which rises over 500 m. It extends south and west from Martin Glacier to Moraine Cove, and forms the southeastern limit of the Bertrand Ice Piedmont, on the west coast of Graham Land.
World Park Base
World Park Base was a non-governmental year-round Antarctic base located at Cape Evans on Ross Island in the Ross Dependency. The international environmental organization Greenpeace established World Park Base in 1987 in order to press its demand for the Antarctic Treaty nations to declare all of the continent of Antarctica a World Park. This would make the entire continent off-limits to commercial exploitation and pollution, and permit only limited scientific research. Greenpeace closed down and completely dismantled the base in 1992.
Africa
Africa is the world's second largest and second most - populous continent (behind Asia in both categories). At about 30.3 million km (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area and 20% of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognised sovereign states (countries), nine territories and two de facto independent states with limited or no recognition. The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.
Antarctica
Due to its location at the South Pole, Antarctica receives relatively little solar radiation. This means that it is a very cold continent where water is mostly in the form of ice. Precipitation is low (most of Antarctica is a desert) and almost always in the form of snow, which accumulates and forms a giant ice sheet which covers the land. Parts of this ice sheet form moving glaciers known as ice streams, which flow towards the edges of the continent. Next to the continental shore are many ice shelves. These are floating extensions of outflowing glaciers from the continental ice mass. Offshore, temperatures are also low enough that ice is formed from seawater through most of the year. It is important to understand the various types of Antarctic ice to understand possible effects on sea levels and the implications of global cooling.
La Coulotte Ridge
La Coulotte Ridge is located on the border of Alberta and British Columbia on the Continental Divide. It was named after La Coulotte in France.
Grikurov Ridge
Grikurov Ridge () is a ridge that extends westward for about from the south end of the LeMay Range, in central Alexander Island, Antarctica. The feature was mapped from trimetrogon air photography taken by the Ronne Antarctic Research Expedition, 1947–48, and from survey by the Falkland Islands Dependencies Survey, 1948–50. It was named by the UK Antarctic Place-Names Committee for the Russian Garrik Grikurov, a Soviet exchange geologist with the British Antarctic Survey, who worked in this area in 1963–64.
Continental shelf
The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise. 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 slope and the shelf.
Hoosier Pass
The pass is located on the Continental Divide at the northern end of the Mosquito Range, in a gap between Mount Lincoln (west) and Hoosier Ridge (east). It sits on the boundary between Park (south) and Summit (north) counties.
Where is the continental limit of the continent on which Grikurov Ridge is located?
Grikurov Ridge >> continent
Antarctica
Where is the continental limit of #1 ?
60th parallel south