In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.
The contiguous United States consists of the 48 adjoining U.S. states and the District of Columbia of the United States of America in central North America. The term excludes the only two non-contiguous states, which are Alaska and Hawaii, and all other offshore insular areas, such as the U.S. territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. The colloquial term "Lower 48" is also used, especially in relation to Alaska.
In geography, a pole of inaccessibility is the farthest location in a given landmass, sea, or other topographical feature, starting from a given boundary, relative to a given criterion. A geographical criterion of inaccessibility marks a location that is the most challenging to reach according to that criterion. Often it refers to the most distant point from the coastline, implying the farthest point into a landmass from the shore, or the farthest point into a body of water from the shore. In these cases, a pole of inaccessibility is the center of a maximally large circle that can be drawn within an area of interest only touching but not crossing a coastline. Where a coast is imprecisely defined, the pole will be similarly imprecise.
Geography of Asia reviews geographical concepts of classifying Asia, comprising 58 countries and territories.
Determining the boundaries between the continents is generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered seven but may range as low as four when Afro-Eurasia and the Americas are both considered as single continents. An island can be considered to be associated with a given continent by either lying on the continent's adjacent continental shelf or being a part of a microcontinent on the same principal tectonic plate. An island can also be entirely oceanic while still being associated with a continent by geology or by common geopolitical convention. Another example is the grouping into Oceania of the Pacific Islands with Australia and Zealandia.
Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin.
Tricontinental Chile is a geopolitical concept denoting Chile's unique position with its mainland in South America, Easter Island in Oceania (Polynesia) and the Chilean Antarctic Territory in Antarctica. This concept is built on the basis that there are Chilean territories as far away from the mainland as to be considered part of Polynesia and on a larger scale, Oceania, and Chile's claims to Antarctica provide it a basis for claiming to be a part of Antarctica as well.
The geography of Australia encompasses a wide variety of biogeographic regions being the world's smallest continent, while comprising the territory of the sixth-largest country in the world. The population of Australia is concentrated along the eastern and south-eastern coasts. The geography of the continent is extremely diverse, ranging from the snow-capped mountains of the Australian Alps and Tasmania to large deserts, tropical and temperate forests, grasslands, heathlands and woodlands.
Zealandia, also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83–79 million years ago. It has been described variously as a submerged continent, continental fragment, and microcontinent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is over a billion years old, about twice as old as geologists previously thought.
Afro-Eurasia is a landmass comprising the continents of Africa, Europe, and Asia. The terms are compound words of the names of its constituent parts. Afro-Eurasia has also been called the "Old World", in contrast to the "New World" referring to the Americas.
A continent is any of several large geographical regions. Continents are generally identified by convention rather than any strict criteria. A continent could be a single landmass or a part of a very large landmass, as in the case of Asia or Europe. Due to this, the number of continents varies; up to seven or as few as four geographical regions are commonly regarded as continents. Most English-speaking countries recognize seven regions as continents. In order from largest to smallest in area, these seven regions are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Different variations with fewer continents merge some of these regions; examples of this are merging North America and South America into America, Asia and Europe into Eurasia, and Africa, Asia, and Europe into Afro-Eurasia.
Pangaea or Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic and beginning of the Jurassic. Pangaea was C-shaped, with the bulk of its mass stretching between Earth's northern and southern polar regions and surrounded by the superocean Panthalassa and the Paleo-Tethys and subsequent Tethys Oceans. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists.
The continent of Australia, sometimes known in technical contexts by the names Sahul, Australia-New Guinea, Australinea, or Meganesia to distinguish it from the country of Australia, is located within the Southern and Eastern hemispheres. The continent includes mainland Australia, Tasmania, the island of New Guinea, the Aru Islands, the Ashmore and Cartier Islands, most of the Coral Sea Islands, and some other nearby islands. Situated in the geographical region of Oceania, Australia is the smallest of the seven traditional continents.
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of 20,327,000 km2 (7,848,000 sq mi), it is the second-smallest of the five principal oceanic divisions, smaller than the Pacific, Atlantic and Indian oceans, and larger than the Arctic Ocean.
A submerged continent or a sunken continent is a region of continental crust, extensive in size but mainly undersea. The terminology is used by some paleogeologists and geographers in reference to some landmasses.
A paleocontinent or palaeocontinent is a distinct area of continental crust that existed as a major landmass in the geological past. There have been many different landmasses throughout Earth's time. They range in sizes; some are just a collection of small microcontinents while others are large conglomerates of crust. As time progresses and sea levels rise and fall more crust can be exposed making way for larger landmasses. The continents of the past shaped the evolution of organisms on Earth and contributed to the climate of the globe as well. As landmasses break apart, species are separated and those that were once the same now have evolved to their new climate. The constant movement of these landmasses greatly determines the distribution of organisms on Earth's surface. This is evident with how similar fossils are found on completely separate continents. Also, as continents move, mountain building events (orogenies) occur, causing a shift in the global climate as new rock is exposed and then there is more exposed rock at higher elevations. This causes glacial ice expansion and an overall cooler global climate. The movement of the continents greatly affects the overall dispersal of organisms throughout the world and the trend in climate throughout Earth's history. Examples include Laurentia, Baltica and Avalonia, which collided together during the Caledonian orogeny to form the Old Red Sandstone paleocontinent of Laurussia. Another example includes a collision that occurred during the late Pennsylvanian and early Permian time when there was a collision between the two continents of Tarimsky and Kirghiz-Kazakh. This collision was caused because of their askew convergence when the paleoceanic basin closed.
