A continent is a huge piece of land, where most of it is land. In addition to the land, it includes its outskirts, the shelf and the islands located there. Concepts Continents And Continents in Russian they are synonyms.
A continent is a single, undivided part of land. The largest continent is considered Eurasia, which has two parts of the world: Asia and Europe. Next in size are North America, then South America, after Africa, Australia And Antarctica.
Continents on Earth - 6
Some countries have a different number of continents:
- In China they are sure that there are seven of them, since Asia and Europe are separated into separate parts there.
- In Portugal and Greece, six continents are also distinguished, but instead of uniting Europe and Asia, they unite North and South America.
- The Olympic Committee defines continents as only the inhabited parts of the Earth, excluding Antarctica from this list. That's why there are five continents and the same number of Olympic rings.
If you combine not only Europe and Asia, but also North and South America, you get four continents. Therefore, the dispute over the number of continents has not yet been resolved, scientists different countries put forward their theory and stubbornly prove it. But so far the majority are from six continents on planet Earth.
History of the continents
However, there were not always such a number of continents on Earth. Scientists identify several hypothetical continents that existed on Earth in different time periods.
- Kenorland– a supercontinent that existed during the Neoarchean period (2.75 billion years ago).
- Nuna- a supercontinent whose existence is considered to be the Paleproterozoic era (1.8-1.5 billion years ago).
- Rodinia– supercontinent of the Proterozoic-Precambrian epoch. The continent appeared 1.1 billion years ago and broke up 750 million years ago.
- Pangea- a supercontinent that arose in the Paleozoic (Permian period) and disappeared in the Triassic era (200-210 million years ago).
- Euramerica (or Laurussia)- supercontinent of the Paleozoic era. The continent broke up in the Paleogene era.
- Gondwana- a supercontinent that appeared 750-530 million years ago and broke up 70-80 million years ago.
This is not the entire list of predecessors of modern continents. Moreover, some scientists claim that in the future, earthlings will form another supercontinent. Presumably future events will develop as follows:
- First, Africa will merge with Eurasia.
- In about 60 million years, Australia will connect with Eastern Asia, as a result of which the continent of Australia-Afro-Eurasia will appear.
- In 130 million years, Antarctica will join southern Australia or Asia, and the continent of Australia-Antarctica-Afro-Eurasia will appear.
- In 250-400 million years, the inhabitants of the planet will expect the appearance of the supercontinents Pangea Ultima (200-300 million years, all current continents will merge), Amasia (50-200 million years, the center of the continent will be at the North Pole), Novopangea (re-emergence of the supercontinent past - Pangea).
The information presented is only part of scientists' assumptions about the future of the Earth. And today the erudite and educated people to the question “How many continents are there on Earth?” They confidently answer – exactly 6.
Video
Our planet is the most amazing of all the planets in near and far space.
On its surface there is a unique layer - the hydrosphere. This water shell Earth. It is also found on other planets, but only on ours it is found in three states of aggregation - solid, liquid and gaseous.
In addition to water, there is land on the surface of the Earth - solid areas of the earth's crust. These areas are fragments of the cooling earth's surface. The earth can be compared to an egg - inside it there is a liquid hot mantle, and the earth's crust is just a thin shell.
The Earth's surface is heterogeneous, it has different thicknesses and is broken into “shards” - tectonic plates that move with at different speeds and in different directions. Sometimes they collide and separate. IN different periods existence of the planet, the answer to the question of how many continents there are on Earth was different, and the reason was tectonics.
More than three hundred million years ago there was only one continent - Pangea. under the influence of magmatic vortices, it split into two continents - Laurasia and Gondwana (about 200 million years ago). Only 40 million years ago the surface of the planet acquired the appearance that is familiar to us: now there are six continents on the planet:
- the largest is Eurasia;
- the hottest is Africa;
- the most elongated from north to south is North America;
- South America;
- the coldest is Antarctica;
- the smallest is Australia.
The continents are moving relative to each other and may soon connect again. For example, North America is moving towards Eurasia at a rate of about 20 mm per year.
In addition to continents, the Earth is rich in islands. The largest of them is Greenland. An island belonging to the North American tectonic plate.
More than half of the Earth's surface is covered by water - the World Ocean. On any map you can see that the entire huge body of water represents a single massif. However, science identifies several oceans.
The biota of the ocean depends on physical parameters, therefore both animals and vegetable world will differ in different parts of the World Ocean.
So how to answer the question, how many oceans are there on Earth, using knowledge about the structure of our planet? Most scientists distinguish 4 oceans:
- Pacific Ocean;
- Atlantic Ocean;
- Indian Ocean;
- Arctic Ocean.
Some sources highlight a fifth ocean – the Southern Ocean. It is located in the southern hemisphere of the Earth and washes the shores of Antarctica. Opponents of its isolation believe that this ocean is a place where other oceans meet; water masses in this part do not have time to mix, so they maintain their integrity. In any case, there is no clear definition of the number of oceans yet, but we can confidently say that there are no more than five and no less than four.
In addition to physical parameters, seas differ in size: depth, width of the water surface, coastline. For example, it has been established that the largest sea in the world in terms of surface area is the Sargasso (Atlantic Ocean basin) - an area of 6,000 thousand km 2, and the deepest is the Coral Sea (Pacific Ocean basin), which has a depth of 9,174 meters.
In Russia the most large sea is the Bering Sea (the Arctic Ocean basin) - an area of 2315 thousand km 2.
On the ground? This is best seen when viewed from space. However, not everyone has such an opportunity, so we will limit ourselves to a model of the planet - a globe. If you look at it carefully, you will see that only a third of the Earth is covered by land, and the rest is water. The landmass is divided into several territories called continents. Previously it was believed that there were only five of them: America, Australia, Africa, Europe, Asia.
But today scientists have a different opinion. Firstly, during construction, America was divided into two continents - the Northern and Southern parts. Secondly, Antarctica. Previously, it was believed that the areas around the South Pole were simply huge blocks of ice, but now it is known for certain that this is another continent. True, only penguins live on it, but that doesn’t stop it from being dry land. So we got the answer to the question of how many continents there are on Earth. It turns out there are seven of them.
What are they?
Looking at a map or globe, we can see all the continents that exist on our planet. Let's talk about what they are. Having found out how many continents there are on Earth, let’s clarify - what is it? Continents are huge areas of land washed by oceans and seas.
In scientific terms, a continent (continens) is a large massif, most of which is located above the level of the world ocean and is called land, and the smaller part is located below the designated level and is called peripheral. This concept also includes islands located on the shelf zone of the mainland.
Opinions still differ about how many continents there are on Earth. Their number in different interpretations yours. For example, Europe and Asia - sometimes they are combined into one continent and called Eurasia. As for America, the opposite is true: many consider it one continent, despite the fact that it is divided by a canal into North and South. Based on this, it turns out that everyone has their own approach. That is why scientists have not yet decided how many continents there are on Earth - six or seven.
Now let's look at what each of them is. Asia is the largest continent on Earth. It has an area of 43 million square kilometers. The next huge areas of land are America and Africa. Their areas are respectively 42 and 30 million square meters. km.
But the continent of Australia is the smallest on our planet. It occupies only 8 million sq. km.
It is also very difficult to call Antarctica land, since it is under ice armor. However, despite everything, it is the highest continent on the planet, its height is 2040 meters above sea level. And although there is no permanent population in Antarctica, there are constantly more than 40 research stations from various countries engaged in its study.
According to legend, in ancient times there was another continent - Atlantis. However, scientists have not been able to prove this. It is believed that she was located between America and Europe, but sank as a result of a powerful earthquake. That's how many continents there are on the planet, and each of them has its own climatic conditions, flora and fauna and, of course, population.
MAINLAND
or continent, a large landmass (as opposed to smaller islands) surrounded by water. There are seven parts of the world (Europe, Asia, Africa, North America, South America, Australia and Antarctica) and six continents: Eurasia, Africa, North America, South America, Australia and Antarctica. Some large islands are similar in size to continents and are sometimes called "mainland islands". Among them, the most famous are Greenland, New Guinea, Kalimantan and Madagascar. The continents are surrounded by shallow ocean zones - shelves, with depths usually not exceeding 150 m.
CONTINENTS AND THEIR SIZES
The names of parts of the world and continents have different origins. The ancient Greeks called all the lands to the west of the Bosphorus Europe, and to the east of it Asia. The Romans divided their eastern (Asian) provinces into Asia and Asia Minor (Anatolia). The name "Africa", also of ancient origin, applied only to the northwestern part of the continent and did not include Egypt, Libya and Ethiopia. Ancient geographers theorized that there would be a large continent to the south (Terra Australis - the southern land) that would balance the vast land masses to the north, but this was not discovered until the 17th century. Its original name "New Holland" was later changed to "Australia". By the 18th century include the first guesses about the existence of Antarctica (which means “the antipode of the Arctic”), but the discovery and exploration of this continent dates back only to the 19th-20th centuries. In contrast to Australia, the existence of America was not predicted by anyone, and when it was discovered, it was mistaken for part of China or India. The term "America" first appeared on the map of Martin Waldseemüller (1507), who named it as such New World in honor of the geographer and explorer Amerigo Vespucci. Vespucci was probably the first to realize that a new continent had been discovered. The term "mainland" itself in its modern meaning appeared in England in the 17th century. The continents account for 94% of the land area and 29% of the planet's surface area. However, not the entire area of the continents is land, since there are large inland seas (for example, the Caspian), lakes and areas covered with ice (especially in Antarctica and Greenland). Continental boundaries have often been the subject of controversy. Residents of Great Britain, for example, traditionally separated their island state from the mainland of Europe, which, in their opinion, began from Calais. The boundaries of parts of the world and continents have always caused headaches for geographers. Europe and Asia are separated by a watershed Ural mountains , but to the south the border becomes less clear and is again defined only in the Greater Caucasus. Further, the border runs along the Bosphorus, dividing Turkey into the European part (Thrace) and the Asian part (Anatolia, or Asia Minor). A similar problem arises in Egypt: the Sinai Peninsula is often classified as Asia. From a geographical point of view, all of Central America, including Panama, is usually added to North America, but politically it is often practiced to include all territories located south of the USA
, to Latin America.
STRUCTURAL GEOLOGY
The word "continent" comes from the Latin continens (continere - to stick together), which implies structural unity, although not necessarily in relation to land. With the development of the theory of lithospheric plate tectonics in geology, a geophysical definition of continental plates as opposed to oceanic plates arose. These structural units have completely different structure, power and development history. Continental crust, made up of rocks that are predominantly silicon (Si) and aluminum (Al), is lighter and much older (some areas are over 4 billion years old) than oceanic crust, which is made up mostly of silicon (Si). and magnesium (Mg) and is no more than 200 million years old. The boundary between the continental and oceanic crust runs along the foot of the continental slope or along the outer limit of the shallow shelf that borders each continent. The shelf adds 18% to the area of the continents. This geophysical definition emphasizes the well-known differences between such “mainland islands” as the British, Newfoundland and Madagascar, from the oceanic ones - Bermuda, Hawaii and Guam. During the long evolution of the Earth's crust, the continents gradually expanded due to the accumulation of lava and ash from volcanic eruptions, the intrusion of molten magma from rocks such as granite, and the accumulation of sediments originally deposited in the ocean. The constant fragmentation of ancient land masses - the "proto-continents" - predetermined the drift of the continents, as a result of which they periodically collided. Ancient continental plates were firmly connected along these contact lines, or “seams,” forming a complex mosaic (“patchwork”) of structural units that make up modern continents. In the east North America such a suture zone can be traced from Newfoundland to Alabama. Fossils found in rocks to the east of it are of African origin, which is evidence of the separation of this area from the African continent that occurred (about 300 million years ago). Another suture zone, marking the collision of Europe with Africa approximately 100 million years ago, can be traced in the Alps. Another suture runs along the southern border of Tibet, where the Indian subcontinent collided with the Asian subcontinent and in geologically recent times (about 50 million years ago) the Himalaya mountain system was formed.
The theory of lithospheric plate tectonics today is as generally accepted in geology as, for example, the law universal gravity in physics. "African-type" rocks and fossils have been found in many places in the eastern Americas. The suture zones are clearly visible in satellite images. The speed of upward movements can be measured where mountains, resulting from the collision of continents, still continue to rise. These speeds do not exceed 1 mm per year in the Alps, and in separate parts The Himalayas are more than 10 mm per year. The logical consequence of the considered mechanism of mountain building is continental rifting and spreading of the ocean floor. Fragmentation of the earth's crust is a widespread phenomenon, clearly visible in satellite images. The main fault lines, called lineaments, can be traced both in space - thousands of kilometers, and in time - to the most ancient stages of geological history. When both sides of the lineament are strongly displaced, a fault is formed. The origin of the largest faults has not yet been fully established. A computer model of a network of faults suggests that their formation is associated with changes in the shape of the globe in the past, which, in turn, was predetermined by fluctuations in the speed of rotation of the Earth and changes in the position of its poles. These changes were caused by a number of processes, among which the most significant influence was exerted by ancient glaciations and the bombardment of the Earth by meteorites. Ice ages repeated approximately every 250 million years and were accompanied by the accumulation of significant masses glacial ice near the poles. This accumulation of ice caused an increase in the speed of rotation of the Earth, leading to a flattening of its shape. At the same time, the equatorial belt expanded in diameter, and the spheroid seemed to shrink at the poles (i.e., the Earth became less and less like a ball). Due to the fragility of the earth's crust, a network of intersecting faults has formed. The speed of the Earth's rotation changed dozens of times during one ice age. On early stages During the history of the Earth, the planet was intensively bombarded by asteroids and smaller objects - meteorites. It was uneven and, apparently, led to a deviation of the axis of rotation and a change in its speed. The scars from these impacts and the craters left by the "celestial guests" are visible everywhere on the lower planets (Mercury and Venus), although on the earth's surface they are partially masked by sediment, water and ice. These bombardments also contributed to the chemical composition of the continental crust. Because falling objects tended to concentrate near the equator, they added mass to the outer edge of the globe, significantly slowing its rotation rate. In addition, throughout geological history, any powerful outpourings of volcanic lava in one of the hemispheres or any mass movements contributed to a change in the inclination of the axis of rotation and the speed of rotation of the Earth. It has been established that lineaments are weakened zones of the continental crust. The earth's crust can bend like window glass under the pressure of gusts of wind. All of it is actually cut by faults. Along these zones, minor movements occur all the time, caused by the tidal forces of the Moon. As the plate moves toward the equator, it comes under increasing stress, both due to tidal forces and changes in the Earth's rotation rate. These stresses are most pronounced in the central parts of the continents, where rifting occurs. Zones of young rifting occur in North America from the Snake River to the Rio Grande River, in Africa and the Middle East - from the Jordan River Valley to Lakes Tanganyika and Nyasa (Malawi). In the central regions of Asia there is also a rift system passing through Lake Baikal. As a result of long-term processes of rifting, continental drift and their collisions, the continental crust was formed in the form of a “patchwork quilt”, consisting of fragments of different ages. It is interesting to note that on every continent at the present time rocks of all geological epochs seem to be represented. The basis of the continents is the so-called. shields composed of ancient strong crystalline rocks (mainly granite and metamorphic series), which belong to various Precambrian eras (i.e. their age exceeds 560 million years). In North America, such an ancient core is the Canadian Shield. At least 75% of the continental crust was formed 2.5 billion years ago. Areas of shields covered by sedimentary rocks are called platforms. They are characterized by flat, flat terrain or gently undulating arched hills and basins. When drilling for oil beneath sedimentary rocks, crystalline basement is sometimes exposed. Platforms are always an extension of ancient shields. In general, this core of the continent - the shield together with the platform - is called the craton (from the Greek krtos - strength, fortress). Fragments of young folded mountain belts are attached to the edges of the craton, usually including small cores (“fragments”) of other continents. Thus, in North America, in the eastern Appalachians, “shards” of African origin are found. These young components of each continent provide clues to the history of the ancient shield and, apparently, develop in much the same way as itself. In the past, the shield also consisted of mountain belts, which are now leveled to almost flat or only moderately dissected relief by erosion. A similar leveled surface, called peneplain, is the result of erosion-denudation processes that occurred more than half a billion years ago. Basically, these leveling processes took place under conditions of tropical crust formation. Since the main agent of such processes is chemical weathering, the result is the formation of a sculptural plain. In the modern era, only bedrock remains on the shields, remaining after rivers and glaciers destroyed and carried away ancient loose sediments. In younger mountain belts, uplifts were often repeated along the edges of cratons, but there was not enough time for the formation of peneplain, so a series of stepped erosion surfaces formed instead.
Continental rifting. The most impressive result of young rifting is the Red Sea rift between the Arabian Peninsula and Northeast Africa. The formation of this rift began ca. 30 million years ago and is still happening. The opening of the Red Sea depression continues to the south in the East African Rift Zone and to the north in the Dead Sea and Jordan Valley areas. The biblical story of the collapse of the walls of Jericho is probably based on fact, since this ancient city is located within the main discharge zone. The Red Sea represents the "young ocean". Although its width is only 100-160 km, its depth is separate areas comparable to oceanic ones, but what is most remarkable is that there are no remains of continental crust there. Previously, it was believed that a rift was similar to a destroyed arch with a fallen top (“key”) stone. Numerous studies have not confirmed this assumption. It has been established that the two edges of the rift seem to be moved apart, and the bottom consists of hardened “oceanic” lava, which is currently largely covered by young sediments. This is the beginning of seafloor spreading, a geological process that results in the formation of oceanic-type crust (Ocean floor spreading is considered as strong evidence in favor of the theory of plate tectonics.) All deep oceans have this type of crust, and only shallow seas like the Hudson or Persian Gulf, are underlain by continental crust. At the beginning of the development of the theory of plate tectonics, the question was often asked: if continental rifts and ocean floors expand during spreading, should not they themselves Earth expand accordingly? The mystery was solved when subduction zones were discovered - planes inclined at approximately 45°, along which oceanic crust is pushed under the edge of the continental plate. At a depth of approx. 500-800 km from the Earth's surface, the crust melts and rises again, forming magma chambers - reservoirs of lava, which then erupts from volcanoes.
Volcanoes. The locations of volcanoes are closely related to the movement of lithospheric plates, and three types of volcanic zones are distinguished. Subduction zone volcanoes form the Pacific Ring of Fire, the Indonesian Arc, and the Antilles Arc in the West Indies. Such volcanoes of subduction zones are known as Fuji in Japan, St. Helens and others in the Cascade Mountains of the USA, Montagne Pelee in the West Indies. Inland volcanoes are often confined to fault or rift zones. They are found in the Rocky Mountains from Yellowstone National Park and the Snake River to the Rio Grande River, as well as in East Africa (for example, Mount Kenya and Mount Kilimanjaro). Volcanoes of mid-ocean fault zones are found on the oceanic islands of Hawaii, Tahiti, Iceland, etc. Both inland and mid-ocean volcanoes (at least the largest of them) are associated with deep-lying “hot spots” (rising convective jets) in the mantle. As the overlying plate shifts, a chain of volcanic centers appears, arranged in chronological order. These three types of volcanoes differ in the nature of volcanic activity, the chemical composition of the lava and the history of development. Only lava from subduction zone volcanoes contains large volumes of dissolved gases, which can lead to catastrophic explosions. Other types of volcanoes can hardly be called "friendly", but they are much less dangerous. Note that only the most general classification of eruptions is possible, since the activity of the same volcano proceeds differently each time and even individual phases of one eruption may differ.
The surface of the continents. The relief features of the continents are studied by the science of geomorphology (geo is a derivative of the name of the Greek goddess of the Earth Gaia, morphology is the science of forms). Landforms can be of any size: from large ones, including mountain systems (such as the Himalayas), giant river basins (Amazon), deserts (Sahara); to small ones - sea beaches, cliffs, hills, streams, etc. Each relief form can be analyzed from the point of view of structural features, material composition and development. It is also possible to consider dynamic processes, which mean physical mechanisms that caused changes in relief shapes over time, i.e. predetermined the modern appearance of the relief. Almost all geomorphological processes depend on the following factors: the nature of the source material (substrate), structural position and tectonic activity, as well as climate. The largest landforms include mountain systems, plateaus, depressions and plains. Mountain systems have undergone crushing and compression during the movement of plates, and erosion-denudation processes currently prevail there. The land surface is gradually destroyed by frost, ice, rivers, landslides and wind, and the products of destruction accumulate in depressions and plains. Structurally, mountains and plateaus are characterized by ongoing uplifts (from the point of view of the theory of plate tectonics, this means heating of deep layers), while depressions and plains are characterized by weak subsidence (due to cooling of deep layers).
There is a compensation process, the so-called. isostasy, one of the results of which is that as mountains are destroyed by erosion processes, they experience uplift, and on the plains and in depressions where sediment accumulates, there is a tendency to sink. Under the earth's crust is the asthenosphere, consisting of molten rocks, on the surface of which lithospheric plates "float". If any part of the earth's crust is overloaded, it will "sink" (sink into molten rock), while the rest of it will "float" (rise). The main reason for the uplift of mountains and plateaus is plate tectonics, but erosion-denudation processes in combination with isostasy contribute to the periodic rejuvenation of ancient mountain systems. Plateaus are similar to mountains, but they are not crushed as a result of collision (collision of plates), but are raised as a single block and are usually characterized by horizontal occurrence of sedimentary rocks (as, for example, is clearly visible in the outcrops of the Grand Canyon in Colorado). Another geological process that plays a very important role in the long history of continents, eustasy, reflects global fluctuations in sea level. There are three types of eustasy. Tectonic eustasy is caused by changes in the shape of the seafloor. During rapid subduction, the width of the ocean basin shrinks and sea levels rise. The ocean basin is also becoming shallower due to thermal expansion oceanic crust during a sudden acceleration of seafloor spreading. Sedimentary eustasy is caused by the filling of the ocean basin with sediments and lava. Glacioeustasy is associated with the removal of water from the oceans during continental glaciations and its release during the subsequent global melting of glaciers. During periods of maximum glaciation, the area of continents increased by almost 18%. Of the three types considered, glacioeustasy played the most important role in human history. On the other hand, the effect of tectonic eustasy was the most long-lasting. Periodically, the level of the World Ocean rose, and as a result, large parts of the continents were flooded. The exception was the mountains. These global floods are called "thalassocratic" (from the Greek thlassa sea and krtos - strength, power) phases of the Earth's development. The last such flood occurred ca. 100 million years ago, during the era of dinosaurs (some living organisms of that time preferred an aquatic lifestyle). Marine sediments of that time with characteristic fossil organisms discovered in inland areas indicate that North America from the Gulf of Mexico to the Arctic was flooded by the sea. Africa was divided into two parts by a shallow strait crossing the Sahara. Thus, each continent was reduced to the size of a large archipelago. Completely different conditions existed in eras when the ocean floor sank. The sea retreated from the shelves, and the land expanded everywhere. Such eras are called “epeirocratic” (from the Greek peiros - continent, land). The alternation of epeirocratic and thalassocratic phases determined the main course of geological history and left traces in the main features of the relief of each continent. These phenomena also had a great impact on the animal and plant world. The course of evolution of both the physical and biological world was also determined by changes in the area of the oceans. During the thalassocratic phases, an oceanic climate was formed with moisture-saturated air masses penetrating onto the land. As a result, the average temperature on Earth was at least 5.5°C higher than today. Glaciers existed only in very high mountains. Conditions on all continents were more or less uniform, the land was covered with lush vegetation, which contributed to the development of soils. However, land animals experienced severe stress due to overpopulation and separation, unlike their marine counterparts, who flourished in the vast expanses of significantly increased shelves. During the epeirocratic phases, the opposite situation developed. The area of the continents increased, and new habitats were ideal for the existence of large animals such as dinosaurs. The largest land area occupied approx. 200 million years ago, which favored the evolution of these creatures. In the climatic conditions of that time, with a high “continentality index,” deserts and red sediments were widespread and mechanical erosion predominated. Modern relief is closely dependent on geological history. The appearance of the Alps or Himalayas indicates a young uplift: these mountains are typical collision structures. The Great Interior Plains of North America and northern Eurasia are overlain by predominantly subhorizontal sedimentary formations that were deposited during repeated global marine transgressions throughout geological history. In turn, they are covered by a thin moraine cover (sediments from glacial periods) and loess (products of activity especially strong winds, usually blowing in the direction from large ice sheets to their periphery). It is interesting to note that the plains of the Northern and Southern Hemispheres look completely different. In Brazil, South Africa and Australia are invariably amazed by exotic landforms. Modern era represents an epeirocratic phase in the history of the Earth with increasing differentiation of individual continents and increasing climatic contrasts. But why is there a difference between the northern and southern continents? The answer to this question is provided by plate tectonics. All northern continents were moved apart over considerable distances and over the past almost 200 million years have slowly moved northward. As a result of this drift, they moved from tropical and subtropical latitudes to temperate and arctic ones. From those distant times, red-colored soils, typical of hot, dry climate conditions, were inherited, and many existing landforms could not have formed under modern climatic conditions. In the recent geological past, vast areas of these continents were covered with glaciers. The history of the development of the southern continents was completely different. They experienced the last glaciation 250 million years ago, being part of the pre-existing continent of Gondwana. Since then, they have gradually shifted north (i.e. towards the modern equator), so that many modern forms The topography in these regions is inherited from colder climatic conditions. The Northern Hemisphere has 48% more land area than the Southern Hemisphere. This distribution has a profound impact on the climate, causing greater continentality in the north and greater oceanicity in the south.
Rates of erosion-denudation processes. Research has shown that in many regions of the world there are ancient land areas - cratons, which are outcrops composed of ancient sedimentary formations, which are often cemented with the bedrock by silica and form strong, quartz-like covers. This cementation occurred during the formation of sculpted plains in tropical and subtropical environments. Once formed, such a shell, armoring the terrain, could then exist without change for millions of years. In mountainous regions, rivers cut through this durable cover, but fragments of it are often preserved. Subhorizontal watersheds in the Appalachians, Ardennes, and Urals represent remnants of pre-existing sculpted plains. Based on the age of such ancient residual formations, the average rate of denudation over a long time interval was calculated to be ca. 10 cm per million years. The surfaces of the Earth's ancient cratons have absolute heights of 250-300 m, so to cut them down to modern level sea, it would take approx. 3 billion years.
LITERATURE
Le Pichon K., Franshto J., Bonnin J. Plate tectonics. M., 1977 Leontiev O.K., Rychagov G.I. General geomorphology. M., 1979 Ushakov S. A., Yasamanov N. A. Continental drift and climates of the Earth. M., 1984 Khain V. E., Mikhailov A. E. General geotectonics. M., 1985
Collier's Encyclopedia. - Open Society. 2000 .
It is not enough just to know what a globe is. You need to learn how to read it correctly in order to learn a lot of new and interesting things. In this lesson we will learn what the colors on the globe mean. Let's learn the names of the oceans and continents, talk about their features and differences. Let's get acquainted with the amazing wonders of nature, flora and fauna.
Why are there the most blue and cyan colors on the globe? Most of the earth's surface is covered with water. In a photograph taken from space, all areas of water appear blue. This color on the globe indicates oceans and seas, rivers and lakes.
Rice. 2. Earth from space ()
But if you look closely, you will notice that in different places the ocean is indicated by different shades. This is done to show depth: the deeper the ocean, the darker the blue color, and the shallower the depth, the lighter the paint on the globe.
- these are huge expanses of bitterly salty water that surround continents and islands. Pacific Ocean
- the largest on Earth.
Rice. 4. Physical map of the Pacific Ocean () This name was given to him by the navigator Ferdinand Magellan, because during his journey to sailing ships this ocean was calm. Although in fact the Pacific Ocean is not quiet at all, especially in its western part, where it raises and drives - huge waves tsunami
, bringing a lot of trouble to the inhabitants of the Japanese islands. Mariana Trench
- the deepest place in the world. It is located in the Pacific Ocean, its depth is eleven kilometers and thirty-four meters.
Rice. 6. Mariana Trench () Previously, Europeans did not even suspect the existence of the Pacific Ocean. They knew only one ocean - Atlantic , which seemed limitless, so it was named after the strong hero
Greek myths Atlanta.
Rice. 7. Physical map of the Atlantic Ocean ()
In fact, the Atlantic Ocean is the second largest after the Pacific Ocean, the greatest depth of the ocean is 5 kilometers. In the Atlantic Ocean there are huge waves as high as a three-story house. Indian Ocean
It is especially restless in its southern part. It is warmer than others; even in the northern part of the Indian Ocean, the waters warm up to + 35 degrees.
Rice. 8. Physical map of the Indian Ocean ()- the northernmost region, covered in winter and summer with a thick layer of ice and snow. There is a fourth ocean near the North Pole, almost its entire surface is covered with thick strong ice, and there are multi-meter snowdrifts around. That's why this ocean was named Arctic.
Rice. 9. Physical map of the Arctic Ocean
Relatively recently, oceanographers began to identify a fifth, South ocean.
Rice. 10. Physical map of Antarctica ()
Previously, this ocean was considered to be the southern parts of the Indian, Atlantic and Pacific oceans. All oceans together: Pacific, Indian, Atlantic, Arctic and Southern - merge together into one world Ocean, which washes the entire globe.
On the globe, large areas of land called continents are depicted in green, yellow, brown and white. On the ground six continents: Eurasia, Africa, Australia, Antarctica, North America, South America.
Eurasia- the largest continent, within its borders lie two parts of the world: Europe and Asia.
Rice. 11. Physical map of Eurasia ()
It is the only continent on Earth washed by four oceans: the Arctic in the north, the Indian in the south, the Atlantic in the west and the Pacific in the east. Our homeland is located on this continent Russia.
Rice. 12. Russia on the map of Eurasia ()
The surface of the continent is very diverse. Mountains and plains are the main forms of the earth's surface. Brown color indicates the location of the mountains, and green and yellow indicate the location of the plains. The largest of them West Siberian(flat plain) Eastern European(hilly plain).
Rice. 13. West Siberian Plain ()
Rice. 14. Physical map of the East European Plain ()
Rivers are indicated on the globe by uneven blue lines drawn along the surface of the continents. Rivers flow across the East European Plain Volga, Don, Dnieper, a river flows across the West Siberian Plain Ob. Mountains rise above the surface of the plains. The higher the mountains, the darker their color on the globe. Himalayas are the highest mountains in the world.
Rice. 15. Himalaya mountains ()
Jamalungma (Everest)- the highest mountain in the world (8 km 708 m).
Rice. 16. Mount Jamalungma ()
Located in Eurasia Baikal- the deepest lake,
Rice. 17. Lake Baikal ()
The largest lake
Rice. 18. Caspian Sea ()
largest peninsula Arabian,
Rice. 19. Coast of the Arabian Peninsula ()
lowest point of land in the world - depression Dead Sea.
Rice. 20. Dead Sea ()
Rice. 21. Pole of Cold Oymyakon ()
Africa is the second largest continent, which is located on both sides of the equator, washed by the Atlantic Ocean from the west and the Indian Ocean from the east and south.
Rice. 22. Physical map of Africa ()
Africa is known for its diversity of nature: impenetrable tropical forests with orchids,
Rice. 23. Rainforest ()
grassy plains with baobabs (huge trees up to forty meters in circumference),
vast expanses of desert.
Rice. 25. Desert in Africa ()
Africa is the hottest continent on the planet. Here it is Sahara Desert.
Rice. 26. Sahara Desert ()
It is the largest desert in the world and the hottest place on Earth (the maximum recorded temperature is +58 degrees). On this continent flows Nile- the second longest river in the world.
Rice. 27. River Nile ()
Volcano Kilimanjaro- the highest point in Africa.
Rice. 28. Mount Kilimanjaro ()
Victoria, Tanganyika, Chad- the largest lakes on this continent.
Rice. 29. Lake Victoria ()
Rice. 30. Lake Tanganyika ()
Rice. 31. Lake Chad ()
In the Western Hemisphere are North America And South America, they are washed from the west by the Pacific Ocean, from the east by the Atlantic, and North America is also washed by the Arctic Ocean from the north.
Rice. 32. Physical map of North America
Rice. 33. Physical map of South America
North America also includes the most large island on Earth, it's called Greenland.
Rice. 34. Coast of Greenland ()
These continents are rich in rivers and lakes. In North America there is one of the greatest rivers peace Mississippi,
Rice. 35. Mississippi River ()
and in South America there is a river that is the largest in the world in terms of depth and length.
Rice. 36. Amazon ()
There is a bay on the coast of North America Fundy, which, in addition to his incredible beauty, famous for the largest tides in the world, more than seventeen meters.
Rice. 37. Bay of Fundy ()
Just imagine, millions of tons of water approach the shore in twelve hours and then move away from it. South America is home to the world's tallest waterfall - Angel, its total height is 979 meters.
Rice. 38. Angel Falls ()
It seems as if it is shrouded in fog - a curtain of tiny particles of water that sprays, falling from such a great height. The most powerful waterfall in the world is located on the same continent Iguazu.
Rice. 39. Iguazu Falls ()
Although in fact it is a whole complex of 270 individual waterfalls, which is about 2.7 km wide. South America is home to the driest place in the world - the desert. Atacama.
Rice. 40. Atacama Desert ()
In some places in this desert, rain falls once every few decades.
Australia- the fifth continent, which is smaller than all the others. The Pacific Ocean washes the northern and eastern coasts, the Indian Ocean washes the western and southern coasts.
Rice. 41. Physical map of Australia
Most of the continent is occupied by deserts and semi-deserts, there are very few rivers, which is why Australia is considered the driest continent on Earth. Common here screams(English creek - rivulet) - rivers that exist only during the rainy season and completely dry up for most of the year.
