The earth's surface is formed under the influence of numerous external and internal processes that act on it with different speeds and strengths. As a result, it acquires the most diverse and unlike each other forms - from the highest mountain ranges and insignificant hills, to deep faults, depressions and gorges. What is the earth's surface? What structural elements does it include? Let's find out.
Earth's surface
Earth was formed about 4.5 billion years ago, since then its appearance has been constantly changing and transforming. Previously, it was a molten spherical body, but then its upper part solidified, forming a crust with a thickness of 5 to 150 kilometers. It is usually called the earth's surface.
Most of the crust is under water, the rest of it forms the land of the planet in the form of continents and islands. The World Ocean accounts for approximately 70% of the earth's surface. Bark underneathconsists of only two layers, it is much thinner and younger than on land. The bottom of the oceans has the shape of a bed, which gradually descends from the shores of the continents.
Land covers approximately 30% of the planet's surface. Its crust consists of three main layers and reaches an average of 40-45 kilometers in thickness. Large areas of land are called continents. They are unevenly distributed on Earth - 67% of their total area is in the Northern Hemisphere.
The Earth's crust is not continuous and consists of several dozen tightly adjoining tectonic plates. They constantly move relative to each other, shifting every year by 20-100 mm. Weak movements are not felt in everyday life, but strong collisions can be accompanied by earthquakes and other natural disasters. Plate boundaries are a kind of "hot spots" of the planet. Volcanic eruptions, cracks and faults often occur in these places.
Basic forms of the earth's surface
The hard shell of our planet is constantly experiencing the action of internal and external forces. The movement of hot magma and tectonic plates, solar heat, wind, precipitation - all this affects it and creates various irregularities that are inherent in both the continental crust and the seabed.
There are several classifications of types of the earth's surface, in accordance with their characteristics. So, depending on whether they are convex or concave, they are divided into positive or negative. According to the size and scale of the territory they cover, they distinguish:
- Planetary forms - continents,ocean floor, geosynclinal belts and mid-ocean ridges.
- Megaforms - mountains, plains, depressions and plateaus.
- Macroforms - ridges and depressions within the same mountainous country.
- Mesoforms - ravines, river valleys, dune chains and caves.
- Microforms - grottoes, sinkholes, ruts, wells and coastal ramparts.
- Nanoforms - small grooves and bumps, folds and depressions on dunes.
Depending on the processes that influenced their origin, the forms of the earth's surface are divided into:
- tectonic;
- volcanic;
- glacial;
- eolian;
- karst;
- water erosion;
- gravity;
- shore (under the influence of sea waters);
- fluvial;
- anthropogenic, etc.
Mountains
Mountains are highly dissected elevated areas of the planet's surface, the height of which exceeds 500 meters. They are located in areas of increased activity of the earth's crust and are formed as a result of the movement of tectonic plates or volcanic eruptions. Mountain ranges and massifs that are nearby are combined into mountain systems. They occupy 24% of the earth's surface, they are most represented in Asia, least of all in Africa.
Andes-Cordillera is the longest mountain system in the world. It stretches for 18 thousand kilometers, and stretches along the western coasts of South and North America. The highest mountain in the world is the Himalayan Everest, or Chomolungma, with a height of 8850 meters. True, if we consider not absolute, butrelative height, the record holder will be the Hawaiian volcano Mauna Kea. It rises from the bottom of the ocean, from the foot to the top, its height is 10203 meters.
Plains
Plains are vast areas of terrain, the main difference of which is a slight slope, slight dissection of the relief and fluctuations in heights. They occupy about 65% of the earth's surface. They form lowlands at the foot of mountains, valley beds, flat or slightly undulating plateaus and plateaus. They can be formed as a result of the destruction of rocks, flooding and cooling of lava, as well as due to the accumulation of sedimentary deposits. The largest plain on the planet - the Amazonian lowland - covers an area of 5 million km22 and is located in Brazil.
Mountains and plains are one of the most common landforms. Now let's look at the main genetic types of the earth's surface.
Fluvial relief
Water plays a huge geological role, changing and transforming the surrounding landscapes. Permanent and temporary streams destroy rocks in one place and carry it over to another. As a result, two types of relief are formed: denudation and accumulative. The first is associated with the destruction of rocks, its examples are beams, furrows, ravines, canyons, ledges and meanders. The second refers to the accumulation of geological material and manifests itself in the form of deltas, shoals, plumes.
A classic example of a fluvial relief is a river valley. The waters of the newly formed stream flow and make their way, forming channels, floodplains and terraces. The appearance of the river and its valley depends on the strength of the stream and the properties of the rocks below it. So, in soft clay soil, winding and wide watercourses are often formed. Among hard rocks, rivers arise with narrow valleys, which turn into deep gorges and canyons. One of the most beautiful and largest in the world is the Grand Canyon in Colorado, reaching a depth of about 1600 meters.
Eolian relief
Eolian forms of the earth's surface are created by the wind, through the transfer of small particles of dust, clay or light rocks. So, in the deserts, sandy hills appear - dunes, the height of which reaches hundreds of meters. Dunes form along the banks of the rivers, in other places kuchugur, loess and shifting sands appear.
Air currents can not only accumulate, but also destroy. Blowing out small particles, they grind down rocks, which is why corrosion niches, rocks with holes and "stone pillars" are formed. A vivid example of such a phenomenon is the Demerdzhi massif in the Crimea.
Karst terrain
This landform forms where rocks are common that dissolve relatively easily in water. Under the influence of surface or underground sources, various holes, tunnels and galleries appear in deposits of gypsum, s alt, chalk, marble, dolomite, limestone.
Karst forms are represented by caves, funnels, hollows, troughs, karrs, shafts and troughs. They are widedistributed in the world, especially in the Crimea and the Caucasus. This type of relief got its name from the Slovenian Karst plateau, located in the Dinaric Highlands.
Man-made relief
Man also makes a significant contribution to changing the surface of the Earth. During the development of valuable deposits, a huge amount of minerals, soil and mixed rocks are withdrawn from the bowels of the planet. In places of active development, voids and hollows appear in the form of quarries and mines. Tons of unused material pile up separately, forming embankments and dumps.
One of the largest quarries in the world is Bingham Canyon in Utah, USA. It serves for the extraction of copper ore. The deepest wells of the quarry extend 1.2 kilometers down, and its maximum width reaches 4 kilometers. More than 400 tons of rock are mined here annually.
