The Earth's surface is formed under the influence of numerous external and internal processes that act on it with different speeds and forces. As a result, it acquires the most diverse and dissimilar forms - from the highest mountain ranges and minor hills, to deep faults, depressions and gorges. What is the earth's surface? What structural elements does it include? Let's find out.
Earth 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 hardened, 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 planet’s land in the form of continents and islands. On the oceans and accounts for approximately 70% of the earth's surface. Below it, the crust consists 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 decreases 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 not equally distributed on Earth - 67% of their total area is in the Northern Hemisphere.
The crust is not continuous and consists of several tens of closely adjacent tectonic plates. They are constantly moving relative to each other, shifting each 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. The boundaries of the plates are a kind of "hot spots" of the planet. Volcanic eruptions often occur in these places, cracks and faults form.
The main 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 the types of the earth's surface, in accordance with their features. So, depending on whether they are convex or concave, they are divided into positive or negative. The size and scale of the territory they cover, distinguish:
- Planetary forms - continents, ocean bed, geosynclinal belts and mid-ocean ridges.
- Mega-forms - mountains, plains, hollows and plateaus.
- Macroforms are ridges and depressions within the same mountainous country.
- Mesoforms - ravines, river valleys, dune chains and caves.
- Microforms - grottoes, karst funnels, potholes, wells and coastal shafts.
- Nanoforms are small grooves and bumps, folds and indentations 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;
- gravitational;
- coastal (under the influence of sea waters);
- fluvial;
- anthropogenic and others.
The mountains
Mountains are strongly dissected elevated sections 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. The mountain ranges and massifs that are nearby combine into mountain systems. They occupy 24% of the earth’s surface, they are most strongly represented in Asia, least of all - in Africa.
The Andes Cordillera is the longest mountain system in the world. It extends over 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 the absolute, but the relative height, then the record holder will be the Hawaiian volcano Mauna Kea. It grows from the bottom of the ocean, from the foot to the top its height is 10203 meters.
The plains
The plains are vast areas of the terrain, the main difference of which is a slight slope, a slight dissection of the relief and height fluctuations. They occupy about 65% of the earth's surface. They form lowlands at the foot of mountains, a bed of valleys, flat or slightly wavy plateaus and plateaus. They can be formed as a result of the destruction of rocks, the spill 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 km 2 and is located in Brazil.
Mountains and plains are one of the most common landforms. Now let's look at the basic 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 to another in a stream. 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, shallows, plumes.
A classic example of 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 beneath it. So, in soft clay soil often winding and wide streams are formed. Among hard rocks there are rivers 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.
Aeolian relief
Aeolian 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 appear sandy hills - dunes, the height of which reaches hundreds of meters. Dunes form along the banks of rivers; in other places, kuchugurs, loesses, and moving sands appear.
Air currents can not only accumulate, but also destroy. Blowing small particles, they grind away rocks, which leads to the formation of corrosion niches, rocks with holes and "stone pillars". A striking example of this phenomenon is the Demerdzhi massif in the Crimea.
Karst relief
This landform is formed where rocks are common, which are relatively easy to dissolve in water. Under the influence of surface or underground sources in the deposits of gypsum, salt, chalk, marble, dolomite, limestone, various holes, tunnels and galleries appear.
Karst forms are represented by caves, funnels, hollows, gutters, carras, mines and gutters. They are widespread 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.
Technogenic relief
A significant contribution to the change in the Earth’s surface is made by man. During the development of valuable deposits from the bowels of the planet, a huge amount of minerals, soil and mixed rocks are removed. In places of active development, voids and hollows appear in the form of quarries and mines. Tons of unused material are piled separately, forming embankments and dumps.
One of the largest quarries in the world is Bingham Canyon in Utah in the United States. It serves for the extraction of copper ore. The deepest wells in the quarry extend 1.2 kilometers down, and its maximum width reaches 4 kilometers. More than 400 tons of rock are mined annually in it.