Various forms reliefs are formed under the influence of processes, which can be predominantly internal or external.
Internal (endogenous)- these are processes inside the Earth, in the mantle, the core, which manifest themselves on the surface of the Earth as destructive and creative. Internal processes create, first of all, large landforms on the surface of the Earth and determine the distribution of land and sea, the height of mountains, and the sharpness of their outlines. The result of their action is deep faults, deep folds, etc.
tectonic(the Greek word "tectonics" means construction, building art) movements earth's crust called the movement of matter under the influence of processes occurring in the deeper bowels of the Earth. As a result of these movements, the main unevenness of the relief on the surface of the Earth arises. The zone of manifestation of tectonic movements, which extends to a depth of about 700 km, is called tectonosphere.
Tectonic movements have their roots in the upper mantle, since the cause of deep tectonic movements is the interaction of the earth's crust with the upper mantle. Their driving force is magma. The flow of magma periodically rushing to the surface from the bowels of the planet provides a process called magmatism.
As a result of solidification of magma at a depth (intrusive magmatism), intrusive bodies (Fig. 1) appear - sheet intrusions (from lat. intrude- I push), dikes (from the English. dike, or dyke, literally - a barrier, a wall of stone), batholiths (from the Greek. bathos- depth and lithos- stone), rods (German. Stock, literally - stick, trunk), laccoliths (Greek. lakkos- hole, hole and lithos- stone), etc.
Rice. 1. Shapes of intrusive and effusive bodies. Intrusions: I, batholith; 2 - stock; 3 - laccolith; 4 - lopolit; 5 - dike; 6 - sill; 7 - vein; 8 - paophysis. Effusives: 9 - lava flow; 10 - lava cover; 11 - dome; 12- neck
Reservoir intrusion - a layer-like body of magma solidified at a depth, having the form of a layer, the contacts of which are parallel to the layering of the host rocks.
Dikes - lamellar, clearly bounded by parallel walls of the body of intrusive igneous rocks, which penetrate the rocks sweeping them (or lie unconformably with them).
Batholith - a large massif of magma frozen at depth, having an area measured in tens of thousands of square kilometers. The shape in plan is usually elongated or isometric (has approximately equal dimensions in height, width and thickness).
stock - an intrusive body shaped like a column in vertical section. In terms of its shape is isometric, irregular. They differ from batholiths in smaller sizes.
Laccoliths - have a mushroom-shaped or dome-shaped upper surface and a relatively flat lower surface. They are formed by viscous magmas that enter either through dike-like supply channels from below or from the sill, and, propagating along the bedding, raise the host overlying rocks without disturbing their bedding. Laccoliths occur singly or in groups. Laccoliths are relatively small in size, ranging from hundreds of meters to several kilometers in diameter.
Magma solidified on the surface of the Earth forms lava flows and covers. This is an effusive type of magmatism. Modern effusive magmatism is called volcanism.
Magmatism is also associated with the occurrence earthquakes.
crustal platform
Platform(from the French plat- flat and form- form) - a large (several thousand km across), relatively stable part of the earth's crust, characterized by a very low degree of seismicity.
The platform has a two-story structure (Fig. 2). lower floor - foundation- this is an ancient geosynclinal region - formed by metamorphosed rocks, the upper - case - marine sedimentary deposits of small thickness, which indicates a small amplitude of oscillatory movements.
Rice. 2. Platform structure
Age of platforms different and determined by the time of formation of the foundation. The most ancient are platforms, the foundation of which is formed by Precambrian crystalline rocks crumpled into folds. There are ten such platforms on Earth (Fig. 3).
The surface of the Precambrian crystalline basement is very uneven. In some places, it comes to the surface or lies near it, forming shields, in others - anteclises(from Greek. anti- against and klisis- inclination) and syneclises(from Greek. syn- together, klisis- mood). However, these irregularities are covered by sedimentary deposits with a calm, close to horizontal occurrence. Sedimentary rocks can be collected into gentle swells, dome-shaped uplifts, stepped bends, and sometimes faults with vertical mixing of layers are also observed. Disturbances in the occurrence of sedimentary rocks are due to the unequal speed and different signs of the oscillatory movements of the blocks of the crystalline basement.
Rice. 3. Pre-Cambrian platforms: I - North American; II - East European; III - Siberian; IV - South American; V - African-Arabian; VI - Indian; VII - East China; VIII - South China; IX - Australian; X - Antarctic
The foundation of younger platforms is formed during periods Baikal,Caledonian or Hercynian folding. Areas of Mesozoic folding are not usually called platforms, although they are such at a relatively early stage of development.
In the relief, the platforms correspond to plains. However, some platforms have experienced major restructuring, expressed in general uplift, deep faults, and large vertical movements of blocks relative to each other. This is how folded-block mountains arose, an example of which is the Tien Shan mountains, where the revival of the mountainous relief occurred during the Alpine orogeny.
Throughout geological history in the continental crust there was an increase in the area of platforms and a reduction in geosynclinal zones.
External (exogenous) processes caused by solar radiation reaching the earth. Exogenous processes smooth out irregularities, level surfaces, and fill depressions. They appear on earth's surface both destructive and constructive.
Destructive processes - this is the destruction of rocks, which occurs due to temperature differences, the action of wind, erosion by streams of water, moving glaciers. Creative the processes are manifested in the accumulation of particles carried by water and wind in land depressions, at the bottom of reservoirs.
The most difficult external factor is weathering.
Weathering- a set of natural processes leading to the destruction of rocks.
Weathering is conditionally divided into physical and chemical.
Main reasons physical weathering are temperature fluctuations associated with daily and seasonal changes. As a result of temperature fluctuations, cracks form. Water that enters them, freezing and thawing, expands the cracks. This is how the rock ledges are leveled, screes appear.
The most important factor chemical weathering also is water and the chemical compounds dissolved in it. At the same time, a significant role is played by climatic conditions and living organisms whose waste products affect the composition and dissolving properties of water. The root system of plants also has great destructive power.
The weathering process leads to the formation of loose products of destruction of rocks, which are called weathering crust. It is on it that the soil is gradually formed.
Due to weathering, the surface of the Earth is constantly being updated, the traces of the past are being erased. At the same time, external processes create landforms due to the activity of rivers, glaciers, and wind. All of them form specific landforms - river valleys, ravines, glacial forms, etc.
Ancient glaciations and landforms formed by glaciers
Traces of the most ancient glaciation were found in North America in the Great Lakes region, and then in South America and in India. The age of these glacial deposits is about 2 billion years.
Traces of the second - Proterozoic - glaciation (15,000 million years ago) have been identified in Equatorial and South Africa and in Australia.
At the end of the Proterozoic (650-620 million years ago), the third, most grandiose glaciation took place - Doxmbrian, or Scandinavian. Traces of it are found on almost all continents.
There are several hypotheses about the causes of glaciation. The factors underlying these hypotheses can be divided into astronomical and geological.
To astronomical factors that cause cooling on Earth are:
- change in the tilt of the earth's axis;
- deviation of the Earth from its orbit towards the distance from the Sun;
- uneven thermal radiation from the sun.
To geological factors include the processes of mountain building, volcanic activity, the movement of continents.
According to the continental drift hypothesis, huge areas of land during the history of the development of the earth's crust periodically moved from a warm climate to a cold climate, and vice versa.
The intensification of volcanic activity, according to some scientists, also leads to climate change: some believe that this leads to a warming of the climate on Earth, while others - to a cooling.
Glaciers have a significant impact on the underlying surface. They smooth out uneven terrain and demolish rock fragments, and widen river valleys. And besides, glaciers create specific landforms.
There are two types of relief that have arisen due to the activity of the glacier: created by glacial erosion (from lat. erosio- corrosion, destruction) (Fig. 4) and accumulative (from lat. accumulatio— accumulation) (Fig. 5).
Glacial erosion created troughs, karts, circuses, carlings, hanging valleys, "ram's foreheads", etc.
Large ancient glaciers carrying large rock fragments were powerful rock destroyers. They widened the bottoms of the river valleys and steepened the sides of the valleys along which they moved. As a result of such activity of ancient glaciers, trogs or trough valleys - valleys with a U-shaped profile.
Rice. 4. Landforms created by glacial erosion
Rice. 5. Accumulative forms of glacial relief
As a result of the splitting of rocks by water freezing in cracks and the removal of the resulting fragments by glaciers sliding down, arose punishment- bowl-shaped recesses of an armchair shape in the near-top part of the mountains with steep rocky slopes and a gently concave bottom.
A large developed car with access to the underlying trough was called glacial circus. It is located in upper parts troughs in the mountains, where large valley glaciers have ever existed. Many circuses have steep sides several tens of meters high. The bottoms of cirques are characterized by lake basins worked out by glaciers.
Peaked forms formed during the development of three or more carinas different sides from one mountain, are called carlings. Often they have a regular pyramidal shape.
In places where large valley glaciers received small tributary glaciers, hanging valleys.
"Sheep foreheads" - these are small rounded hills and uplands, composed of dense bedrock, which have been well polished by glaciers. Their slopes are asymmetrical: the slope facing down the glacier movement is slightly steeper. Often on the surface of these forms there is glacial shading, and the streaks are oriented in the direction of glacier movement.
The accumulative forms of glacial relief include moraine hills and ridges, eskers, drumlins, sandrs, etc. (see Fig. 5).
Moraine ridges - rampart-like accumulations of products of destruction of rocks deposited by glaciers, up to several tens of meters high, up to several kilometers wide and, in most cases, many kilometers long.
Often the edge of the sheet glacier was not even, but was divided into quite distinctly distinct lobes. Probably, during the deposition of these moraines, the edge of the glacier was almost in a stationary (stationary) state for a long time. At the same time, not one ridge was formed, but a whole complex of ridges, hills and basins.
Drumlins- elongated hills, shaped like a spoon, turned upside down with a convex side up. These forms are composed of deposited moraine material and in some (but not all) cases have a bedrock core. Drumlins are usually found in large groups - several dozen or even hundreds. Most of these landforms are 900-2000 m long, 180-460 m wide and 15-45 m high. Boulders on their surface are often oriented with long axes in the direction of ice movement, which was carried out from a steep slope to a gentle one. Apparently, drumlins were formed when the lower layers of ice lost their mobility due to overloading with clastic material and were overlapped by moving upper layers, which processed the material of the deposited moraine and created the characteristic forms of drumlins. Such forms are widespread in the landscapes of the main moraines in the regions of the ice cover.
Zandrovyeplains composed of material brought by flows of melted glacial waters, and usually adjoin the outer edge of the terminal moraines. These coarsely graded deposits consist of sand, pebbles, clay, and boulders ( maximum size which depended on the transport capacity of the flows).
Oz - these are long narrow winding ridges, composed mainly of sorted deposits (sand, gravel, pebbles, etc.), ranging in length from several meters to several kilometers and up to 45 m high. in the body of the glacier.
Kamy - these are small steep hills and short ridges irregular shape composed of sorted sediments. This form of relief can be formed both by glacial water flows and simply by flowing water.
perennial, or eternal Frost- strata of frozen rocks that do not thaw for a long time - from several years to tens and hundreds of thousands of years. Permafrost affects the relief, since water and ice have different densities, as a result of which freezing and thawing rocks are subject to deformation.
Most common type of deformity frozen ground- heaving associated with an increase in the volume of water when freezing. The resulting positive landforms are called swelling bumps. Their height is usually no more than 2 m. If heaving mounds formed within the peaty tundra, then they are usually called peat mounds.
Summer upper layer permafrost thaws. The underlying permafrost prevents meltwater from seeping down; water, if it does not find a runoff into a river or lake, remains in place until autumn, when it freezes again. As a result, melt water is between a waterproof layer of permafrost from below and a layer of new seasonal permafrost gradually growing from top to bottom. LSD takes up more space than water. Water, being between two layers of ice under enormous pressure, looks for a way out in the seasonally frozen layer and breaks through it. If it pours onto the surface, an ice field is formed - frost. If there is a dense moss-grass cover or a layer of peat on the surface, the water may not break through it, but only lift it up,
spreading across it. Freezing then, it forms the icy core of the mound; gradually growing, such a hillock can reach a height of 70 m with a diameter of up to 200 m. Such landforms are called hydrolaccoliths(Fig. 6).
Rice. 6. Hydrolaccolith
Work of flowing waters
Flowing waters are understood to mean all the water flowing down the land surface, ranging from small streams that occur during rains or snowmelt to the largest rivers, such as the Amazon.
Flowing waters are the most powerful of all external factors that transform the surface of the continents. Destroying rocks and carrying the products of their destruction in the form of pebbles, sand, clay and dissolved substances, flowing waters are capable of leveling the highest mountain ranges to the ground over millions of years. At the same time, the products of destruction of rocks carried by them into the seas and oceans serve as the main material from which powerful strata of new sedimentary rocks arise.
The destructive activity of flowing waters can take the form flat flush or linear blur.
Geological activity flat flush It consists in the fact that rain and melt water flowing down the slope pick up small weathering products and carry them down. Thus, the slopes are flattened, and the wash products are deposited at the bottom.
Under linear blur understand the destructive activity of water currents flowing in a certain channel. Linear erosion leads to the dismemberment of the slopes by ravines and river valleys.
In areas where there are readily soluble rocks (limestone, gypsum, rock salt), karst forms- funnels, caves, etc.
Processes caused by the action of gravity. The processes caused by the action of gravity include primarily landslides, landslides and talus.
Rice. Fig. 7. Scheme of a landslide: 1 - initial position of the slope; 2 - undisturbed part of the slope; 3 - landslide; 4 - sliding surface; 5 - rear seam; 6 - landslide ledge; 7 - landslide soles; 8- spring (source)
Rice. 8. Landslide elements: 1 — sliding surface; 2 - landslide body; 3 - stall wall; 4 - position of the slope before landslide mixing; 5 - bedrock slope
Masses of earth can slide down slopes at a barely perceptible speed. In other cases, the rate of mixing of weathering products is higher (for example, meters per day), sometimes large volumes of rocks collapse at a speed exceeding the speed of the express train.
collapses occur locally and are confined to the upper belt of mountains with a sharply dissected relief.
Landslides(Fig. 7) occur when natural processes or people disturb the stability of the slope. The cohesion forces of soils or rocks turn out to be at some point less than the force of gravity, and the entire mass begins to move. Landslide elements are shown in fig. eight.
In a number of mountain junctions, along with shedding, collapse is the leading slope process. In the lower belts of mountains, landslides are confined to slopes actively washed away by watercourses, or to young tectonic discontinuities, expressed in the relief in the form of steep and very steep (more than 35°) slopes.
Rockfalls can be catastrophic, endangering ships and coastal communities. Landslides and scree along the roads impede the operation of transport. In narrow valleys, they can disrupt flow and lead to flooding.
Scree quite common in the mountains. Shedding gravitates towards the upper belt of highlands, and in the lower belt it appears only on slopes washed away by watercourses. The predominant forms of shedding are the “peeling” of the entire slope or a significant part of it, as well as the integral process of crumbling from rocky walls.
Wind work (eolian processes)
The work of the wind is understood as a change in the surface of the Earth under the influence of moving air jets. Wind can break up rocks, carry small detrital material, collect it in certain places, or deposit it on the surface of the earth in an even layer. The greater the wind speed, the greater the work done by it.
A sand hill formed as a result of wind activity is dune.
Dunes are common wherever loose sands come to the surface, and the wind speed is sufficient to move them.
Their dimensions are determined by the volume of incoming sand, wind speed and the steepness of the slopes. The maximum speed of dune movement is about 30 m per year, and the height is up to 300 m.
The shape of the dunes is determined by the direction and constancy of the wind, as well as the features of the surrounding landscape (Fig. 9).
dunes - relief mobile formations of sand in deserts, blown by the wind and not fixed by plant roots. They occur only when the direction of the prevailing wind is sufficiently constant (Fig. 10).
The dunes can reach a height of half a meter to 100 meters. They resemble a horseshoe or sickle in shape, and in cross section they have a long and gentle windward slope and a short leeward slope.
Rice. 9. Forms of dunes depending on the direction of the wind
Rice. 10. Dunes
Depending on the wind regime, accumulations of dunes take various forms:
- dune ridges stretched along the prevailing winds or their resultant;
- dune chains transverse to mutually opposite winds;
- dune pyramids, etc.
Without being fixed, dunes under the influence of winds can change shape and mix at a speed of several centimeters to hundreds of meters per year.
To external processes, which change the relief of the earth's surface, are weathering, geological activity of flowing waters, glaciers, wind. The energy for all these processes is provided, on the one hand, by the Sun, on the other – gravitational forces.
Weathering – a set of processes of destruction of rocks. Rocks can collapse due to temperature changes, due to the fact that different minerals that make up rocks have different coefficients of thermal expansion. Over time, cracks appear in the once monolithic rock. Water can penetrate into them, which freezes at low temperatures. In this case, the expanding ice breaks the rocks, they are destroyed, and at the same time, the landforms that they form are also destroyed. Such processes are called physical weathering. They occur most intensively in areas with large annual and daily temperature amplitudes.
Other forces are working on the destruction of rocks – chemical. Water seeping into cracks gradually dissolves rocks. The dissolving power of water increases with the content of various gases in it. Limestones, gypsum, rock salt are subject to the most intensive chemical weathering. In those places where water-soluble rocks are close to the surface, numerous sinkholes, mines, funnels, and basins are observed.
Rocks can also be destroyed as a result of the vital activity of living organisms (saxifrage plants). This is biological weathering.
All water flowing from the continents to the oceans under the influence of gravity, performs a huge job of flushing and demolition of loosened rocks. Water slowly but surely destroys its bed – the rocks through which it flows. Permanent drains – rivers – form river valleys, stretching from source to mouth. The appearance of ravines is associated with temporary drains.
About a million years ago, an ice age began on Earth due to a cooling of the climate. A solid ice shell covered the northern parts of Eurasia and North America. The thickness of the glacier reached 1-2 km. The movement of such a huge mass of people could not pass without a trace for the relief of the earth's surface. The glacier, as it were, plowed and scraped the earth. The products of the destruction of rocks were frozen into the glacier, transported over great distances, and then, when the glacier melted, they were "projected" onto the earth's surface. Fjords are common within the boundaries of glaciations – long narrow bays, lake basins with intricately indented coastline, huge boulders, as well as low hills and ridges arising from glacier deposits – moraines. Glacial landforms are most common in Eurasia and North America.
Geological wind activity most clearly expressed in open spaces, which are completely or partially devoid of vegetation. Under such conditions, the wind carries a large number of sand and dust. Where the wind weakens, the sand falls to the ground and a pile is formed. Often even a small bush can become a barrier to the wind and cause the formation of sand mounds. This is how small, and then large sandy hills are formed.
The wind blows a lot of small fragments and sand from the bare mountain peaks. They hit the rocks again and again and contribute to their destruction. As a result, in open spaces one can observe bizarre whims of blowing – remnants. Landforms associated with wind activity are common on all continents except Antarctica.
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From the lessons in geography, I learned a lot of interesting things about the continuous formation of the relief and about the forces that can change the face of our planet. Surprisingly, now external processes have almost the same effect on the Earth's relief as internal ones.
External processes affecting the relief
First of all, I want to say that the relief is the profile of our planet, which combines all the surface irregularities. The science of geomorphology is engaged in its study. It is she who subdivides the processes that form the relief into internal (exogenous) and external (endogenous).
External forces seek to level the Earth's relief. Destroy all ledges, and move rock fragments to depressions.
External processes include:
Weathering occurs in two ways. It can destroy the rock, or, on the contrary, accumulate it in a certain place. Then the water becomes a fixing material. Due to these processes, rocks located directly on the surface change.
Internal processes affecting the relief
They are based on the force of pressure and the power of the enormous temperatures inside the planet. These processes include:
- movement of lithospheric plates;
- seismic activity (earthquakes and volcanic eruptions);
- magmatism (changes in the viscosity of materials under the influence of the internal heat of the Earth);
- metaphorism (changes occurring in rocks due to heat inside the planet).
As a result of these processes, such relief elements as mountain ranges, new volcanic ridges, various ledges and deep depressions arise.
Currently appearance our planet is the result joint activities not only internal, but also in many respects external processes. All these forces entail serious changes in the nature of the relief.
There are many frontiers where various forces collide. This boundary character is most pronounced at the upper boundary of the lithosphere, which is a zone of collision of dynamic processes operating inside and processes occurring in and .
Most of these recent processes acts on the surface of the lithosphere or directly above it, therefore we call them external. Changes caused by the totality of internal and external processes, as well as resulting from the interaction of individual processes, mainly determine diversity - something that is of interest to people inhabiting.
internal processes. There are three types of basic processes occurring inside: the movement of matter hard rock, the movement of heated molten matter and the transformation of rocks deep under the surface of the Earth, under the influence of high pressure and high. We know about all these processes, either because we can observe them in action (an outpouring of lava from), or because we see the results of these processes (the displacement of one large rock mass up, down, or sideways relative to another).
Rice. 3. Examples of the action of internal (endogenous) processes.
Figure 3A shows how rock mass movements are typically expressed at the surface. The scale of the process is not important: blocks of rocks can be one kilometer wide or tens of kilometers wide. It is essential that under the action of internal forces, the rocks moved upwards, at least relative, causing in one case a bend, and in the other, movement along a clearly defined fault. Thus, these internal forces caused an increase in the slopes of the surface, creating in one case an almost vertical ledge.
Figure 3B shows two common ways that molten rocks moving from bottom to top affect the earth's surface. On the left side is a mass of molten rock that slowly rose from the depths of the earth's crust, having traveled many kilometers; it deformed the overlying layers, but cooled down and hardened before reaching the earth's surface. On the right is shown how the molten mass under pressure rose through a tube-shaped channel and spilled over the surface, forming a succession of layers of lava, each of which solidified before being overlaid by the next. At the same time, the previously existing rocks were not deformed, but a new cone-shaped structure was created - a layered volcanic cone (stratovolcano). Some of these cones exceed 6 kilometers and have steep slopes. Especially a lot of them on the seabed.
Finally, Figure 3B shows what can happen to rocks that are not uplifted but submerged. In some places, the layers of rocks that formed on the surface of the Earth were moved inland as a result of the bowing of the earth's crust. At a depth of 10-20 kilometers, these rocks fall into conditions where the overlying layers (and in some cases the side) are so large that it causes the rock to flow, giving it a look completely different from the original.
All these three types of internal processes are the result of the action of the thermal energy existing inside the Earth, which activates these processes on a large scale and is so great that it counteracts the force of gravity. Consequently, as we saw in the figures, internal processes in some places raise or build on the surface of the Earth.
External processes. For most (though not all) external processes, the driving forces are moving shells, which we call and . and , even if they are not in motion (especially air containing water vapor), create an environment in which the chemical exchange between and water causes the disintegration of the rock, weakening it internal communications and contributing to its destruction. This chemical interaction occurs wherever the rock comes into contact with moist air. But more than that, water and air are constantly in motion; moving along the surface of the Earth, they involve the destroyed rocks in motion, taking their particles with them. The movement of air - the wind - raises sand dunes from the particles of rocks that it carries with it; moving water - a river - deposits sediment in its channel, and sea waves beaches are built along the coast from the products of the destruction of rocks washed off the land. Moving - - (also representing part of the hydrosphere, although in a solid state) carries rock fragments and deposits them during melting. Even underground water, slowly seeping through small pores in rocks, takes with it in dissolved form minerals rocks.
With a few local exceptions, external processes occur under the influence of gravity (But the "few local" exceptions include ubiquitous and powerful chemical processes. - Approx. ed.). They crush solid rocks and carry away the products of their destruction. Since the activity of the processes in question is controlled by gravity, they carry material from higher parts of the Earth to lower ones. Due to this transfer of rock material, the uplands are gradually destroyed and become lower and lower. Sooner or later, the destruction products are deposited in areas that were originally depressions in the form of thin layers that accumulate one on top of the other. Thus, depressions are "built on", while elevations are cut off. Between them everywhere there is a constant movement down the slopes of the products of destruction of rocks.
External processes derive their energy from solar radiation entering the earth's surface. The mechanisms by which solar heat sets air and water currents and other dynamic agents in motion are briefly mentioned in Chapter Two.
Process interaction. Thus, there are two kinds of processes: internal, driven internal warmth Earth and acting mainly in the direction opposite to the direction of gravity, and external, driven solar heat and flowing under the direct influence of gravity. These two groups of processes constantly collide at the boundary, which is the solid surface of the Earth. Imagine solid ground as smooth as a billiard ball. The force of gravity on this smooth surface would be the same everywhere. Water could not flow from one place to another. However, the surface is real existing Earth not like that. Internal processes have created uplands and lowlands on it, and, consequently, slopes. Water flows down the slopes from high to low areas and carries rock particles with it. This flow of water containing rock particles is one of the external processes.
Over time, this and other external processes could flatten the surface of the land and lower it to the level of the ocean. This alignment does occur, but not on the entire land surface at the same time. The intervention of one or another internal process disrupts its course. These processes, appearing here and there, create new heights and thereby destroy the results of the leveling activity of flowing waters. Elevations are always formed somewhere, and the speed of their rise is not necessarily constant, and a regularity is not always caught in the spatial distribution. These uplifts, maintaining the continuity of external processes, give them everything new material for processing. They create slopes, but they also make the water flow faster, they create bumps that level the flowing waters and give them new energy to do this work, they cause sediment to continuously move from elevated areas to depressions and deposit there in layers built literally from fragments of rocks that once lay somewhere on a hill. Thus, there is an interaction of external and internal processes. It never seems to stop, at least not until inner part The Earth has a sufficient supply of heat to maintain internal processes and while the Sun radiates heat to the Earth's surface, imparting energy to external processes.
This cursory glance at Earth from the side shows that the Earth - living planet and that the most active and most diverse zone is confined to the surface of the lithosphere, where there is a complex interaction and collision of various forces. In this surface zone, the life of a person also proceeds and his history unfolds, the course of which is determined by the conditions of life that exist on the surface of the Earth. And since we live among all these diverse processes, we cannot but be interested in what is happening around us. The next chapter of this book deals with the surface of the Earth. It shows that the main processes that constantly move and transform rock material do not appear by chance, but form a consistent and understandable system that operates in accordance with the laws of nature.
Over time, it changes under the influence of various forces. Places where there were once great mountains are becoming plains, and in some areas there are volcanoes. Scientists are trying to explain why this is happening. And already a lot modern science known.
Reasons for transformations
The relief of the Earth is one of the most interesting mysteries of nature and even history. Because of how the surface of our planet has changed, the life of mankind has also changed. Change occurs under the influence of internal and external forces.
Among all landforms, large and small ones stand out. The largest of them are the continents. It is believed that hundreds of centuries ago, when there was no man yet, our planet had a completely different look. Perhaps there was only one mainland, which eventually broke up into several parts. Then they split up again. And all the continents that exist now appeared.
Another major form was the oceanic depressions. It is believed that earlier there were also fewer oceans, but then there were more of them. Some scientists argue that after hundreds of years new ones will appear. Others say that the water will flood some parts of the land.
The relief of the planet has changed over the centuries. Even despite the fact that a person sometimes greatly harms nature, his activity is not capable of significantly changing the relief. This requires such powerful forces that only nature has. However, a person cannot not only radically transform the relief of the planet, but also stop the changes that nature itself produces. Despite the fact that science has made a big step forward, it is not yet possible to protect all people from earthquakes, volcanic eruptions and much more.
Basic information
The relief of the Earth and the main landforms attract the close attention of many scientists. Among the main varieties are mountains, highlands, shelves and plains.
The shelf is those parts of the earth's surface that are hidden under the water column. Very often they stretch along the coast. The shelf is that type of relief that is found only under water.
Uplands are isolated valleys and even range systems. Much of what is called mountains is actually highlands. For example, Pamir is not a mountain, as many people think. The Tien Shan is also a highland.
Mountains are the most grandiose landforms on the planet. They rise above the land by more than 600 meters. Their peaks are hidden behind the clouds. It happens that in warm countries you can see mountains, the peaks of which are covered with snow. The slopes are usually very steep, but some daredevils dare to climb them. Mountains can form chains.
The plains are stability. The inhabitants of the plains are the least likely to experience changes in relief. They almost do not know what earthquakes are, because such places are considered the most favorable for life. A real plain is the most flat earthly surface.
Internal and external forces
The influence of internal and external forces on the Earth's relief is grandiose. If you study how the surface of the planet has changed over several centuries, you can see how what seemed eternal disappears. It is being replaced by something new. External forces are not able to change the Earth's relief as much as internal ones. Both the first and the second are divided into several types.
internal forces
The internal forces that change the Earth's relief cannot be stopped. But in the modern world, scientists from different countries they try to predict when and where an earthquake will occur, where a volcanic eruption will occur.
Internal forces include earthquakes, movements, and volcanism.
As a result, all these processes lead to the emergence of new mountains and mountain ranges on land and at the bottom of the ocean. In addition, there are geysers, hot springs, chains of volcanoes, ledges, cracks, depressions, landslides, volcano cones and much more.
Outside forces
External forces are not capable of producing noticeable transformations. However, they should not be overlooked. The shaping of the Earth's relief includes the following: the work of wind and flowing waters, weathering, the melting of glaciers and, of course, the work of people. Although man, as mentioned above, is not yet able to greatly change the face of the planet.
The work of external forces leads to the creation of hills and ravines, hollows, dunes and dunes, river valleys, rubble, sand and much more. Water can destroy even a great mountain very slowly. And those stones that are now easily found on the shore may turn out to be part of a mountain that was once great.
Planet Earth is a grandiose creation in which everything is thought out to the smallest detail. It has changed over the centuries. There have been cardinal transformations of the relief, and all this - under the influence of internal and external forces. In order to better understand the processes taking place on the planet, it is imperative to know about the life that it leads, not paying attention to man.
