Landforms can be positive, that is, convex (mountain, hill, hill) and negative, that is, concave (hollow, hollow, valley, ravine).

It is difficult to attribute plains and slopes to positive or negative forms. That is why the former are called plains, which in general have a flat shape, despite some - more or less - unevenness of the surface. slopes- inclined sections of the surface of the lithosphere - positive and negative forms relief. An inflection from a horizontal surface lying above to a slope is called edge of slope, an inflection from the slope to the surface lying below, - foot, or bottom of the slope.

Landforms can be of very different sizes and be in different relationships with each other (Fig. 1).

Rice. 1. Landforms of different order
A mountainous country (A) and a plain (B) are visible; within a mountainous country - ridges (1), plateaus (2), large valleys (3); on the plain - highlands (4) and lowlands (5); in the mountains - small valleys (a), dismembering ridges and plateaus; on the plain - hills (b) and wide, shallow river valleys(in).

The scale is not observed, since it is impossible to depict a mountainous country and a small valley on the same scale; small landforms have to be exaggerated

The largest positive landforms are continental protrusions, the largest negative ones are ocean depressions. Commensurate with them in terms of their area are mountainous countries, large plains, mid-ocean ridges, island arcs and other very large landforms. These forms are megarelief(from Greek me'gas- large, long), they are also called planetary landforms.

A straight line that intersects a positive landform passes through rocks. It is natural to assume that the line connecting the two opposite sides negative form, will pass through the air or through the water, but will not go deep into the rocks; and this is correct for relatively small landforms, but with large negative landforms, the situation is somewhat more complicated. Due to the sphericity of the Earth, a straight line between two opposite sides of a large negative landform - say, an oceanic trench - can pass through the earth's crust and even deep into the mantle. The concavity of the landform itself is superimposed on the general convexity of the surface of the globe. The bottom of the ocean is thus convex. For example, the equator crosses the west coast Atlantic Ocean near the mouth of the Amazon, and the east - near the city of Libreville; the arc of the equator between them is 60°; the middle of the chord subtending this arc passes at a depth of more than 850 km from the earth's surface (Fig. 2). Therefore, the rule must be formulated differently - to speak not of a straight line, but of a horizontal line connecting the opposite sides of the relief form. The horizontal line is not a straight line, it is parallel to the spherical surface of the Earth. So, a horizontal line connecting opposite sides of a positive relief shape runs inside rocks, composing this form; a horizontal line connecting opposite sides of a negative landform runs through the air or water that fills the shape.

Rice. 2. Straight and horizontal lines connecting opposite sides of an ocean trench

Large landforms that determine the nature of a vast territory - mountain ranges, plateaus, lowlands, etc. - are macrorelief(from Greek macro's- large).

Landforms of medium size, the relative heights of which usually do not exceed several tens of meters, are river valleys, secondary spurs of ridges, hills, dunes, mud volcanoes etc. - form mesorelief(from Greek me'sos- average).

microrelief

(mikro's- small) - these are small landforms that do not exceed several meters in diameter and in height; the concept of microrelief also includes nanorelief (na'nos- dwarf) - the smallest forms that do not exceed a few centimeters in height, such as ripples on the slopes of sand dunes and barkhans, swamp tussocks, animal burrows and earth emissions near them, etc. Microrelief and nanorelief forms are details of larger forms relief, complicating their surface.

Elements and landforms

EARTH RELIEF

Earth's surface - upper bound earth's crust and lithosphere, has a complex relief in the form of various irregularities: elevations, plains and depressions. Certain combinations of forms of the earth's surface, regularly repeated over vast spaces, having a similar origin, geological structure and the same type of history of development, are called relief. The science that studies the relief, its origin and development - geomorphology .

In geomorphology, elements and forms of relief, the processes of their formation and patterns of placement are considered. Modern relief The earth is the outer expression internal structure of one or another section of the earth's crust, complicated by the latest and modern tectonic movements (endogenous processes), as well as exogenous processes. Thus, the relief is a "function" of three components: geological structures, recent and modern movements, as well as exogenous processes that have taken place and are taking place on a given area of ​​the earth's surface. It is in a state of continuous change, the speed of which is determined primarily by the speed of geological processes. Geomorphology is a science located at the intersection of geography and geology. The first is engaged in a more detailed study of the external forms of relief, and the second - the internal structure of certain forms and explains their origin.

The relief is of great importance for understanding geographical patterns, the flow of exogenous geological processes, as well as applied value for construction.

Elements and landforms

Terrain features include surfaces, lines, and points. Surfaces are divided into horizontal, inclined, concave, convex and complex and form a relief shape. The intersection of relief surfaces occurs along lines or points. Divide lines are different , water — drain , plantar ridges . The highest height of the site in a given area is called the top, the lowest point of depressions in the relief is called the bottom. The bottom of the lowering of the crests of the ridges is called the pass points.

Relief forms are composed of various combinations of elements.

Depending on the location of the relief forms in relation to the horizon plane, positive (convex in relation to the horizon plane) and negative (concave) relief forms are distinguished.

Positive landforms include:

–continents – large areas of the earth's surface, protruding above the level of the World Ocean, are based on the continental type of the earth's crust;

– highlands – a vast upland consisting of a system of mountain ranges and

peaks of the Pamirs);

- mountain range - an elongated hill with relative elevations of more than 200 m and with steep, often rocky slopes, for example, ridge. Zyuratkul;

-mountain ridge - a low mountain range with more gentle slopes and a flat top, for example, the Donetsk ridge;

-mountain - an isolated hill with a height of more than 200 m, with steep slopes and a line of maximum heights, called a ridge, for example, Golaya Sopka (Shishka);

-plateau - a highland plain, vast in area, with flat summit surfaces, well-defined slopes, for example, the Siberian plateau;

-plateau - an elevated plain, bounded by well-defined, often steep slopes;

ridge - a narrow elongated hill with a steepness of slopes of more than 20 degrees and flat tops, for example, the Chernyshov ridge (ridge) in the Polar Urals;

- ridge - an elongated hill of considerable length with gentle slopes

and flat top surfaces;

-hill - a separate dome-shaped or conical hill with gentle slopes and relative elevations of less than 200 m;

– kurgan – an artificial hill;

-hillock - an isolated dome-shaped hill with a pronounced

sole line, steepness of slopes less than 25 degrees and relatively flat top;

- alluvial cone - a low hill, located at the mouth of the channel of drains and having the form of a truncated cone with slightly convex gentle slopes.

The negative forms (concave) of the relief include:

– oceans and seas ( ocean trenches ) — large areas of the earth's surface located below the level of the World Ocean, which are based on the oceanic, and along the periphery of the oceans and seas, the continental types of the earth's crust;

-basin - a decrease in considerable depth with steep slopes;

- depression — shallow depression with gentle slopes;

-valley - an elongated depression with a slope in one direction, with

slopes of various steepness and shape (terraces - Fig. 41–43);

- beam - an elongated recess of considerable length, having three sides

gentle soddy (or covered with vegetation) slopes that arose on the site of an aged ravine;

-ravine - an elongated depression (the depth and length of the ravines are different) with relatively steep and sometimes sheer bare slopes;

- a gully - a small elongated shallow depression with steep, non-soddy slopes on three sides;

- dell or hollow - an elongated depression with gentle slopes covered with vegetation, and a depth of no more than 1 ... 2 meters.

Depending on the depth and area of ​​\u200b\u200bdistribution (i.e., the size of the territory they occupy), landforms are divided into the smallest, very small, small, medium, large, largest and greatest.

The smallest forms of relief : furrows, ripples, etc., are characterized by appropriate dimensions - a few cm in height or depth, are not plotted on maps and do not have a significant impact on construction.

Very small relief forms have a height of several decimeters to 2 m (hummocks, potholes, small gullies), are plotted on large-scale maps and taken into account when planning the territory.

Small forms of relief ( microrelief ) occupy areas up to hundreds of m2 and have a height of several meters, are plotted on a map with scales of 1:10,000, 1:5000 and larger. The microrelief should be taken into account when assessing the engineering and geological conditions of the construction site.

Medium forms relief ( mesorelief ) can be traced over thousands of kilometers at a dissection depth of up to 200 m. Such reliefs are depicted on maps at a scale of 1:50,000 and make it possible to assess the engineering and geological conditions of settlements and microdistricts. Positive macroreliefs include hills, mounds, ridges, ridges of low elevations, ledges of terraces on rivers, lakes and seas; to negative macroreliefs - shallow ravines, beams, hollows, sinkholes, etc.

Small and medium landforms often have "local names", for example, ledges of erosion terraces on Southern Urals are called pristes on the river. Ai (Fig. 44) and comb river. Yuryuzan and others.

Large landforms ( macrorelief ) occupy areas of hundreds and thousands of km2, are distinguished by the dissection of the relief at a depth of 200 ... 2000 m, are displayed on maps with a scale of 1: 100,000 and 1: 1,000,000. Taganay (Fig. 45) ridges. Negative macroreliefs include large valleys, depressions of large reservoirs, in particular lakes Turgoyak and Zyuratkul. Macro reliefs are considered when placing large territories construction.

The largest landforms ( megarelief ) occupy gigantic areas of hundreds of thousands of km2 with a difference in elevations between positive and negative forms of 500 ... 4000 m, are depicted on maps with a scale of 1:10,000,000.

These include mountains Ural mountains, Volga Upland, Caspian lowland (hollow) and their parts.

The Greatest ( planetary ) relief forms are measured in millions of km2, the difference in elevations reaches 2500 ... 6500 m. Positive macroreliefs include continents, negative ones - oceanic depressions, which have a different structure of the earth's crust under them.

Chapter 3. General information about the relief
Concepts about forms and elements of landforms

Depending on sizes distinguish various landforms: 1) planetary; 2) megaforms, 3) macroforms, 4) mesoforms, 5) microforms and 6) nanoforms.

planetary forms occupy areas of hundreds of thousands and millions of square kilometers. The entire area of ​​the globe is 510 million square kilometers, therefore, the number of planetary forms is small. Planetary landforms include: 1) continents, 2) geosynclinal belts (transitional zones), 3) ocean floor, 4) mid-ocean ridges.
Continents (continents)- the largest positive landforms of the Earth. Most of them are land, although some of the continents are under the waters of the oceans (shelf, continental slope). The most important feature continents - the addition of the earth's crust of the continental type.
Ocean bed- the main part of the bottom of the World Ocean, which, as a rule, lies at depths of more than 3 km and is characterized by the spread of the earth's crust of the oceanic type.
Modern geosynclinal belts located on the border between the continents and oceans, although not everywhere. Thus, in most of the margins of the Atlantic, Indian and Arctic oceans, the continents are in direct contact with the ocean floor. A significant part of the Alpine-Himalayan geosynclinal belt (from the Mediterranean Sea to Indochina) is located within the land.
mid-ocean ridges they are the largest mountain system that passes through all the oceans and differs significantly from the ocean floor in the structure of the earth's crust. The substantiation of the selection of these particular forms as planetary ones is given in Chap. eight.

Megaforms occupy areas of hundreds or tens of thousands of square kilometers.

These include mountain ranges and lowland countries within the continents, large depressions and uplifts within the ocean floor, faults of a planetary scale, expressed in relief, etc. An example of megaforms can be the depressions of the Gulf of Mexico and caribbean, mountain systems of the Alps and the Caucasus, West Siberian Plain and the Central Siberian Plateau.

macroforms are constituent parts megaform. The areas occupied by them are measured in hundreds or thousands (rarely tens of thousands) of square kilometers. Macroforms include individual ridges and depressions of a mountainous country: for example, the Main Caucasian Range, the Kura Lowland.

Mesoforms usually measured in several square kilometers or tens of square kilometers. An example of such forms are ravines, gullies, river valleys, large accumulative forms such as dune chains or moraine ridges.

microforms

Forms nanorelief(from the Greek. nanos - dwarf) are called very small irregularities that complicate the surface of macro-, meso- and microforms. These are, for example, meadow hummocks, marmots, small erosion grooves, signs of ripples on seabed and on the surface of eolian landforms.

The division of landforms according to their size is largely arbitrary, since in nature there are no clear boundaries between the above gradations. However, despite this conventionality, differences in the scale of landforms carry certain genetic information. So, if planetary landforms, megaforms, macroforms and some mesoforms were formed as a result of the activity of endogenous processes, then the formation of most of the mesoforms, as well as micro- and nanoforms, is mainly associated with the activity of exogenous processes.

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Landform classifications

Taking into account the properties of the relief, several classifications:

1. Morphological classification, taking into account the valuelandforms

Landforms of the Earth

1. Planetary forms are continents, mobile belts, ocean beds and mid-ocean ridges;
2. Megaforms are parts of planetary forms, i.e. plains and mountains;
3. Macroforms are parts of megaforms: mountain ranges, large valleys and depressions;
4. Mesoforms are forms medium size: beams, ravines;
5. Microforms - irregularities that complicate the surface of mesoforms: karst funnels, gullies;
6. Nanoforms are very small irregularities that complicate meso- and microforms: bumps, ripples on the slopes of dunes, etc.

2. Classification by genetic traits

There are two classes:

1. Forms formed as a result of the activity of internal, endogenous forces;
2. Forms formed due to exogenous, external forces.

The first class includes two subclasses: a) forms associated with the movement of the earth's crust; b) forms associated with volcanic activity. The second class includes: a) fluvial forms; b) eolian forms; c) glacial; d) karst, etc.

3. Morphogenetic classification:

It was first proposed at the beginning of the 20th century by Engeln. He identified three categories of relief:

1. Geotectures;
2. Morphostructures;
3. Morphosculptures.

This classification was improved by Russian geomorphologists I. P. Gerasimov and Yu. A. Meshcheryakov. It takes into account the fact that the dimensions of the relief bear the imprint of origin.

This highlights:

Geotectures – the largest landforms on Earth: planetary, and megaforms. They are created by cosmic and planetary forces.

Morphostructures – large forms of the earth's surface, which are created under the influence of endogenous and exogenous processes, but with the leading and active role tectonic movements.

Morphosculptures – these are medium and small relief forms (meso-, micro and nanoforms) created with the participation of endo- and exogenous forces, but with the leading and active role of exogenous forces.

4. Classification of relief by age

The development of the relief of any territory, as shown by the American geomorphologist W. Davis, occurs in stages. Relief age can be understood as certain stages of its development. For example, the formation of a river valley after the retreat of a glacier: at first, the river cuts into the underlying rocks, there are many irregularities in the longitudinal profile, and there is no floodplain. This is the youth stage of the river valley. Then a normal profile is formed, a river floodplain is formed. This is the maturity stage of the valley. Due to lateral erosion, the floodplain expands, the flow of the river slows down, and the channel becomes winding.

There comes a stage of old age in the development of the river valley.

W. Davis took into account a complex of morphological and dynamic features and singled out three stages: youth, maturity and old age of the relief.

Literature.

1. Smolyaninov V. M. General Geography Keywords: lithosphere, biosphere, geographic envelope. Teaching aid/ V.M. Smolyaninov, A. Ya. Nemykin. - Voronezh: Origins, 2010 - 193 p.

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Forms and elements of landforms

The relief of any part of the earth's surface is composed of alternating individual relief forms, each of which consists of relief elements (for example, a river valley consists of a floodplain, terraces of the first, second, etc. orders, bedrock banks; , slopes, peak, which are closely interconnected).

According to geometric features, the following relief elements are distinguished:

- faces, or surfaces;

- edges - the intersection of two faces;

— facet angles- the intersection of three or more faces.

In a natural setting, the surfaces that limit one or another form of relief are most easily distinguished. They have different sizes and are inclined differently with respect to the horizontal plane (sea level).

According to the magnitude of the slope they are divided into:

— sub-horizontal surfaces (with angles of inclination up to 2°);

— slopes (angles of inclination of 2° or more).

Edges and especially faceted corners retain their geometric clarity only under certain conditions. As a rule, under the influence of a number of agents (water, wind, eternal Frost) they lose their morphological severity and turn into rounded smooth surfaces. The consequence of this is often observed transitions (bends of slopes) both between faces of the same shape and adjacent landforms.

Surfaces can be:

—even

— concave or

- convex

Landforms can be:

1. - closed(moraine hill, moraine depression, thermokarst depression);

- open(ravine, beam, river valley)

2. - simple(dune, dune - small in size, have regular geometric outlines, consist of relief elements);

- complex(these are combinations of several simple forms: dune chains, complex circular dunes);

3. - positive or

- negative.

The selection of positive and negative landforms does not cause difficulties when comparing neighboring simple or relatively simple landforms. So, beams are negative forms in relation to the interbeam spaces separating them. This is true, for example, both for the Central Russian Upland and the Oka-Don Plain located to the east of it. But if we take the entire Central Russian Upland as a form of relief (with gullies, ravines, river valleys), then it will act as a positive form of relief in relation to the Oka-Don Plain.

The concept of "positive" and "negative" landforms becomes even more complicated in the transition to a comparison of landforms of a higher taxonomic rank.

4. Among the landforms formed by exogenous processes, there are accumulative(formed by the accumulation of material), and denudation(or developed) landforms formed due to the removal of material (ravine, blowout basin).

The photograph (photo 1) shows a panorama of the village of Inya, where the forms described above can be distinguished.

Photo 1. Surroundings of the village of Inya (photo by V. Almatov, M. Mendeshev)

2.2. Classification of landforms by size

1. planetary landforms

2. megaforms (megas - big, long)

3. macroforms (makros - large)

4. mesoforms (mesos - medium)

5. microforms (mikros - small)

6. nanoforms (nanos - dwarf)

1. Planetary landforms - occupy an area of ​​hundreds of thousands and millions of square kilometers. The entire area of ​​the globe is 510 million sq. km. The area of ​​Russia is 17.1 million sq. km.

The number of planetary forms is small. These include: — continents; — geosynclinal belts (transitional zones);

- the bed of the oceans; - mid-ocean ridges.

Continents are the largest positive landforms of the Earth.

Most of them are land, a significant part of the continents is involved in the structure of the bottom of the oceans. Their most important feature is the addition of a continental type by the earth's crust.

The ocean bed is the main part of the ocean floor, which, as a rule, lies at depths of more than 3 km and is characterized by the spread of the earth's crust of the oceanic type.

Modern geosynclinal belts are located on the border between the continents and oceans, although not everywhere:

- so, on most of the outskirts of the Atlantic, Indian and Arctic oceans, the continents are in direct contact with the ocean floor;

- a significant part of the Alpine-Himalayan geosynclinal belt (from the Mediterranean Sea to Indochina) is located within the land.

The mid-ocean ridges are the largest mountain system that passes through all the oceans and differs significantly from the ocean floor in the structure of the earth's crust.

2. Megaforms occupy an area of ​​the order of hundreds or tens of thousands of square kilometers. These include

- mountain belts;

- flat countries within the continents;

- large depressions and uplifts within the ocean floor;

- Faults of a planetary scale, expressed in relief (for example, the San Andreas Fault in North America, passing through the city of San Francisco).

The depressions of the Gulf of Mexico and the Caribbean Sea, the mountain systems of the Alps and the Caucasus, the West Siberian Plain and the Central Siberian Plateau, Altai can serve as an example of megaforms.

3. Macroforms - are components of megaforms. The areas occupied by them are measured in hundreds or thousands, less often tens of thousands of square kilometers.

These include, for example, individual ridges and depressions of any mountainous country (North Chuisky, South Chuisky, Katunsky ridges, Chui basin, Uimon basin).

4. Mesoforms are usually measured in several square kilometers or tens of square kilometers. An example of such forms are: ravines, gullies, stream valleys, large accumulative forms such as dune chains or moraine ridges.

5. Microforms - these are irregularities that are details of larger forms. Such, for example, are karst sinkholes, erosion potholes, coastal ramparts.

6. Forms of nanorelief called very small irregularities that complicate the surface of macro-, meso- and microforms.

Such, for example, are meadow hummocks, marmots, small erosion grooves, signs of ripples on the seabed or on the surface of eolian landforms.

The division of landforms according to their size is largely arbitrary, because in nature there are no clear boundaries between the above gradations. However, despite this conventionality, differences in the scale of landforms carry certain genetic information.

So, if planetary landforms, megaforms, macroforms and some mesoforms were formed as a result of the activity of endogenous processes, then the formation of most of the mesoforms, as well as micro- and nanoforms, is mainly associated with the activity of exogenous processes.

relief elements- the simplest parts from which its various forms are built. These include:

characteristic points:

1.1 vertex— the highest point of an element or landform. It is not shown on the map, but, as a rule, it is fixed by the visual center of the upper horizontal.

1.2 saddle- a depression in the ridge, located between two hills and two hollows. It is not shown on the map, but is fixed by the ends of two ledges and the beginning of two hollows. It is the intersection of the watershed and thalweg lines.

1.3 merger- the point of convergence of two or more thalwegs. It is shown on the map as a fork of streams, ditches, or is fixed by a pattern of main and/or auxiliary contour lines.

1.4 bottom — the lowest point of an element or landform. It is not shown on the map, but, as a rule, it is fixed by the visual center of the lower horizontal.

2)breaklines:

sole- structural line of the relief, limiting the base of the slopes of its various forms. It can be horizontal (shown as a horizontal line) or inclined (its position is fixed by an imaginary line connecting the places of a sharp bend of the contour lines).

edge- the structural line of the relief, limiting upper part slope.

A sharp inflection of the slope passes along it. Like the sole, it can be horizontal and inclined.

thalweg - a structural line connecting the lowest points lying at the bottom of negative elements and landforms. As a rule, it coincides with streams, dry ditches. In other cases, it is fixed by an imaginary line connecting the places of a sharp bend of contour lines during their transition from one slope to another.

watershed- a breakline that connects the most high points, two opposite slopes of positive elements and landforms. It is fixed by an imaginary line connecting the places of a sharp bend of the contour lines during their transition from one slope to another. Watershed is center line such relief elements as a ridge, a rib, a lintel.

The combination of the above points and lines is relief frame.

3) the simplest spatial elements:

mound - an isolated conical or dome-shaped hill with a pronounced plantar line. Hillock - above 10 meters, tubercle - below 10 meters, microtubercle - off-scale in size in plan.

ridge- a narrow, elongated hill with steep slopes, a flat or rounded top and a pronounced plantar line.

ledge- an elevation on a slope, the transverse profile of which has a slight inclination towards the general slope of the surface. Feature protrusion in that its width along the slope is approximately equal to or less than the protrusion from the slope. It is stretched across the slope.

edge- an elongated, narrow elevation with an inclined top surface on the slope.

terrace - a horizontal or inclined platform, elongated along the slope. In the transverse profile, its surface is horizontal or slightly inclined. The size of the terrace along the slope significantly exceeds its size across.

pit- a round or oval cavity with a pronounced edge.

stage- a recess in a slope, the dimensions of which along the slope are less than or equal to the transverse ones.

pass- an oblong sharp depression between the slopes of two adjacent positive elements or landforms, open on both sides. Its bottom is horizontal or slightly inclined.

saddle- as a spatial element of the relief, it is characterized by a depression in the ridge, located between two hills and two hollows.

jumper- an oblong, narrow elevation, completing two adjacent slopes and bounded at the ends by ledges or ribs descending to it. May be horizontal or slightly inclined.

dell - an elongated recess, open towards the general slope of the surface, having sod slopes on three sides.

scour- an elongated recess of insignificant length, open towards the general inclination of the surface, having steep, non-soddy slopes on three sides. Hollows and gullies, the mouth of which is located above the foot of the slope, are called hanging.

monotonous slope- a soddy inclined surface that does not have other relief elements within its area.

cliff- a steep, unturfed earthen slope. The height of the cliff is determined not by the length of the strokes in its sign, but by the number of contour lines approaching the cliff and closing on it.

Any, even the most complex, relief can be depicted on a map by a combination of its simplest elements.

The study of the origin of the relief, the history of its development, internal structure and dynamics is engaged in geomorphology(from Greek ge - Earth, morphe - form, logos - teaching).

The relief consists of landforms- natural bodies, which are parts of the relief and have a certain size. Among the landforms, positive and negative are distinguished (the morphographic principle of classification). positive forms rise above the horizontal line, representing the elevation of the surface. Their examples are hillock, hill, mountain, plateau, etc. Negative forms relief in relation to the horizontal plane form depressions. These are valleys, ravines, beams, depressions.

Landforms are made up of landforms. relief elements- separate parts of landforms: surfaces (faces), lines (edges), points, angles in the aggregate forming landforms. Among the external signs of landforms is the degree of their complexity. On this basis, one distinguishes simple and complex forms. simple shapes(hill, hollow, hollow, etc.) consist of separate morphological elements, the combination of which forms the form. For example, at a hillock, a sole, slopes and top are distinguished. Complex forms are made up of a number of simple ones. An example is a valley, which includes slopes, a floodplain, a channel, etc.

According to the slope, the surfaces are divided into sub-horizontal ones with a slope of less than 2 0 and inclined surfaces (slopes) with large slopes. Slopes can have a different shape and be straight, concave, convex, stepped. Surfaces can be smooth, convex and concave. Along strike - closed and open. According to the degree of dissection of the surface, flat and mountainous territories are distinguished.

The combination of relief forms that have a similar origin and regularly repeat in a certain space forms relief type. On larger expanses of the earth's surface, it is possible to combine individual types of relief on the basis of their similar origin or difference. In this case, one speaks of relief type groups. Since the association of relief types is carried out on the basis of their origin, they speak of genetic types relief.

The two most common types of land relief are mountainous and flat. According to the height, the plains are divided into depressions, lowlands, uplands, plateaus and plateaus, and the mountains are divided into low, medium, high and highest.

By size, landforms are divided into planetary forms, with an area of ​​millions of km 2 with a range of heights of 2.5-6 thousand m - these are the continents, geosynclinal belts, the ocean floor, SOHs. Megaforms- an area of ​​​​hundreds and thousands of km 2 with a range of heights of 500-4000 m - these are parts of planetary forms - plains and mountainous countries. macroforms- an area of ​​​​hundreds of km 2 with a range of heights of 200-2000 m. - these are large ridges, large valleys and depressions. Mesoforms- with an area of ​​​​up to 100 km 2 with a height span of 200-1000 m - these are, for example, large beam systems. microforms with an area of ​​up to 100 m 2 and a height span of up to 10 m - these are gullies, karst funnels, suffusion saucers, dunes, etc.). Nanoforms with an area of ​​​​up to 1 m 2 and a height span of up to 2 m - these are marmots, the smallest depressions, bumps, etc.).

According to the morphogenetic classification, all landforms are divided into geotectures- irregularities formed under the influence of endogenous forces - ledges of the continents and depressions of the oceans, morphostructures- irregularities formed under the influence of endogenous and exogenous forces, and the leading ones are endogenous - these are plains and mountainous countries, morphosculptures- landforms formed by exogenous forces - small irregularities complicating the surfaces of mountains and plains.

Plains- these are areas of the land surface, the bottom of the seas and oceans, which are characterized by: slight fluctuations in altitude (up to 200 m) and a slight slope of the terrain (up to 5 °). Depending on the absolute heights, there are: low-lying (up to 200 m); elevated (200-500 m); upland or high (more than 500 m) plains.

A mountain is a positive landform, rising above a relatively flat area by at least 200 m. The mountain is bounded by slopes on all sides. The transition from slopes to plains is the bottom of the mountain. The most high part mountains are her vertex.

With very gentle slopes, a positive landform with a height of more than 200 m is called - hill.

The mountains – these are highly dissected areas of the earth's surface, raised high above the level of the Ocean. At the same time, the mountains have a single base, rising above the adjacent plains, and consists of many positive and negative landforms. In terms of height, low mountains up to 800 m are distinguished, middle mountains - 800-2000 and high mountains - more than 2000 m.

The age of the relief can be: absolute - determined by geochronological scale; relative - the formation of a relief is established earlier or later than any other form or surface.

The relief is formed as a result of the constant interaction of endogenous and exogenous forces. Endogenous processes mainly create the main features of the relief, while exogenous processes try to level it. The sources of energy in relief formation are: the internal energy of the Earth, the energy of the Sun and the influence of space. Relief formation occurs under the influence of gravity. The energy source of endogenous processes is thermal energy Earth associated with radioactive decay in the mantle. Due to endogenous forces, the earth's crust was separated from the mantle with the formation of its two types: continental and oceanic. Endogenous forces cause movements of the lithosphere, the formation of folds, faults, earthquakes and volcanism.

Movements of the lithosphere are characterized by different directions and intensity in time and space. In the direction relative to the Earth's surface, vertical and horizontal movements; by direction - reversible (oscillatory) and irreversible; according to the speed of manifestation - fast (earthquakes) and slow (secular).

Horizontal movements of the lithosphere are manifested in the slow movement of huge lithospheric plates along with continents and oceans along the plastic asthenosphere. Deep faults (rifts) separating the plates are usually located at the bottom of the oceans, where the earth's crust is the thinnest (5-7 km). Magma rises along the faults and, solidifying, builds up the edges of the plates, forming the Mid-Ocean ridges. As a result, the plates move apart, moving away from each other at a rate of 1-12 cm/year. Their separation leads to a collision with neighboring plates, or to immersion (diving) under them. At the same time, the edges of neighboring plates rise, which leads to the emergence of mountain-building processes and mobile belts, which are characterized by high volcanism and seismicity. Example: Far East. Changes in the planetary relief of the Earth are associated with a decrease in the speed of its rotation as a result of the decelerating effect of the Moon. The stresses that arise in the body of the Earth in this case cause deformation of the earth's crust and movement of the plates of the lithosphere.

Vertical movements lithospheric plates are caused by the fact that mountains, composed of lighter rocks, have a more powerful earth's crust, and under the ocean it is thin and covered with water. The mantle here comes close to the surface, which compensates for the lack of mass. Additional loading, for example, the formation of an ice cover, leads to the "pressing" of the earth's crust into the mantle. So Antarctica sank 700 m, and in its central parts the land was below the Ocean. The same thing happened in Greenland. Release from the glacier leads to the uplift of the earth's crust: Scandinavian Peninsula is now rising at a rate of 1 cm/year. The vertical movements of smaller blocks are always reflected in the relief. Particularly visible are the forms created by modern (neotectonic) movements. For example, in the Central Chernozem region, the area of ​​the Central Russian Upland rises by 4-6 mm/year, while the area of ​​the Oka-Don Lowland falls by 2 mm/year.

Vertical and horizontal movements of the earth's crust lead to deformation of rock layers, leading to two types of dislocations: folded - bending of the layers without violating their integrity, and discontinuous, where, as a rule, the crust blocks move in vertical and horizontal directions. Both types of dislocations are characteristic of the mobile belts of the Earth, where mountains are formed. However, folded dislocations are practically absent in the platform cover. Dislocations in mountains are accompanied by magmatism and earthquakes.

Exogenous processes are associated with the arrival on Earth solar energy, but they flow with the participation of gravity. In this case, the weathering of rocks and the movement of material under the action of gravity occur: landslides, landslides, screes, material transfer by water and wind. Weathering is a set of processes of mechanical destruction and chemical change breeds. The general effect of the processes of destruction and transport of rocks is called denudation, which leads to the leveling of the surface of the lithosphere. If there were no endogenous processes on Earth, then our planet would have had a completely flat surface long ago. This imaginary surface is called the main level of denudation. In reality, there are many temporal levels of denudation at which equalization processes may fade for some time. The intensity of manifestation of denudation processes depends on the composition of rocks and climate. Highest value at the same time, it has the height of the terrain above sea level, or the basis of erosion.

Exogenous processes, smoothing out large irregularities of the earth's surface, form a smaller relief - denudation and accumulative morphosculpture. The variety of exogenous processes, as well as denudation and accumulative landforms resulting from their manifestation, can be combined into the following types:

1. activity surface water(temporary streams and rivers) - fluvial relief;
2. groundwater - karst, suffusion and landslide relief;
3. glaciers and melted glacial waters - glacial (glacial) and water-glacial relief;
4. changes under the influence of various processes in permafrost rocks - permafrost (cryogenic) relief;
5. wind activity - eolian relief;
6. coastal marine processes - the relief of sea coasts;
7. living organisms - biogenic relief;
8. man - anthropogenic relief.

As can be seen, the relief of the surface of the lithosphere is the result of the counteraction of endogenous and exogenous processes. The former create uneven terrain, while the latter smooth them out. Relief formation can be dominated by endo- or exogenous forces. In the first case, the height of the relief increases - this is an upward development of the relief. In the second, positive landforms are destroyed and depressions are filled. This is a downward development.

Negative landforms

positive landforms

The history of the formation of the relief of the region.

The modern relief is the result of the development of the ancient Russian platform over a long period. In its formation, 3 periods are distinguished:

1. Pre-glacial (long) - is the result of tectonic movements.

2. Glacial - accumulation of deposits of melted glacial waters.

3. Postglacial - as a result of the destroyed and accumulative activity of surface waters.

The plain appearance of the Russian platform and, together with it, the territory of the region acquired 500 million years ago as a result of the denudation (destruction) of the ancient mountains of Karelid.

AT further destruction occurs under the influence of tectonic movements. By the beginning of the definition on the territory of the region. a highly dissected relief was formed.

Large landforms were formed mainly before the glaciers in the Mesozoic and Cenozoic.

As a result of erosive-accumulative activity appearance region changes radically.

Territory was covered with a thick layer of new rocks. The terrain was leveled. Many pre-glacial plains were not only buried, but accumulative ridges formed on them. The accumulation caused a significant restructuring of the river network. Large hollows formed after the melting of ice, flowing lakes formed.

Geologists found that the territory of the region. in the Quaternary period it was subjected to glaciations at least 3 times.

1. The most ancient Dnieper glacier, completely covered the territory of the region.

2. The Moscow glacier has spread over almost the entire territory of the region, except for the southern regions.

3. The Valdai glacier captured only the northwestern region.

The main stratum of the Quaternary deposits belongs to the Dnieper glaciation. Widespread in the region. landforms associated with the activity of melted glacial waters. Water flows created hollows, outwash plains, etc.

In the last period, there is a tendency for a general rise in the territory of the region. The highest rate of uplift is characteristic of the Smolensk and Vyazemskaya Uplands, up to 3 mm per year. This is due to the activity of glaciers and melted glacial waters.

The bumps and manes have relative height from 1 to 10 m

The hills have a relative height of 10 to 100 m

The ridges are comparable in relative height with the hills. In contrast, they have an elongated shape.

There are closed, open on one side (semi-closed) and open on both sides (unclosed) negative landforms.

closed:

- saucers shallow, poorly expressed closed depressions in the relief various shapes depth no more 1 m.

- depressions They are depressions of various forms, with a depth of 1 to 10 m, gentle slopes, a well-defined lowest mark, or usually a small area of ​​a flat bottom.

- hollows comparable in depth to depressions, but unlike them, they have steep or relatively steep slopes and a flat bottom.

- lowlands have varied, sometimes complex configuration, gentle slopes, uneven bottom. They occupy relatively large areas. Their depth varies from 10 to 100 m.

- hollows are characterized by the same depth as the lowlands, but have steep or relatively steep slopes similar to the depressions and a bottom that is flat or with separate irregularities.

Semi-closed:

- hollow

- dell

- beam. Related to human activities: ravines, gullies, gaps.

Open:

- Valley It is a linearly elongated relief depression with a uniform general bottom slope and clearly visible slopes. Valleys vary in size, depth, complexity of structure. The features of the device and the size of the valleys depend mainly on the genesis and time of their formation, the power of the watercourse, and the nature of the constituent rocks.

Big influence on relief have anthropogenic factors(deforestation, etc.).

Negative landforms - concept and types. Classification and features of the category "Negative landforms" 2017, 2018.

Landform classifications

There are several classifications of landforms of the Earth, which have different grounds. According to one of them, two groups of landforms are distinguished:

• positive - convex in relation to the plane of the horizon (continents, mountains, hills, hills, etc.);
• negative - concave (oceans, basins, river valleys, ravines, beams, etc.).

The classification of the forms of the Earth's relief by size is presented in Table. 1 and in fig. one.

Table 1. Landforms of the Earth by size

Rice. 1. Classification largest forms relief

We will separately consider the relief forms characteristic of the land and the bottom of the World Ocean.

The relief of the Earth on the map of the World

Ocean floor landforms

The bottom of the World Ocean is divided by depth into the following components: continental shelf (shelf), continental (coastal) slope, bed, deep-sea (abyssal) basins (troughs) (Fig. 2).

continental shelf — coastal part seas and lying between the coast and the continental slope. This former coastal plain in the topography of the ocean floor is expressed as a shallow, slightly rolling plain. Its formation is mainly associated with the subsidence of individual land areas. This is confirmed by the presence within the continental shelf of underwater valleys, coastal terraces, fossil ice, permafrost, remnants of terrestrial organisms etc. Continental shallows are usually distinguished by a slight bottom slope, which is practically horizontal. On average, they drop from 0 to 200 m, but depths of more than 500 m can occur within their limits. The relief of the continental shoal is closely related to the relief of the adjacent land. On mountainous coasts, as a rule, the continental shelf is narrow, and on flat coasts it is wide. The continental shelf reaches its greatest width off the coast of North America - 1400 km, in the Barents and South China Seas - 1200-1300 km. Typically, the shelf is covered with clastic rocks brought by rivers from land or formed during the destruction of the coast.

Rice. 2. Landforms of the ocean floor

Continental slope - the inclined surface of the bottom of the seas and oceans, connecting the outer edge of the continental shoal with the ocean floor, extending to a depth of 2-3 thousand m. It has rather large angles of inclination (on average 4-7 °). The average width of the continental slope is 65 km. Off the coast of coral and volcanic islands, these angles reach 20-40°, and near the coral islands there are angles and larger, almost vertical slopes - cliffs. Steep continental slopes lead to the fact that in the areas of maximum inclination of the bottom, masses of loose sediments slide down to the depths under the action of gravity. In these areas, a bare sloping bottom can be found.

The relief of the continental slope is complex. Often the bottom of the continental slope is indented by narrow deep canyon gorges. They often visit steep rocky shores. But there are no canyons on continental slopes with a gentle slope of the bottom, and also where outside the continental shelf there are peninsulas of islands or underwater reefs. The tops of many canyons adjoin the mouths of existing or ancient rivers. Therefore, canyons are considered as an underwater continuation of flooded riverbeds.

Another characteristic element of the relief of the continental slope are underwater terraces. These are the underwater terraces of the Sea of ​​Japan, located at a depth of 700 to 1200 m.

Ocean bed- the main expanse of the bottom of the World Ocean with prevailing depths of more than 3000 m, extending from the underwater margin of the mainland into the depths of the ocean. The area of ​​the ocean floor is about 255 million km 2, i.e., more than 50% of the bottom of the World Ocean. The bed is distinguished by insignificant angles of inclination, on average they are 20-40 °.

The relief of the ocean floor is no less complex than that of the land. The most important elements of its relief are abyssal plains, oceanic basins, deep-sea ridges, mid-ocean ridges, uplands and underwater plateaus.

In the central parts of the oceans are located mid-ocean ridges, rising to a height of 1-2 km and forming a continuous ring of uplifts in southern hemisphere at 40-60°S sh. Three ridges extend northward from it, extending meridianally, in each ocean: the Mid-Atlantic, Mid-Indian and East Pacific. The total length of the Middle Oceanic Ranges is more than 60,000 km.

Between the mid-ocean ridges are deep-sea (abyssal) plains.

abyssal plains — flat surfaces bottom of the World Ocean, which lie at depths of 2.5-5.5 km. It is the abyssal plains that occupy approximately 40% of the ocean floor area. Some of them are flat, others are wavy with a height amplitude of up to 1000 m. One plain is separated from the other by ridges.

Some of the solitary mountains located on the abyssal plains protrude above the surface of the water in the form of islands. Most of these mountains are extinct or active volcanoes.

Strings of volcanic islands above a subduction zone, where one oceanic plate subducts under another, are called island arcs.

In shallow waters in tropical seas (mainly in the Pacific and Indian Oceans), coral reefs are formed - calcareous geological structures formed by colonial coral polyps and some types of algae that can extract lime from sea water.

About 2% ocean floor occupy deep-water (over 6000m) depressions - gutters. They are located where the oceanic crust subducts under the continents. These are the deepest parts of the oceans. Over 22 known deep sea trenches, of which 17 are in the Pacific Ocean.

landforms

The main landforms on land are mountains and plains.

The mountains - isolated peaks, massifs, ridges (usually more than 500 m above sea level) of various origins.

In general, 24% of the earth's surface is covered by mountains.

The highest point of the mountain is called mountain peak. The highest mountain peak of the Earth is Mount Chomolungma - 8848 m.

Depending on the height, the mountains are low, medium, high and highest (Fig. 3).

Rice. 3. Classification of mountains by height

The highest mountains of our planet - the Himalayas, an example high mountains can serve as the Cordillera, Andes, Caucasus, Pamir, medium - the Scandinavian mountains and the Carpathians, low - the Ural Mountains.

In addition to the aforementioned mountains, the globe there are many others. You can get acquainted with them on the maps of the atlas.

According to the method of formation, they are distinguished the following types mountains:

• folded - formed as a result of crushing into folds of a thick layer of sedimentary rocks (mainly formed in the Alpine era of mountain building, therefore they are called young mountains) (Fig. 4);
• blocky - formed as a result of raising on great height hard blocks of the earth's crust; characteristic of ancient platforms: the internal forces of the Earth split the rigid foundation of the platforms into separate blocks and raise them to a considerable height; as a rule, ancient or revived) (Fig. 5);
• folded-blocky - these are old folded mountains that have largely collapsed, and then, in new periods of mountain building, their individual blocks were again raised to a great height (Fig. 6).

Rice. 4. Formation of folded mountains

Rice. 5. Formation of old (blocky) mountains

According to the location, epigeosynclinal and epiplatform mountains are distinguished.

By origin, mountains are divided into tectonic, erosional, volcanic.

Rice. 6. Formation of fold-block renewed mountains

tectonic mountains- these are mountains that were formed as a result of complex tectonic disturbances of the earth's crust (folds, thrusts and various kinds of faults).

Erosive mountains - highly elevated plateau-like areas of the earth's surface with a horizontal geological structure, strongly and deeply dissected by erosion valleys.

Volcanic mountains - these are volcanic cones, lava flows and tuff covers, distributed over a large area and usually superimposed on a tectonic base (on a young mountainous country or on ancient platform structures, such as volcanoes in Africa). Volcanic cones formed by accumulations of lava and rock fragments erupted through long cylindrical vents. These are the Maoin mountains in the Philippines, Mount Fuji in Japan, Popocatepetl in Mexico, Misty in Peru, Shasta in California, etc. Thermal cones have a structure similar to volcanic cones, but are not so high and are composed mainly of volcanic slag - a porous volcanic rock that looks like ash.

Depending on the areas occupied by mountains, their structure and age, mountain belts, mountain systems, mountainous countries, mountain prices, mountain ranges and uplifts of a smaller rank are distinguished.

mountain range called a linearly elongated positive landform, formed by large folds and having a significant length, for the most part in the form of a single watershed line, along which the most
significant heights, with clearly defined ridges and slopes facing in opposite directions.

Mountain chain- a long mountain range, elongated in the direction of the general strike of the folds and separated from adjacent parallel chains by longitudinal valleys.

mountain system- formed during one geotectonic epoch and having spatial unity and a similar structure, a set of mountain ranges, chains, highlands(extensive mountain uplifts, which are a combination of high plains, mountain ranges and massifs, sometimes alternating with wide intermountain basins) and intermountain depressions.

Mountain country- a set of mountain systems formed in one geotectonic epoch, but having various structure and appearance.

mountain belt- most large unit in the classification of mountain relief, corresponding to the largest mountain structures, combined spatially and according to the history of development. Usually the mountain belt stretches for many thousands of kilometers. An example is the Alpine-Himalayan mountain belt.

Plain- one of the most important elements of the relief of the land surface, the bottom of the seas and oceans, characterized by small fluctuations in heights and slight slopes.

The scheme of formation of plains is shown in fig. 7.

Rice. 7. Formation of plains

Depending on the height, among the land plains, there are:

• lowlands - having absolute altitude from 0 to 200 m;
• elevations - not higher than 500 m;
• plateaus.

Plateau- a vast area of ​​relief with a height of 500 to 1000 m or more, with a predominance of flat or slightly undulating watershed surfaces, sometimes separated by narrow, deeply incised valleys.

The surface of the plains can be horizontal and inclined. Depending on the nature of the mesorelief that complicates the surface of the plain, flat, stepped, terraced, undulating, ridged, hilly, hilly, and other plains are distinguished.

According to the principle of the predominance of existing exogenous processes, the plains are divided into denudation, formed as a result of the destruction and demolition of previously existing uneven terrain, and accumulative resulting from the accumulation of loose sediments.

Denudation plains, the surface of which is close to the structural surfaces of a slightly disturbed cover, are called reservoir.

Accumulative plains are usually subdivided into volcanic, marine, alluvial, lacustrine, glacial, etc. Accumulative plains of complex origin are also common: lacustrine-alluvial, delta-marine, alluvial-proluvial.

The general features of the relief of the planet Earth are the following:

Land occupies only 29% of the Earth's surface, which is 149 million km2. The bulk of the land mass is concentrated in the Northern Hemisphere.

The average land height of the Earth is 970 m.

On land, plains and low mountains up to 1000 m high prevail. Mountain elevations above 4000 m occupy an insignificant area.

The average depth of the ocean is 3704 m. The relief of the bottom of the World Ocean is dominated by plains. The share of deep-sea depressions and trenches accounts for only about 1.5% of the ocean area.

There are positive (rising above the surface) and negative (deepering from the surface) landforms.

Irregularities in the surface of the earth's crust can be of a different order.

The Greatest (planetary) forms relief - these are oceanic depressions (negative form) and continents (positive form)

The area of ​​the earth's surface is 510 million sq. km. of which 361 mln. km (71%) occupies and only 149 million square meters. km (29%) - land

Land is unevenly distributed among the oceans. In the Northern Hemisphere, it occupies 39% of the area, and in the Southern - only 19%.

The mainland or part of the mainland with nearby islands is called part of the world.

Parts of the world: Europe, Asia, America, . As a special part of the world, Oceania is distinguished - a collection of islands in the central and southwestern parts.

Continents and islands divide the single World Ocean into parts - oceans. The boundaries of the oceans coincide with the shores of the continents and islands.

Oceans protrude into the land by seas and bays.

Sea - a part of the ocean, more or less isolated from it by land or elevations of underwater relief. There are marginal, inland, inter-island seas.

gulf - part of the ocean, sea, lake, deeply protruding into the land.

strait - a relatively narrow body of water, bounded on both sides by land. The most famous straits are: Bering, Magellan, Gibraltar. The Drake Passage is the widest, 1000 km, and the deepest, 5248 m; the longest is the Mozambique Channel, 1760 km.

Planetary relief elements are divided into second-order relief forms - megaforms (mountain structures and large plains). Within megaforms allocate macroforms (mountain ranges, mountain valleys, depressions of large lakes). On the surface of macroforms, there are mesoforms (forms of medium size - hills, ravines, beams) and microforms (small forms with height fluctuations of several meters - dunes, gullies).

Mountains and plains

- vast areas of land or the ocean floor, significantly elevated and strongly dissected. The mountain is a single uplift with a peak, having a relative height of more than 200 m. Most of these mountains are of volcanic origin. Unlike a mountain, a hill has a lower relative height and gentler slopes, gradually turning into a plain.

Mountain ranges are linearly elongated uplifts with clearly defined slopes and ridges. The ridge part of the ridge is usually very uneven, with peaks and passes. The ridges connect and intersect, forming mountain ranges and mountain nodes - the highest and difficult sections mountains Combinations of mountain ranges, often heavily destroyed, intermountain basins and leveled elevated areas form highlands. According to the absolute height, mountains are distinguished high (above 2000 m), medium high (800 - 2000 m) and low (not higher than 800 m).

The general pattern of relief changes with height is its. The higher, the more intense the weathering in the mountains. The tops of the mountains, rising above the snow line, bear on themselves. Below, glacial tongues descend, feeding turbulent mountain streams, streams dissect the slopes with deep valleys, and move pumps down. At the foot, the pumps and the material crumbling from the slopes stick together, smoothing out the bends of the slopes, creating foothill plains.

– surface areas with small height differences. Plains with an absolute height of no more than 200 m are called lowlands; no more than 500 m - elevated; above 500 m - upland or plateaus. On the continents, most of the plains were formed on platforms and folded layers of the sedimentary cover (stratified plains). Plains that have arisen as a result of the demolition of destruction products from the remaining base of the mountains (basement) are called basement. Where material accumulates, leveling the surface, accumulative plains form. Depending on the origin, the plains are sea, lake, river, glacial, volcanic.

Deep-water plains are hilly, undulating, less often flat. Significant thicknesses of sediments accumulate at the foot of the continental slope, forming sloping plains. flat relief also has a shelf. Usually it represents the outskirts of the platform, which turned out to be under sea level. On the shelf, there are landforms that have arisen on land, riverbeds, and forms of glacial relief.

Formation of the Earth's relief

Features of the Earth's relief