Positive landforms. Great encyclopedia of oil and gas

Types of relief Various reliefs occupy a significant place in woodworking. Performing them requires a certain skill. The more complex the terrain, the more skill is required. Relief is a semi-volume image placed on a plane and protruding to varying degrees

Highland type of relief

Alpine type of relief

Relief section

Relief maps

Relief edges

Positive landforms

Relief inversion

Chapter 35. P.S.A. for relief About forty years ago in a small town on the west coast there stood a large, shapeless structure surrounded by a high plank fence. It resembled a concentration camp, but in fact it was a factory and warehouse where they produced and profitably

Study of the relief

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Study of relief One of the most important objects of observation is relief, i.e. the totality of unevenness of the earth's surface - lowlands, plateaus, mountain ranges, river valleys, ravines, gullies, etc. Having studied the terrain, you can get an idea of ​​its Landforms can be positive , that is, convex (mountain, hill, hill) and negative

, that is, concave (depression, basin, valley, ravine). It is difficult to classify plains and slopes as positive or negative forms. That's why the first ones are called plains Slopes- inclined sections of the lithosphere surface - positive and negative relief forms are separated and limited. The bend from the overlying horizontal surface to the slope is called edge of the slope, 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 orders
A mountainous country (A) and a plain (B) are visible; within a mountainous country - ridges (1), plateaus (2), large valleys (3); on the plain - highland (4) and lowland (5); in the mountains - small valleys (a) dividing ridges and plateaus; on the plain there are hills (b) and wide, shallow river valleys (c).

The scale is not respected, 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 trenches. Comparable in area are mountainous countries, large plains, mid-ocean ridges, island arcs and other very large landforms. These forms make up megarelief(from Greek me'gas- large, long), they are also called planetary landforms.

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

Rice. 2. Straight and horizontal lines connecting opposite sides of the oceanic trench

Large landforms that determine the natural features of a vast territory - mountain ranges, plateaus, lowlands, etc. - are macrorelief(from Greek makro's- big).

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

Microrelief

(mikro's- small) are small relief forms, not exceeding several meters in diameter and height; The concept of microrelief also includes nanorelief (na'nos- dwarf) - the smallest forms, not exceeding a few centimeters in height, such as, for example, ripples on the slopes of sand dunes and dunes, swamp hummocks, animal holes and earth emissions near them, etc. Forms of microrelief and nanorelief are details of larger forms relief, complicating their surface.

Elements and forms of relief

RELIEF OF THE EARTH

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

Geomorphology examines the elements and forms of relief, the processes of their formation and patterns of placement. The modern relief of the Earth is an external expression of the internal structure of a particular section of the earth’s crust, complicated by the latest and modern tectonic movements (endogenous processes), as well as exogenous processes. Thus, relief is a “function” of three components: geological structures, recent and contemporary movements, as well as exogenous processes that have occurred and are occurring 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 at the intersection of geography and geology. The first deals with a more thorough study of external forms of relief, and the second deals with the internal structure of certain forms and explains their origin.

Relief is of great importance for understanding geographical patterns, the course of exogenous geological processes, as well as practical significance for construction.

Elements and forms of relief

Relief elements 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. Dividing lines differ , water — drain , plantar and eyebrows . The highest elevation of a site in a given area is called the top, the lowest point of relief depression is called the bottom. The bottom of the depression of the ridge crests is called pass points.

Landforms are made up 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, based on the continental type of the earth's crust;

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

Pamir peaks);

– 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 gentler slopes and a flat top, for example the Donetsk Ridge;

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

– plateau – a mountainous plain, vast in area, with flat top surfaces and 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 slopes steeper 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 – an isolated dome-shaped or conical hill with gentle slopes and relative elevations of less than 200 m;

–mound – artificial hill;

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

a plantar line, slopes less than 25 degrees steep and a relatively flat top;

– alluvial cone is a low hill located at the mouth of the drainage channel and having the appearance of a truncated cone with slightly convex gentle slopes.

Negative forms of relief (concave) include:

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

– basin – a depression of 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 depression of considerable length, having three sides

gentle turfed (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 steep exposed slopes;

– a ravine is a small elongated shallow depression with steep, unturfed slopes on three sides;

– dell or drainage basin – 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 ​​distribution (i.e. the size of the territory they occupy), landforms are divided into the smallest, very small, small, medium, large, largest and greatest.

Smallest landforms : 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 from several decimeters to 2 m (hummocks, potholes, small gullies), are plotted on large-scale maps and taken into account when planning the territory.

small relief forms ( microrelief ) occupy areas of 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. Microrelief must be taken into account when assessing the engineering and geological conditions of a construction site.

Medium shapesrelief ( mesorelief ) can be traced over thousands of kilometers at a 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, terrace ledges on rivers, lakes and seas; to negative macroreliefs - shallow ravines, beams, hollows, karst sinkholes, etc.

Small and medium-sized landforms often have “local names”, for example, the ledges of erosional terraces in the Southern Urals are called ledges on the river. Ai (Fig. 44) and Grebnyamina river. Yuryuzan et al.

Large relief forms ( 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. Positive macroreliefs include mountain ranges, mountains and mountain ranges, for example, Zyuratkul and Taganaysky (Fig. 45) ridges. Negative macroreliefs include large valleys, depressions of large reservoirs, in particular lakes Turgoyak and Zyuratkul. Macro reliefs are taken into account when locating large construction areas.

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

These include mountains, for example the Ural Mountains, the Volga Upland, the Caspian Lowland (basin) and their parts.

Greatest ( planetary ) relief forms are measured in millions of km2, the difference in elevations reaches 2500...6500 m. Positive macroreliefs include continents, negative macroreliefs include oceanic depressions, which have different structures of the earth’s crust underneath them.

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

Depending on the size highlight 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 (transition zones), 3) ocean floor, 4) mid-ocean ridges.
Continents- the largest positive landforms on Earth. Most of them are land, although some of the continents are located under the waters of the World Ocean (shelf, continental slope). The most important feature of the continents is the composition of the earth's crust of the continental type.
ocean bed- the main part of the bottom of the World Ocean, lying, as a rule, at depths of more than 3 km and characterized by the distribution of the earth’s crust of the oceanic type.
Modern geosynclinal belts located on the border between continents and oceans, although not everywhere. Thus, on 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 on land.
Mid-ocean ridges They are the largest mountain system passing through all the oceans and differ significantly from the ocean bed in the structure of the earth's crust. The rationale for identifying these particular forms as planetary is given in Chapter. 8.

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

These include mountain belts and lowland countries within continents, large depressions and uplifts within the ocean floor, faults on a planetary scale, expressed in relief, etc. Examples of megaforms include the depressions of the Gulf of Mexico and the Caribbean Sea, the mountain systems of the Alps and Caucasus, Western -Siberian Plain and Central Siberian Plateau.

Macroforms are components of megaforms. The areas occupied by them are measured in hundreds or thousands (less often tens of thousands) of square kilometers. Macroforms include individual ridges and depressions of any mountainous country: for example, the Main Caucasus Range, the Kura Lowland.

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

Microforms

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

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

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Classifications of landforms

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

1. Morphological classification taking into account the sizelandforms

Landforms of the Earth

1. Planetary forms are continents, mobile belts, ocean floors 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 medium-sized forms: beams, ravines;
5. Microforms are irregularities that complicate the surface of mesoforms: karst sinkholes, gullies;
6. Nanoforms are very small irregularities that complicate meso- and microforms: hummocks, ripples on the slopes of dunes, etc.

2. Classification according to genetic characteristics

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) aeolian forms; c) glacial; d) karst, etc.

3. Morphogenetic classification:

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

1. Geotextures;
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 its origin.

In this case, the following stand out:

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

Morphological structures – 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 of 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. The age of a relief can be understood as certain stages of its development. For example, the formation of a river valley after the retreat of a glacier: 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, and a river floodplain is formed. This is the maturity stage of the valley. Due to lateral erosion, the floodplain expands, the river flow slows down, and the channel becomes winding.

The old age stage begins in the development of the river valley.

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

Literature.

1. Smolyaninov V. M. General geoscience: lithosphere, biosphere, geographical envelope. Educational manual / V.M. Smolyaninov, A. Ya. Nemykin. – Voronezh: Origins, 2010 – 193 p.

More articles on the topic

Shapes and elements of relief forms

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; the foot of a separate mountain stands out , slopes, peak, which are closely connected with each other).

Based on geometric characteristics, the following relief elements are distinguished:

- edges or surfaces;

- edges - the intersection of two faces;

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

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

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

— subhorizontal surfaces (with inclination angles up to 2°);

— slopes (angles of inclination 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, permafrost), they lose their morphological expression and turn into rounded, smoothed surfaces. The consequence of this is the frequently observed transitions (slope bends) both between the 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, ravine, river valley)

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

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

3. – positive or

- negative.

Identification of positive and negative landforms does not cause difficulties when comparing neighboring simple or relatively simple landforms. Thus, 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 relief form (with gullies, ravines, river valleys), then it will act as a positive relief form in relation to the Oka-Don Plain.

The concept of “positive” and “negative” landforms becomes even more complicated when moving to a comparison of landforms of a higher taxonomic rank.

4. Among the relief forms formed by exogenous processes, there are accumulative(formed by accumulation of material), and denudation(or worked out) landforms formed due to the removal of material (ravine, blowing basin).

The photograph (photo 1) shows a panorama of the village of Inya, in which 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 - large, long)

3. macroforms (makros - large)

4. mesoforms (mesos – middle)

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 (transition zones);

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

Continents are the largest positive landforms on Earth.

Most of them are land; a significant part of the continents participates in the structure of the bottom of the World Ocean. Their most important feature is the composition of the earth’s crust of the continental type.

The ocean bed is the main part of the bottom of the World Ocean, lying, as a rule, at depths of more than 3 km and characterized by the distribution of the oceanic type of crust.

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

- thus, on 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 are the largest mountain system passing through all the oceans and differ 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;

- lowland countries within continents;

- large depressions and uplifts within the ocean floor;

— planetary-scale faults expressed in relief (for example, the San Andreas fault in North America, passing through the city of San Francisco).

Examples of megaforms include the depressions of the Gulf of Mexico and the Caribbean Sea, the mountain systems of the Alps and Caucasus, the West Siberian Plain and the Central Siberian Plateau, and Altai.

3. Macroforms – are components of megaforms. The areas occupied by them are measured in hundreds or thousands, less often tens of thousands of sq. km.

These include, for example, individual ridges and depressions of any mountainous country (North Chuisky, South Chuisky, Katunsky ridges, Chuya Basin, Uimonskaya Basin).

4. Mesoforms are usually measured by several sq. km or tens of sq. km. Examples of such forms are: ravines, ravines, stream valleys, large accumulative forms such as dune chains or moraine ridges.

5. Microforms - These are irregularities that are details of larger shapes. These are, for example, karst sinkholes, erosion potholes, and coastal ramparts.

6. Nanorelief forms are called very small irregularities that complicate the surface of macro-, meso- and microforms.

These are, for example, meadow hummocks, marmots, small erosion grooves, ripple marks on the seabed or on the surface of aeolian landforms.

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

Thus, if planetary relief forms, megaforms, macroforms and some mesoforms were formed as a result of the activity of endogenous processes, then the formation of most mesoforms, as well as micro- and nanoforms, is associated with the activity of mainly 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, is recorded by the visual center of the upper horizontal line.

1.2 saddle- a depression in the ridge located between two hills and two valleys. 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 in 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, is recorded by the visual center of the lower horizontal line.

2)break lines:

sole- a structural line of the relief that limits the base of the slopes of its various forms. It can be horizontal (shown as a horizontal) or inclined (its position is fixed by an imaginary line connecting the places where the horizontals sharply bend).

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

There is a sharp bend in the slope along it. Just like the sole can be horizontal or 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 and dry ditches. In other cases, it is fixed by an imaginary line connecting the places where the horizontal lines sharply bend as they pass from one slope to another.

watershed- a structural line connecting the highest points of two opposite slopes of positive elements and landforms. It is fixed by an imaginary line connecting the places where the horizontal lines sharply bend as they pass from one slope to another. The watershed is the axial line of such relief elements as a ridge, edge, and lintel.

The totality of the above points and lines is relief skeleton.

3) simple spatial elements:

tubercle - an isolated conical or dome-shaped elevation with a clearly defined plantar line. Hillock - higher than 10 meters, hillock - below 10 meters, micro-hillock - non-scale in size in plan.

ridge- a narrow, elongated hill with steep slopes, a flat or rounded top and a sharply defined bottom line.

projection- an elevation on a slope, the transverse profile of which has a slight slope towards the general slope of the surface. A characteristic feature of the protrusion is 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 summit surface on the slope.

terrace - a horizontal or inclined platform extended along the slope. In the transverse profile, its surface is horizontal or slightly inclined. The dimensions of the terrace along the slope significantly exceed its dimensions across it.

pit- a round or oval depression with a sharply defined edge.

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

passage- 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 that completes two adjacent slopes and is limited at the ends by ledges or ribs descending to it. May be horizontal or slightly inclined.

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

ravine- an elongated depression of insignificant length, open towards the general slope of the surface, having steep, unturfed slopes on three sides. Hollows and gullies, the mouth of which is located above the base of the slope, are called hanging.

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

break- a steep, unturfed earthen slope. The height of a cliff is determined not by the length of the strokes in its sign, but by the number of horizontal 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.

Negative landforms

Positive landforms

History of the formation of the region's relief.

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

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

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

3. Post-glacial - as a result of the destruction and accumulation of surface waters.

The flat appearance of the Russian platform and along with it the territory of the region acquired 500 million years ago as a result of the denudation (destruction) of the ancient Karelide Mountains.

Subsequent destruction occurs under the influence of tectonic movements. To the beginning of determination in the region. a highly dissected relief was formed.

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

As a result of erosion-accumulation activity, the appearance of the region. changes radically.

Territory of the region was covered with a thick layer of new rocks. The relief was leveled. Many preglacial 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 ice melted, and flowing lakes formed.

Geologists have established that the territory of the region. in the Quaternary period it was subject 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 thickness of Quaternary deposits dates back to the Dnieper glaciation. Widespread throughout the region. landforms associated with the activity of melted glacial waters. Water flows created hollows, outwash plains, etc.

In the last period, there has been a tendency for a general rise in the region's territory. 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.

Mounds and manes have a relative height of 1 to 10 m

Hills have a relative height of 10 to 100 m

The ridges are comparable in relative height to 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 relief forms.

Closed:

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

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

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

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

- basins characterized by the same depth as lowlands, but similar to depressions, they have steep or relatively steep slopes and a flat bottom or with individual irregularities.

Semi-closed:

- hollow

- dell

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

Unclosed:

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

Anthropogenic factors (deforestation, etc.) have a great influence on the relief.

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

He studies the origin of the relief, the history of its development, internal structure and dynamics. geomorphology(from Greek ge - Earth, morphe - form, logos - teaching).

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

Landforms are made up of landforms. Relief elements– individual parts of relief forms: surfaces (edges), lines (edges), points, angles together forming relief forms. Among the external features of landforms is the degree of their complexity. On this basis they distinguish simple And complex forms. Simple forms (hillock, hollow, hollow, etc.) consist of individual morphological elements, the combination of which forms the form. For example, a hillock has a base, slopes and top. Complex forms consist of a number of simple ones. An example would be a valley, which includes slopes, floodplains, riverbeds, etc.

Based on the slope, surfaces are divided into subhorizontal with a slope of less than 2 0 and inclined surfaces (slopes) with large slopes. Slopes can have different shapes and be straight, concave, convex, stepped. Surfaces can be smooth, convex and concave. Along strike - closed and open. Based on the degree of surface dissection, flat and mountainous areas are distinguished.

The combination of relief forms that have a similar origin and are naturally repeated in a certain space forms type of relief. On larger areas of the earth's surface, it is possible to combine individual types of relief based on their similar origin or differences. In this case they talk about groups of relief types. Since relief types are combined based on their origin, they speak of genetic relief types.

The two most common types of landforms are mountainous and flat. By height, plains are divided into depressions, lowlands, hills, plateaus and plateaus, and mountains into low, medium, high and highest.

Based on the size of the relief forms, they are divided into planetary forms, with an area of ​​millions of km 2 with a height range of 2.5-6 thousand m - these are continents, geosynclinal belts, the ocean floor, MORs. Megaforms– an area of ​​hundreds and thousands of km 2 with a height range of 500-4000 m – these are parts of planetary forms – plains and mountainous countries. Macroforms– an area of ​​hundreds of km2 with a height range 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 range of 200-1000 m – these are, for example, large beam systems. Microforms with an area of ​​up to 100 m2 and a height range of up to 10 m - these are gullies, karst sinkholes, suffosion saucers, dunes, etc.). Nanoforms with an area of ​​up to 1 m2 and a height range of up to 2 m - these are marmots, smallest depressions, hummocks, etc.).

According to the morphogenetic classification, all landforms are divided into geotextures– irregularities formed under the influence of endogenous forces – continental ridges and ocean basins, morphostructures- unevenness formed under the influence of endogenous and exogenous forces, with the leading ones being 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 seas and oceans, which are characterized by: slight fluctuations in heights (up to 200 m) and a slight slope of the terrain (up to 5°). Depending on the absolute heights, they are distinguished: low-lying (up to 200 m); elevated (200-500 m); mountainous or high (more than 500 m) plains.

A mountain is a positive landform that rises above a relatively flat area by at least 200 m. The mountain is limited on all sides by slopes. The transition from slopes to plain is base of the mountain. The highest part of the mountain is its vertex.

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

Mountains – These are highly dissected areas of the earth's surface, raised high above the ocean level. Moreover, the mountains have a single base, rising above the adjacent plains, and consist of many positive and negative landforms. The heights are divided into low mountains up to 800 m, mid mountains – 800-2000 and high mountains – more than 2000 m.

The age of the relief can be: absolute - determined on a geochronological scale; relative - the formation of a relief is established earlier or later than some 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 during 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 source of energy for endogenous processes is the thermal energy of the 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 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 intensities in time and space. According to the direction relative to the Earth's surface, vertical and horizontal movements are distinguished; 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) that separate plates are usually found on the ocean floor, where the Earth's crust is thinnest (5-7 km). Magma rises along faults and, as it hardens, 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 speed of 1-12 cm/year. Their moving apart leads to a collision with neighboring plates, or to immersion (underwater) 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 topography of the Earth are associated with a decrease in the speed of its rotation as a result of the braking effect of the Moon. The stresses arising in the body of the Earth in this case cause deformation of the earth's crust and movement of lithospheric plates.

Vertical movements of lithospheric plates are caused by the fact that mountains composed of lighter rocks have a thicker crust, while 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 load, for example, the formation of ice cover, leads to the “pressing” of the earth's crust into the mantle. So Antarctica dropped by 700 m, and in its central parts the land was lower than the Ocean. The same thing happened in Greenland. The release of the glacier leads to an uplift of the earth's crust: the Scandinavian Peninsula is now rising at a rate of 1 cm/year. 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 black earth region, the area of ​​the Central Russian Upland rises by 4-6 mm/year, and the Oka-Don Lowland decreases 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 layers without violating their integrity and discontinuous, where, as a rule, crustal blocks move in vertical and horizontal directions. Both types of dislocations are characteristic of the Earth's mobile belts, where mountains are formed. However, folded dislocations are practically absent in the cover of platforms. Dislocations in the mountains are accompanied by magmatism and earthquakes.

Exogenous processes are associated with the supply of solar energy to the Earth, but they occur with the participation of gravity. In this case, rocks are weathered and material moves under the influence of gravity: landslides, landslides, screes, material transfer by water and wind. Weathering is a combination of processes of mechanical destruction and chemical change of rocks. The overall effect of the processes of destruction and transport of rocks is called denudation, which leads to leveling of the surface of the lithosphere. If there were no endogenous processes on Earth, then our planet would have long ago had a completely flat surface. This imaginary surface is called the main level of denudation. In reality, there are many temporary levels of denudation at which leveling processes can fade for some time. The intensity of denudation processes depends on the composition of rocks and climate. The greatest importance in this case is the height of the area above sea level, or the erosion base.

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

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

As can be seen, the relief of the lithosphere surface is the result of the opposition of endogenous and exogenous processes. The former create uneven terrain, and the latter smooth them out. During relief formation, endo- or exogenous forces may predominate. In the first case, the height of the relief increases - this is an upward development of the relief. In the second, positive relief forms are destroyed and the depressions are filled. This is its downward development.

The shape of the relief is a distortion of the surface of the lithosphere. Landform is a unit of geomorphology.

Basic landforms

Despite the wide variety of unevenness of the earth's surface, the main forms of relief can be distinguished: mountain, basin, ridge, hollow, saddle.

Classification

Landforms vary:

• by size (planetary landforms, megalandforms, macrolandforms, mesolandforms, microlandforms, nanolandforms);
• by origin (tectonic, volcanic, water-erosive, glacial, karst, aeolian, etc.);
• by age and other characteristics;
• by shape (positive landforms, negative landforms).

Planetary landforms

• Geosynclinal belts
• ocean bed
• Mid-ocean ridges

Mega landforms

• Gulf of Mexico Trench,
• trench of the Caribbean Sea,
• Alps mountain system,
• mountain system of the Caucasus,
• Deccan plateau.

Macro relief forms

Individual ridges and depressions of a mountainous country. Examples: Main Caucasus Range, Bzyb Range (Abkhazia)…

Mesoforms of relief

Examples: ravine, ravine, stream valley, cave, mountain range, large accumulative forms such as dune chains….

Microforms of relief

Examples: sinkhole, grotto, well, erosion pothole, coastal rampart...

Nanoforms of relief

Examples: molehill, meadow tussock, surchin, small erosion grooves, ripple marks on the surface of aeolian forms or on the seabed.

Methods of depicting relief

The method of depicting the relief should provide a good spatial understanding of the terrain, reliable determination of the directions and steepness of slopes and marks of individual points, and the solution of various engineering problems. Since the existence of geodesy, several methods have been developed for depicting relief on topographic maps. Let's list some of them:

• Washing method. Hillshade is a plastic halftone image of a relief by applying shadows. Hillshading is usually used with side lighting, where the light source is in the upper left corner of the card; http://dic.academic.ru
• Hatching method. This method is used in many 19th century engravings. The thickness of the strokes and the distances between them depend to a certain extent on the steepness of the slopes.
• Marking method. With this method, marks of individual terrain points are marked on the map.
• Contour method.
• Method of layer-by-layer painting. This method is used on small-scale maps. The Earth's surface is shown in brown: the larger the marks, the thicker the color. The depths of the sea are shown in blue or green: the greater the depth, the deeper the color.

Currently, on topographic maps, the method of contours is used in combination with the method of marks, and on one square decimeter of the map, as a rule, at least five point marks are labeled.

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