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 northern-western 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.

Classifications of landforms

There are several classifications of landforms of the Earth, having different bases. According to one of them, two groups of relief forms are distinguished:

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

The classification of landforms of the Earth by size is presented in Table. 1 and in Fig. 1.

Table 1. Landforms of the Earth by size

Rice. 1. Classification of the largest landforms

Let us separately consider the relief forms characteristic of the land and the bottom of the World Ocean.

Relief of the Earth on the World Map

Landforms of the ocean floor

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

Mainland Shoal- the coastal part of the seas and lying between the coast and the continental slope. This former coastal plain is expressed in the topography of the ocean floor as a shallow, slightly hilly plain. Its formation is mainly associated with the subsidence of individual land areas. This is confirmed by the presence within the continental shallows of underwater valleys, coastal terraces, fossil ice, permafrost, remains of terrestrial organisms, etc. Continental shallows are usually distinguished by a slight bottom slope, which is practically horizontal. On average, they decrease from 0 to 200 m, but within their limits there can be depths of over 500 m. The relief of the continental shallows 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 coastlines.

Rice. 2. Relief forms of the ocean floor

Continental slope - the inclined surface of the bottom of the seas and oceans, connecting the outer edge of the continental shallows with the ocean bed, extending to a depth of 2-3 thousand m. It has fairly 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 of greater magnitude, almost vertical slopes - cliffs. Steep continental slopes lead to the fact that in areas of maximum bottom inclination, masses of loose sediments slide to the depths under the influence of gravity. In these areas, a bare slope or muddy bottom may be found.

The relief of the continental slope is complex. Often the bottom of the continental slope is cut by narrow deep gorges-canyons. They are often found near steep rocky shores. But there are no canyons on continental slopes with a gentle bottom slope, as well as where there are stumps of islands or underwater reefs on the outer side of the continental shallows. The tops of many canyons are adjacent to the mouths of existing or ancient rivers. Therefore, canyons are considered as an underwater continuation of flooded river beds.

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

ocean bed- the main space of the bottom of the World Ocean with prevailing depths of more than 3000 m, extending from the underwater edge of the continent 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 stock has slight angles of inclination, on average they are 20-40°.

The relief of the ocean floor is no less complex than the relief of the land. The most important elements of its relief are abyssal plains, oceanic basins, deep-sea ridges, mid-ocean ridges, hills and submarine 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 the Southern Hemisphere at 40-60° S. w. Three ridges extending northwards from it extend meridianally in each ocean: the Mid-Atlantic, Mid-Indian and East Pacific. The total length of the mid-ocean ridges is more than 60 thousand km.

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

Abyssal plains- flat surfaces of the 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 undulating with a height range of up to 1000 m. One plain is separated from the other by ridges.

Some of the single 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.

Chains of volcanic islands above a subduction zone, occurring where one oceanic plate subducts beneath another, are called island arcs.

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

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

Landforms

The main landforms on land are mountains and plains.

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

In total, 24% of the earth's surface is mountainous.

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

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

Rice. 3. Classification of mountains by height

The highest mountains of our planet are the Himalayas, examples of high mountains are the Cordillera, Andes, Caucasus, Pamir, middle ones are the Scandinavian Mountains and the Carpathians, low ones are the Ural Mountains.

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

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

• folded - formed as a result of the folding of a thick layer of sedimentary rocks (mainly formed during the Alpine era of mountain building, which is why they are called young mountains) (Fig. 4);
• blocky - formed as a result of the rise of hard blocks of the earth's crust to a great height; 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-block mountains are old folded mountains that were largely destroyed, and then, in new periods of mountain building, individual blocks of them were again raised to great heights (Fig. 6).

Rice. 4. Formation of folded mountains

Rice. 5. Formation of old (block) mountains

Based on their location, epigeosynclinal and epiplatform mountains are distinguished.

Based on their origin, mountains are divided into tectonic, erosional, and volcanic.

Rice. 6. Formation of folded-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 types of faults).

Erosion mountains - highly elevated plateau-like regions 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 sheets, distributed over a large area and usually superimposed on a tectonic base (on a young mountainous country or on ancient platform structures, such as the volcanoes of Africa). Volcanic cones are 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, Misti in Peru, Shasta in California, etc. Heat cones They have a structure similar to volcanic cones, but are not so high and are composed mainly of volcanic scoria - 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 ranges, mountain ranges and uplifts of a smaller rank are distinguished.

mountain range called a linearly elongated positive form of relief, formed by large folds and having a significant extent, mostly 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- a collection of mountain ranges, chains, formed during one geotectonic epoch and having spatial unity and a similar structure, uplands(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 era, but having different structure and appearance.

Mountain belt- the largest unit in the classification of mountainous relief, corresponding to the largest mountain structures, united spatially and according to the history of development. Usually the mountain belt extends 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 formation diagram of the plains is shown in Fig. 7.

Rice. 7. Formation of plains

Depending on the height among the plains, the land is divided into:

• lowlands - having an absolute height from 0 to 200 m;
• elevations - no 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 or inclined. Depending on the nature of the mesorelief complicating the surface of the plain, flat, stepped, terraced, wavy, ridged, hilly, hilly and other plains are distinguished.

Based on 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 pre-existing terrain irregularities, and accumulative, resulting from the accumulation of thick layers 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 divided into volcanic, marine, alluvial, lacustrine, glacial, etc. Accumulative plains of complex origin are also common: lacustrine-alluvial, deltaic-sea, alluvial-proluvial.

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

Land occupies only 29% of the Earth's surface, which is 149 million km 2. The bulk of the landmass is concentrated in the Northern Hemisphere.

The average height of the Earth's land is 970 m.

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

The average depth of the ocean is 3704 m. The topography of the bottom of the World Ocean is dominated by plains. Deep-sea trenches and trenches account for only about 1.5% of the ocean's area.

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, which generally have a flat shape, despite some greater or lesser unevenness on the surface. 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).

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 form. 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 height 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 landforms in relation to the horizon plane, positive (convex in relation to the horizon plane) and negative (concave) landforms 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;

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.

The 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, and 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 Taganay (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, 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.

7. Selection of landforms and generalization of contours

It is recommended to make the largest number of profiles when compiling maps of mountainous areas.
Any deviation of the earth's surface from the level is called irregularities. Individual irregularities in the earth's surface that have a certain appearance are called landforms. Every form of relief is limited by surfaces, lines and points, which are called relief elements. Examples of relief elements include slopes, thalwegs, peaks, etc.

Based on external features, relief forms can be classified in relation to the horizon plane or by the size of the forms. In relation to the horizon plane, positive and negative relief forms are distinguished. The former have a convex surface, protruding over the surrounding area, while the latter have a concave surface, forming depressions in the surrounding area.

Based on size, there are large (macro), medium (meso) and small (micro) landforms. Exact criteria for classifying certain forms as large, medium or small have not yet been developed. Typically, large forms include mountain ranges, individual mountains, large valleys, etc.; to the middle ones - spurs of mountain ranges, individual hills, small valleys, etc.; to small ones - mounds, depressions, etc., i.e., such shapes that are measured in units and fractions of meters.

Dividing shapes by size is important for cartography. Maps of small scales (1: 500000-I: I 000000) mainly depict only large landforms. Medium-scale maps (1: 100,000-1: 200,000) depict both large and medium-sized landforms. On large-scale maps, small shapes can also be depicted with contours.

Positive landforms

Positive forms of relief include: mountain, mountain range, hill, ridge.

A mountain is an elevation of a relative height of more than 200 m, with clearly defined slopes and foot (base), rising in isolation above the surrounding area (Fig. 14a). The highest part of the mountain is called the summit. The tops are flat (Fig. 146), pyramidal (Fig. 14c), peaked (Fig. 14d), cone-shaped (Fig. 14e) and dome-shaped (Fig. 14e).

A collection of closely located mountains is called a mountain group.

A mountain range is a linearly elongated hill with a relative height of more than 200 m, with clearly defined slopes and foothills. The highest part of the ridge is called the crest. The lower parts of the ridge are called saddles. Saddles used as communication routes between opposite slopes of a ridge are called passes.

Based on the steepness of the opposite slopes, symmetrical and asymmetrical ridges are distinguished. The former have slopes of approximately the same steepness, while the latter have one slope steeper than the other.

A ridge that is small in length and height is often called a mountain range or ridge. A linearly elongated system of mountains or ridges is called a mountain range.

Often, side ridges called spurs extend from the main ridges at different angles. In some cases, two or more ridges converge. The junction of the ridges is called a mountain junction.

A hill is a rounded elevation with a relative height of less than 200 m and mostly with gentle slopes of average steepness and an unclearly defined foot (Fig. 15). In mountainous areas there are hills with sharp peaks and steep, even rocky slopes.
Uval is a linearly elongated hill with a relative height of less than 200 m, with gentle slopes of average steepness and an unclearly defined foot. A narrow ridge with a clearly defined foot is often called a hilly ridge.

Rice. 15. Hilly terrain

Negative landforms

Negative forms of relief include valleys (and their varieties - ravines and gullies) and basins.

A valley is a linearly elongated depression of terrain with a slope in one direction. The sizes and outlines of valleys can be very different.

Valleys differ in the shape of the transverse profile, depth, position in the relief (longitudinal, transverse) and the nature of the upper reaches (closed, semi-open and open). The cross profile of a typical river valley is shown in Fig. 16. The lowest, relatively flat part of a valley is called its bottom or bed (B, D"). Rivers flow along the bottom of most valleys. The part of the valley bottom occupied by a river is called a channel (3), and flooded by river waters during floods is called a floodplain
Rice. 16. Cross profile of a river valley
(Zh, Zh") - The bottom of the valley is limited on the sides by slopes (BV, B"D"). Often the slopes are stepped and consist of alternating flat areas and ledges. More or less flat platforms (VG, DE, D" E") , stretched along the valley and separated from each other by ledges (GD, EZH, E "ZH") are called terraces.
The width of the valley is taken to be the width of its bottom. The depth of the valley is the height of the upper bend of the slope above the lower part of the bottom.

A ravine is a short, but relatively deep and narrow erosional depression, resembling the Latin letter V in cross-section, with steep or steep slopes.

Gullies are formed on steep and high slopes of valleys as a result of the eroding activity of periodic water flows. The average depth of the ravines is 10-20 m, width 20-40 m and more. In the steppe and forest-steppe zones they form a dense
network, reaching in places 50 m in depth and several kilometers in length.

There are bottom ravines, cutting into the bottom of gullies (Fig. 17), and lateral, cutting through the slopes of gullies and river valleys (Fig. 18), as well as hanging ravines, the mouth of which is located above the bottom of the valley into which they flow (Fig. 19).
Beams, unlike ravines, are larger erosional depressions in size (Fig. 20). The depth of their incision can be measured in several tens of meters. The bottom is quite wide, level, with a shallow channel without a constant watercourse; the slopes are long, gentle, becoming steep only where they are washed away by a periodically appearing watercourse; the top is usually limited by the edge.

A basin is a closed depression of terrain of various sizes. In the basin there is a bottom - the lowest, more or less pink part, and slopes - side slopes converging to the bottom from all sides. Deep and extensive basins, the bottom of which falls below sea level, are called depressions.
Among other negative forms, noteworthy in lowland countries are small flat and shallow rounded depressions, which are called depressions or saucers. They are formed, as a rule, as a result of soil subsidence; their depth rarely exceeds 1 m, their diameter ranges from 50-100 m.
In mountainous countries, there are depressions of a spherical shape, with an exit in one direction, called carts (circuses). They are formed by the activity of glaciers. Their depth is tens and hundreds of meters.