Height of various landforms. Landform types and their origin

terrain is a set of irregularities in the earth's surface. The terrain is divided into convex and concave irregularities of various shapes and sizes. But despite this, these irregularities can be divided into five types of relief surfaces: mountains, ridges, hollows, basins and saddles.

Mountain represents a hill with a shape resembling a cone. The mountain has a top, from which the relief goes down to the base of the sole.

Ridge is a hill that extends in one direction. The ridge has a watershed line - a line connecting opposite slopes of the ridge.

Basin is a closed cavity. The hollow has a relief shape opposite to the mountain. The hollow has the lowest point - the bottom. Lakes and swamps often appear at the bottom.

dell is a relief form opposite to the ridge - a depression, elongated in one direction. As a rule, the hollows are covered with turf, shrubs.

Saddle represents a depression between two peaks. In the mountains, through the ridges along the saddles, there are paths, also called passes.

1 - mountain, 2 - hollow, 3 - ridge, 4 - hollow, 5 - saddle, 6 - ledge

The relief image on topographic maps is carried out in three ways: contour lines, hillshade and hypsometric. The hypsometric and hillshade method is a designation of heights using color shades depending on height and is used on maps with a scale starting from 1: 500000. The most common method is a method of drawing contour lines, which indicate unevenness of the relief, having the same height. The direction of the contour slope is indicated by a dotted line with an arrow at the end, i.e. for example, if a mountain is indicated, then the arrow will be directed in the opposite direction from the top towards the bottom.

In addition to the arrow indicating the direction of the slope, it can also be determined by other signs. According to the elevation marks, it is obvious that the slope will be directed from a higher point to a lower one. According to the contour lines - the top of the figures of the contour lines is directed to the heights of the ridges and mountains, i.e. in the opposite direction from the direction of the slope. On lakes, rivers and streams - water flows down to the lowest places, therefore the direction of the slope will be directed towards water bodies.

The distance between two contour lines is called relief section height. Standing Every fifth contour line is made bolder to make it easier to read the terrain. The closer the horizontals are to each other, the steeper the slope. On topographic maps with a scale of 1:25000, horizontal lines are drawn every 5 meters, 1:50000 - every 10 m, 1:100000 - every 20 m. The zero horizontal is the average level of the Baltic Sea.

Determination of slope slope.
The distance between two contour lines on a map is called laying, which shows the steepness of the slope. The easiest way to determine the steepness is by using a ruler or by eye. To do this, you need to know that on the maps of Russia the standard height of the section for any scale is such that a laying of 1 cm is equal to a slope of 1 °. Therefore, how many times the laying on the map is less than 1 cm, then so many times the steepness of the slope is greater than 1 °, and vice versa.

For example, the laying on the map is 2 mm, that is, five times less than 1 cm, therefore the steepness is five times greater than 1 °, namely 5 °.

Relief(fr. relief, from lat. relevo- raise) - a set of irregularities of the solid earth's surface and other solid planetary bodies, diverse in shape, size, origin, age and history of development. It is made up of positive and negative forms. The relief is an object of study of geomorphology.

mountain, hill - a convex cone-shaped form of relief, towering above the surrounding area. The highest point of a mountain or hill is called summit . From the summit, slopes or slopes run in all directions; the line of transition of the slopes into the surrounding plain is called sole . A mountain differs from a hill in the size and steepness of its slopes; at a height above the surrounding area up to 200 m, a similar relief form with gentle slopes is called a hill, and more than 200 m with steep slopes is called a mountain. Mountains and hills are depicted as closed horizontal lines with berghashes directed from the top to the bottom.

Basin (hollow) - the opposite of a mountain (hill) relief form, representing a bowl-shaped depression of the earth's surface. The lowest point of the basin is called the bottom. The lateral surface of the basin consists of slopes; the line of their transition to the surrounding area is called the edge. The hollow, like the mountain, is depicted as closed horizontal lines, but in this case the berghash lines are directed towards the bottom.

Ridge - an elongated and gradually lowering hill in one direction. A ridge is usually an offshoot of a mountain or hill. The line connecting the highest points of the ridge, from which the slopes depart in opposite directions, is called the watershed. The ridge is depicted by convex horizontal lines directed by a convexity in the direction of lowering the terrain.

dell- a deepening of the earth's surface elongated in one direction with a gradually lowering bottom. Two slopes of the hollow, merging with each other in its lowest part, form a spillway line or thalweg. The types of hollows are: d Olina - a wide hollow with gentle slopes;

ravine- (in a mountainous area - a gorge) - a narrow hollow with steep bare slopes;

beams is called larger than ravines, depressions with gentle slopes, often covered with vegetation.

The hollow is depicted by concave horizontal lines, directed by concavity towards the lowering of the terrain; the steep slopes of the ravine are depicted by special conventional signs.

Saddle - a low area located on a ridge between neighboring peaks. Two hollows originate from the saddle, spreading in opposite directions. In mountainous areas, saddles serve as communication routes between opposite slopes of the ridge and are called passes . The saddle is depicted by horizontals, facing bulges towards each other.

8 ways to depict terrain

1. Picture (perspective) method. In this way, the relief was depicted on a hundred
ry maps in the form of primitive drawings of hills, mountains, ranges. Relief depicted
Xia as he was seen. For greater clarity, the mountains were covered with shadows. This method of depicting relief was widespread in the 18th-18th centuries. In on
standing time, this method is used on those maps where visibility is required, and not
accuracy, and therefore it is primarily used on children's cards.

2. 2. Stroke method. Picture image of the relief in the XVIII century. primarily
ceased to satisfy the military, the main consumers of cards. They had to quickly
get an accurate idea of the steepness of the slopes, the ruggedness of the terrain,
the nature of the relief as a whole. Therefore, a new way of depicting relief was proposed -
dashed. In Russia, the A.P. Bolotov and the scale of the General Staff. Prin
The scheme for constructing such scales is as follows: the steeper the slope, the thicker and denser the hatching,
at the same time, steep slopes are covered with a shadow, and gentle slopes are highlighted (Fig. 5.14).

The disadvantage of this method was that it is impossible to determine the abso
fierce and relative heights. In addition, drawing strokes is very laborious, and printing
map making requires high reproduction technique. So we started looking for new ways
relief images. Currently, this method is used when depicting rocks.
stogo relief on topographic maps.

3. Hillshade method (black and white plastic), i.e., the creation of halftone iso
fermentation under given illumination of the area. Washing is used to give volume
sti landforms.

Hillshade was widely used on handwritten maps already in the second half of the 18th century,
but its seal was mastered only in the middle XIX in. as a result of the introduction of lithography. Ori
hillshade genal is like a photograph of a relief model locally
sti under side northwest lighting

4 Elevation method. Elevation marks are absos signed on the map.
fierce marks of heights of points. With the help of elevation marks, characteristic heights are shown.
you, including command, having the greatest height, from which the possibility is realized
good view of the area. Altitude marks of mountains, hills, barrows, passes, about
ditches and ledges, embankments and recesses. They make it easier to read the map and make it possible to identify
for determining the excesses of some points over others.

5. -
heights.
solid (carried out according to
vein to the height of the section); thickened
additional horizontal or semi-mountain
umbrellas auxiliary horizontal
(carried out at a quarter of the height of the relief section).

6. hypsometric method, or layer-by-layer coloring of steps of heights, the main and most
a more used way of depicting relief on physical and hypsometric maps.
Contours on overview maps are called isohypses. isohypses serve as dividing
lines between steps of heights passing through a certain number of meters along
height. On hypsometric maps of Russia, a scale is used, which is built according to the principle
qipu: the higher the darker (Fig. 5.17).

10 depiction of the main landforms of the terrain with horizons

Horizontal method. Horizontal - is a line connecting like marks
heights. Contours - the main way to depict relief on topographic maps
(Fig. 5.16). There are the following types of horizontals: solid (carried out according to
vein to the height of the section); thickened (with a cross section of 5.0 m and 20 m, every fifth th
rizontal, with a section of 2.5 m - every tenth); additional horizontal or semi-mountain
umbrellas (carried out at half the height of the relief section); auxiliary horizontal
(carried out at a quarter of the height of the relief section). The horizontals are supplemented with berghstries (short dashes perpendicular to
to the horizontals indicating the direction of the slope), the signatures of the marks of absolute heights
characteristic points of the terrain and some contour lines (marks are signed in their time
ditches and the base of the numbers are always located down the slope). The main advantage
of this method is that horizontally it is possible to carry out various cartometry
scientific work: to determine the absolute heights of points and the excess of one point over another
mi, steepness and direction of slopes, etc. According to the pattern of contour lines, their shape, density
reference, you can get an idea of the terrain. The right height
that section of the relief on the map allows you to very clearly convey the nature of the relief and the degree
its dismemberment. Therefore, this method is now used on state topographers.
physical cards.

Contour properties

Contour properties:

1. All points lying on the same horizontal line have the same elevation

2. Contours with different elevations do not intersect

3. The steeper the slope, the smaller the distance between contour lines

The marks of the contour lines are signed in their break so that the lower part of the number is facing the direction of the slope decrease; berg-strokes are used to determine the direction of the slope. Every fifth horizontal line is drawn with a thickened line.

Relief section height (h)- they call the difference in elevations of adjacent contour lines - this is a constant value for this drawing.

Horizontal distance between adjacent horizontals - slope laying (d) .

Slope (i) is tg of the terrain slope ν or the ratio of the height difference of the points to the horizontal distance between them.

The structure of the earth's surface is very diverse. However, it is always possible to find forms that are similar in appearance and origin, which are regularly repeated in a certain territory and are typical for it. Such combinations of forms of the earth's surface that are homogeneous in appearance and origin are called relief types.

The main external features of the relief: the nature of its forms, height above sea level and the relative height or depth of dissection. According to these indicators, the relief is flat, hilly and mountainous.

Plains called areas in which the fluctuations in heights and slopes of the surface are very small.

Plains are: oblique- with a slight slope to one side; concave- with an inclination from all sides to the middle; and wavy- with fluctuations in inclination, then in one direction, then in the other direction and alternating flat elevations and elevations of the surface.

According to the height above sea level, the following plains are conditionally distinguished:

– base- with an absolute height of up to 200 m;

– sublime(plateau) - with heights up to 500 m;

– upland- with altitudes over 500 m.

hilly they call a relief with relative heights up to 200 m. Hills often have the form of elongated ridges or ridges and, accordingly, form a ridge or hilly relief. Depending on the height of the hills, the relief is distinguished coarse-hilly, medium hilly and small hilly.

Mountain a relief is called, the irregularities of which exceed the relative height of 200 m. According to the shape, absolute and relative height, the mountain relief is divided into the following types: alpine(alpine) type, mid-mountain and lowland types.

The morphology of the plain, hilly and mountainous relief is far from exhausted by the above characteristics. It is largely determined by the features of the geomorphological structure of the territory and, above all, by the conditions of occurrence of rocks.

The following four forms of bedding are most characteristic:

undisturbed horizontal occurrence;

slightly disturbed horizontal occurrence - the layers have a gentle and consistent fall;

folded occurrence - layers are crumpled into folds;

fold-fault occurrence - the layers are crumpled into folds and displaced relative to each other.

The nature of the occurrence of layers finds a vivid expression in the forms of relief during their erosional dissection, and especially in those cases where there is an alternation of layers of different density and different resistance to erosion.

Such specific forms of relief, due to the occurrence of layers of different densities, i.e. geological structure are called structural.

Under conditions of undisturbed horizontal occurrence of layers, erosional dissection forms watershed elevations (plateaus, plateaus). The slopes of the hill are often stepped, each step corresponds to the exit to the surface of a solid layer.

Under conditions of weakly disturbed layers during erosional dissection, in places where dense layers emerge, characteristic structural relief forms are formed, called cuestami. They are usually separated by valleys embedded in softer, more easily eroded rocks. Cuesta usually have an asymmetrical structure.

Under conditions of folded occurrence, with the alternation of regular folds of a convex (anticline) and concave (syncline) shape, erosional dissection most often forms anticlinal ridges with a wide rounded ridge, monoclinal ridges with a sharp ridge and an asymmetric transverse profile; longitudinal synclinal valleys with a symmetrical transverse profile; asymmetric monoclinal valleys.

Under the conditions of folded-faulting occurrence of layers, in addition to the listed relief forms, there are also forms that were formed as a result of vertical displacements of layers (uplifts and subsidence) with gaps between them. Are formed horsts and grabens. The latter in the mountains are usually occupied by rivers and lakes, contoured by small steps and slopes with ledges.

Thus, the geological structure of the area determines the formation of various and widespread structural forms characteristic of various types of relief. From this it follows that even a general idea of the geological structure of the region is of considerable help in assessing the image of the relief on a topographic map.

The relief of the earth's surface is determined not only by the movement of the earth's crust (tectonics) and the nature of the occurrence of layers, but also by the activity of the second group of factors - external (exogenous). The latter significantly transform the primary (tectonic) forms and greatly complicate their structure.

These factors include the activity of water flows (temporary and permanent) of the seas, lakes, glaciers, melted glacial waters, groundwater, wind and others. The activity of these factors is manifested in the fact that in some places the rocks lying on the surface of the Earth are destroyed, eroded and carried out from the given area to another, where they are deposited and, accumulating, often reach great thickness, thus passing through the stages of hypergenesis, sedimentogenesis and diagenesis.

The processes of destruction are called erosion(or more broadly denudation), and accumulations - accumulations. In the process of erosion or denudation, the relief is dissected, the elevations are more and more destroyed and eventually leveled out (the process peneplanization). Such relief is called erosion or denudation.

In the process of accumulation, depressions are filled with loose rocks carried from the side, and a predominantly flat relief, called accumulative, is formed.

In accordance with what factor (agent) produces erosion or accumulation, water-erosion or water-accumulation forms, glacial-erosion and glacial-accumulation forms, etc. are distinguished.

Where the activity of surface and underground waters occurs in soluble rocks (limestones, dolomites, etc.), peculiar voids (karst landforms) are formed.

The flat, hilly and mountainous reliefs described above can be of different origin and, consequently, have different forms.

Plains by their origin are:

– marine accumulative- formed as a result of transgression of the ocean floor;

– river accumulative- are formed as a result of tectonic uplifts and subsidences;

– water-glacial accumulative- formed as a result of melting glaciers;

- lacustrine-accumulative - areas of flat bottoms of former lakes;

- upland accumulative - are formed as a result of the destruction and accumulation of materials;

– volcanic- the result of the activity and destruction of volcanoes;

- residual - the result of denudation of the earth's surface;

- abrasion - the result of the impact of sea waves.

Hilly relief by origin is: water-erosion; glacial erosion; wind and volcanic.

Mountain relief by origin is: erosion-tectonic, erosion (erosion-folded and erosion-block) and volcanic.

SLOPE STEEPENESS

terrain called a set of irregularities of the earth's surface.

Depending on the nature of the relief, the terrain is divided into flat, hilly and mountainous. The flat terrain has mild forms or almost no irregularities at all; hilly is characterized by alternation of relatively small elevations and depressions; mountainous is an alternation of elevations over 500 m above sea level, separated by valleys.

Of the variety of landforms, the most characteristic ones can be distinguished (Fig. 12).

Mountain(hill, height, hill) is a cone-shaped relief form towering above the surrounding area, the highest point of which is called the peak (3, 7, 12). The top in the form of a platform is called a plateau, the peak of a pointed shape is called a peak. The lateral surface of the mountain consists of slopes, the line of their confluence with the surrounding area is the sole, or base, of the mountain.

Rice. 12. Characteristic landforms:

1 - hollow; 2 - ridge; 3,7,12 - peaks; 4 - watershed; 5.9 - saddles; 6 - thalweg; 8 - river; 10 - break; eleven -

Basin or hollow,- This is a recess in the form of a bowl. The lowest point of the basin is the bottom. Its lateral surface consists of slopes, the line of their confluence with the surrounding area is called the edge.

Ridge 2 - this is a hill, gradually lowering in one direction and having two steep slopes, called slopes. The axis of the ridge between the two slopes is called the watershed line or watershed 4.

dell 1 - this is an elongated depression of the terrain, gradually lowering in one direction. The axis of the hollow between two slopes is called a weir line or thalweg 6. The varieties of the hollow are : valley- a wide hollow with gentle slopes, as well as ravine- a narrow hollow with almost steep slopes (cliffs 10) . The initial stage of a ravine is a ravine. A ravine overgrown with grass and shrubs is called beam. Sites sometimes located along the slopes of hollows, having the form of a ledge or steps with an almost horizontal surface, are called terraces 11.

Saddles 5, 9 are the low parts of the terrain between the two peaks. Roads often pass through saddles in the mountains; in this case the saddle is called pass.

The top of the mountain, the bottom of the basin and the lowest point of the saddle are characteristic points of the relief. The watershed and thalweg are characteristic lines of relief. The characteristic points and lines of the relief facilitate the recognition of its individual forms on the ground and their depiction on the map and plan.

The method of depicting the relief on maps and plans should make it possible to judge the direction and steepness of the slopes, as well as determine the marks of points in the terrain. However, it must be visible. There are various ways of depicting relief: perspective, shading with lines of different thicknesses, color wash(mountains are brown, hollows are green), horizontal. From an engineering point of view, the most advanced methods of depicting a relief are horizontals in combination with signatures of characteristic points marks (Fig. 13) and digital.

Horizontal A line on a map that connects points of equal elevation. If we imagine a section of the Earth's surface by a horizontal (level) surface R 0 , then the line of intersection of these surfaces, projected orthogonally onto a plane and reduced to a size on the scale of a map or plan, will be a horizontal line. If the surface R 0 located at a height H from the level surface, taken as the origin of the absolute heights, then any point on this horizontal line will have an absolute elevation equal to H. The image in the relief contours of the entire area can be obtained as a result of the section of the surface of this area by a number of horizontal planes R 1 , R 2 , … R n , located at the same distance from each other. As a result, contour lines with marks are obtained on the map H + h, H + 2h etc.

Distance h between secant horizontal planes is called relief section height. Its value is indicated on a map or plan under a linear scale. Depending on the scale of the map and the nature of the depicted relief, the height of the section is different.

The distance between contour lines on a map or plan is called mortgage. The greater the laying, the less the steepness of the slope on the ground, and vice versa.

Rice. 13. Image of the terrain with contour lines

Contour property: contour lines never intersect, with the exception of an overhanging cliff, natural and artificial funnels, narrow ravines, steep cliffs, which are not displayed by contour lines, but are indicated by conventional signs; horizontal lines are continuous closed lines that can only end at the border of a plan or map; the thicker the horizontal, the steeper the terrain depicted, and vice versa.

The main relief forms are depicted by horizontal lines as follows (Fig. 14).

Images of the mountain and the basin (see Fig. 14, a, b), as well as a ridge and a hollow (see Fig. 14, c, g) are similar to each other. To distinguish them from each other, the direction of the slope is indicated at the horizontal. On some horizontal lines, marks of characteristic points are signed, and so that the top of the numbers is directed towards the rise of the slope.

Rice. 14. Image by contour lines of characteristic

landforms:

a - mountain; b - basin; c - ridge; G- hollow; d- saddle;

1 - top; 2 - bottom; 3 - watershed; 4 - thalweg

If, at a given height of the relief section, some of its characteristic features cannot be expressed, then additional semi- and a quarter of the horizontal are drawn, respectively, through half or a quarter of the accepted height of the relief section. Additional horizontals are shown with dotted lines.

To make it easier to read the contour lines on the map, some of them are thickened. With a section height of 1, 5, 10, and 20 m, every fifth horizontal line is thickened with marks that are multiples of 5, 10, 25, 50 m, respectively. With a section height of 2.5 m, every fourth horizontal line is thickened with marks that are multiples of 10 m.

The steepness of the slopes. The steepness of the slope can be judged by the magnitude of the deposits on the map. The smaller the laying (distance between horizontals), the steeper the slope. To characterize the steepness of the slope on the ground, the angle of inclination ν is used. Vertical angle called the angle enclosed between the line of the terrain and its horizontal laying. The angle ν can vary from 0º for horizontal lines to ± 90º for vertical lines. The greater the angle of inclination, the steeper the slope.

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

The top of the mountain, the bottom of the basin, the point of the saddle are characteristic points of the relief; the line of the watershed of the ridge, the line of the spillway of the hollow, the line of the foot of the mountain or the ridge, the line of the crest of the hollow or hollow are the characteristic lines of the relief.

Classification

Landforms vary:

Planetary landforms

Geosynclinal belts
mid-ocean ridges

Mega landforms

Relief macroforms

Separate ridges and depressions of any mountainous country Examples: Main Caucasian ridge, Bzyb ridge (Abkhazia) ...

Mesoforms of relief

relief microforms

Nanoforms of relief

Examples: meadow tussock, marmot, fine erosion grooves, ripple marks on the surface of aeolian forms or on the seabed.

Relief imaging methods

The method of depicting the relief should provide a good spatial representation of the terrain, reliable determination of the directions and steepness of slopes and marks of individual points, and the solution of various engineering problems.

During the existence of geodesy, several methods have been developed for depicting relief on topographic maps. We list some of them:

promising way.
Washing method. This method is used on small scale maps. The surface of the Earth is shown in brown: the larger the mark, the thicker the color. The depths of the sea are shown in blue or green: the deeper the depth, the thicker the color.
Shading method.
Marking method. With this method, the marks of individual points of the terrain are signed on the map.
Horizontal method.

At present, topographic maps use the method of contour lines in combination with the method of marks, and, as a rule, at least five marks of points are signed on one square decimeter of the map.

Notes

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