Relief shape by relative height. Landform types and their origin



The outline of a section of the earth's surface, including a set of land irregularities (elevations and depressions), as well as the ocean and seabed, is called terrain . The name of the term "relief" is of French origin from "relevo" - I raise.

The terrain is very varied.
The most characteristic landforms are:

Mountain - elevation on the earth's surface in the form of a dome or cone. The mountain has a top, a sole, slopes.
The slopes are gentle and steep. If the slope immediately turns from smooth to steep, it is called a cliff. A very steep cliff is called a cliff.

Basin - a recess on the earth's surface, closed on all sides. Figuratively, one can imagine the hollow as an element of the relief of the earth's surface, opposite to the mountain.
In the basin, slopes (or sides), as well as the bottom, are distinguished.

dell - a hollow of a zholoboobrazny form. In the hollow, also, slopes and bottom are distinguished. The line drawn along the deepest part of the hollow is called catchment line .
The narrow valley is called ravine (in the mountains - gorge ).

Ridge - the relief form, opposite to the hollow, represents an elevated part of the relief, usually elongated, having side slopes.
The upper part of the ridge, drawn along its length, is called watershed line .



Saddle - lowered terrain between two adjacent ridges. Usually a saddle is the beginning of two hollows, spreading in opposite directions from it.
In mountainous areas, saddles are usually crossed by passes - communication routes between mountain ranges, along which roads and trails are laid.

Plain - low-lying terrain with flat terrain. If the height of the plain above sea level does not exceed 200 m, it is called lowlands . A plain located at an altitude of more than 200 m above sea level is called plateau .

To solve many problems of engineering construction, military affairs, and others, it is necessary to have a reliable idea of ​​the relief of a given area. Projecting points on the earth's surface onto a horizontal plane makes it possible to study the distance between objects on this surface with a certain degree of error, but does not give an idea of ​​its relief.
In order for a topographic map or plan to meet the requirements of practical tasks, it is necessary to put on them the designation of irregularities in the displayed area, i.e. relief. To solve this problem, various leveling methods are involved, the results of which are then applied to the graphic image of the site.

Over the long history of the development of cartography, a variety of methods have been used to depict the terrain on flat maps and plans. The most widely used are three methods of drawing relief on a map - strokes, hillshade and horizontal lines. The method of drawing a relief on a plane using strokes has not stood the test of time, and is not currently used, therefore, the methods of horizontal lines and hillshade are usually used to depict the relief on topographic maps and plans.
You can learn more about how terrain elements are depicted on maps in the next article.



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:

1. promising way.
2. 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.
3. Shading method.
4. Marking method. With this method, the marks of individual points of the terrain are signed on the map.
5. 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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s; well. [lat. fōrma appearance, shape, appearance] 1. External outlines, external appearance of an object. The earth is spherical. square f. Curved object. Clouds change their forms. Vessels of various shapes. Water poured into a vessel takes the shape of a vessel. encyclopedic Dictionary

the form- s; well. (lat. fōrma appearance, appearance, appearance) see also. for the form, throughout the form, in the form, mold, formal, uniform ... Dictionary of many expressions

Studying geography and topography, we are faced with such a concept as terrain. What is this term and what is it used for? In this article, we will deal with the meaning of this word, find out what types there are, and much more.

The concept of relief

So what does this term mean? The relief is a set of irregularities on the surface of our planet, which are composed of elementary forms. There is even a separate science that studies its origin, development history, dynamics and internal structure. It's called geomorphology. The relief consists of separate forms, that is, natural natural bodies, representing its individual parts and having their own dimensions.

Variety of forms

According to the morphological principle of classification, these natural bodies can be both positive and negative. The first of them rise above the horizon line, representing an uplift of the surface. An example is a hillock, a hill, a plateau, a mountain, and so on. The latter, respectively, form a decrease relative to the horizon line. These can be valleys, beams, depressions, ravines, etc. As mentioned above, the relief form is composed of individual elements: surfaces (faces), points, lines (ribs), corners. According to the degree of complexity, complex and simple are distinguished. Simple forms include hillocks, hollows, hollows, etc. They are separate morphological elements, the combination of which forms a form. An example is a hillock. It is divided into such parts: sole, slope, top. A complex form consists of a number of simple ones. For example, the valley. It includes the channel, floodplain, slopes and so on.

According to the degree of slope, sub-horizontal surfaces (less than 20 degrees), inclined and slopes (more than 20 degrees) are distinguished. They can have a different shape - straight, convex, concave or stepped. According to the degree of strike, they are usually divided into closed and open.

Relief types

The combination of elementary forms that have a similar origin and extend over a certain space determines the type of relief. In large areas of our planet, it is possible to unite several separate species on the basis of a similar origin or difference. In such cases, it is customary to speak of groups of relief types. When the association is made on the basis of their formation, then one speaks of the genetic types of elementary forms. The most common types of land relief are flat and mountainous. In terms of height, the former are usually divided into depressions, uplands, lowlands, plateaus and plateaus. Among the latter, medium and low are distinguished.

flat relief

This is an area that is characterized by insignificant (up to 200 meters) relative elevations, as well as a relatively small steepness of slopes (up to 5 degrees). The absolute heights here are small (only up to 500 meters). These areas (land, the bottom of the seas and oceans), depending on the absolute height, are low (up to 200 meters), elevated (200-500 meters), upland or high (over 500 meters). The relief of the plains depends primarily on the degree of ruggedness and soil and vegetation cover. It can be loamy, clayey, peaty, sandy loamy soils. They can be cut by riverbeds, gullies and ravines.

hilly terrain

Having a wavy character, forming irregularities with absolute heights up to 500 meters, relative elevations up to 200 meters and a steepness of not more than 5 degrees. The hills are often made of hard rocks, and the slopes and peaks are covered with a thick layer of loose rock. The lowlands between them are flat, wide or closed basins.

uplands

Mountain relief is a terrain that represents the surface of the planet, significantly elevated relative to the surrounding territory. It is characterized by absolute heights of 500 meters. Such a territory is distinguished by a diverse and complex relief, as well as specific natural and weather conditions. The main forms are mountain ranges with characteristic steep slopes, which often turn into cliffs and rocks, as well as gorges and hollows located between the ranges. The mountainous areas of the earth's surface are significantly elevated above the level of the ocean, while they have a common base that rises above the adjacent plains. They consist of many negative and positive landforms. According to the level of height, they are usually divided into low mountains (up to 800 meters), middle mountains (800-2000 meters) and high mountains (from 2000 meters).

relief formation

The age of elementary forms of the earth's surface can be relative and absolute. The first sets the formation of relief relative to some other surface (earlier or later). The second is determined by the relief is formed due to the constant interaction of exogenous and endogenous forces. So, endogenous processes are responsible for the formation of the main features of elementary forms, and exogenous, on the contrary, tend to equalize them. In relief formation, the main sources are the energy of the Earth and the Sun, and one should not forget about the influence of space. The formation of the earth's surface occurs under the influence of gravity. The main source of endogenous processes can be called the thermal energy of the planet, which is associated with radioactive decay occurring in its mantle. Thus, under the influence of these forces, the continental and oceanic crust was formed. Endogenous processes cause the formation of faults, folds, the movement of the lithosphere, volcanism and earthquakes.

Geological observations

Geomorphologists study the shape of the surface of our planet. Their main task is to study the geological structure and terrain of specific countries, continents, planets. When compiling the characteristics of a particular area, the observer is obliged to determine what caused the shape of the surface in front of him, to understand its origin. Of course, it will be difficult for a young geographer to understand these issues on his own, so it is better to turn to books or a teacher for help. Compiling a description of the relief, a group of geomorphologists must cross the study area. If you want to make a map only along the route of movement, then you should maximize the observation band. And in the process of research, periodically move away from the main path to the sides. This is especially important for poorly visible areas, where forests or hills obstruct the view.

Mapping

When recording information of a general nature (hilly, mountainous, rugged, etc.), it is also necessary to map and describe separately each relief element - a steep slope, ravine, ledge, river valley, etc. Determine the dimensions - depth, width, height, angles of inclination - often, as they say, by eye. Due to the fact that the relief depends on the geological structure of the area, when making observations, it is necessary to describe the geological structure, as well as the composition of the rocks that make up the studied surfaces, and not just their appearance. It is necessary to note in detail karst funnels, landslides, caves, etc. In addition to the description, schematic sketches of the study area should also be carried out.

According to this principle, you can explore the area near which your home is located, or you can describe the relief of the continents. The methodology is the same, only the scales are different, and it will take much more time to study the continent in detail. For example, in order to describe, you will need to create many research groups, and even then it will take more than one year. After all, the mentioned mainland is characterized by an abundance of mountains stretching along the entire continent, Amazonian virgin forests, Argentine pampas, etc., which creates additional difficulties.

Note to the young geomorphologist

When compiling a relief map of the area, it is recommended to ask local residents where you can observe the places where rock layers and groundwater come out. These data should be entered on the map of the area and described in detail and sketched. On the plains, rock is most often exposed in places where rivers or ravines have cut through the surface and formed coastal cliffs. Also, these layers can be observed in quarries or where a highway or railway passes through a cut-out recess. The young geologist will have to consider and describe each layer of the rock, it is necessary to start from the bottom. Using a tape measure, you can make the necessary measurements, which should also be entered in the field book. The description should indicate the dimensions and characteristics of each layer, their serial number and exact location.

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Lesson questions:

1. Types and forms of terrain. The essence of the image of the relief on the maps by contour lines. Types of horizontals. Image by contour lines of typical landforms.

1.1 Types and forms of terrain.
In military affairs terrain understand the area of ​​​​the earth's surface on which to conduct hostilities. The unevenness of the earth's surface is called terrain, and all objects located on it, created by nature or human labor (rivers, settlements, roads, etc.) - local items.
The relief and local objects are the main topographical elements of the terrain that affect the organization and conduct of combat, the use of military equipment in combat, the conditions for observation, firing, orientation, camouflage and maneuverability, i.e., determining its tactical properties.
A topographic map is an accurate display of all the most tactically important elements of the terrain, plotted in a mutually exact location relative to each other. It makes it possible to explore any territory in a relatively short time. Preliminary study of the terrain and decision-making for the performance of a particular combat mission by a subunit (unit, formation) is usually carried out on a map, and then refined on the ground.
The terrain, influencing combat operations, in one case can contribute to the success of the troops, and in the other have a negative effect. Combat practice convincingly shows that one and the same terrain can give more advantages to those who study it better and use it more skillfully.
According to the nature of the relief, the area is divided into flat, hilly and mountainous.
flat terrain characterized by small (up to 25 m) relative elevations and a relatively small (up to 2 °) steepness of slopes. Absolute heights are usually small (up to 300 m) (Fig. 1).

The tactical properties of flat terrain depend mainly on the soil and vegetation cover and on the degree of ruggedness. Clayey, loamy, sandy loamy, peaty soils allow the unhindered movement of military equipment in dry weather and significantly impede movement during the rainy season, spring and autumn thaws. It can be indented by riverbeds, ravines and gullies, have many lakes and marshes, which significantly limit the ability to maneuver troops and reduce the rate of advance (Fig. 2).
Flat terrain is usually more favorable for the organization and conduct of an offensive and less favorable for defense.

hilly area characterized by a wavy nature of the earth's surface, forming irregularities (hills) with absolute heights up to 500 m, relative elevations of 25 - 200 m and a prevailing steepness of 2-3 ° (Fig. 3, 4). The hills are usually composed of hard rocks, their tops and slopes are covered with a thick layer of loose rocks. The depressions between the hills are wide, flat or closed basins.

Hilly terrain provides for the movement and deployment of troops hidden from enemy ground observation, makes it easier to choose places for firing positions of missile troops and artillery, and provides good conditions for concentrating troops and military equipment. In general, it is favorable both for the offensive and for defense.
Mountain landscape represents areas of the earth's surface that are significantly elevated above the surrounding area (having absolute heights of 500 m or more) (Fig. 5). It is distinguished by a complex and varied relief, specific natural conditions. The main landforms are mountains and mountain ranges with steep slopes, often turning into rocks and rocky cliffs, as well as hollows and gorges located between mountain ranges. The mountainous area is characterized by a sharp rugged terrain, the presence of hard-to-reach areas, a sparse network of roads, a limited number of settlements, a rapid flow of rivers with sharp fluctuations in water levels, a variety of climatic conditions, and a predominance of rocky soils.
Combat operations in mountainous areas are considered as operations in special conditions. Troops often have to use mountain passes; observation and firing, orientation and target designation are difficult, at the same time it contributes to the secrecy of the location and movement of troops, facilitates the setting up of ambushes and engineering barriers, and the organization of camouflage.

1.2 The essence of the image of the relief on maps by contour lines.
The relief is the most important element of the terrain, which determines its tactical properties.
The image of the relief on topographic maps gives a complete and sufficiently detailed idea of ​​the irregularities of the earth's surface, the shape and relative position, elevations and absolute heights of terrain points, the prevailing steepness and length of slopes.

1.3 Types of contour lines.
Horizontal- a closed curved line on the map, which corresponds to a contour on the ground, all points of which are located at the same height above sea level.
There are the following horizontal lines:

• main(solid) - relief section corresponding to the height;
• thickened - every fifth main horizontal; stands out for ease of reading the relief;
• additional horizontals(semi-horizontals) - are drawn by a broken line at the height of the relief section equal to half of the main one;
• auxiliary - are depicted as short dashed thin lines, at an arbitrary height.

Distance between two adjacent main contour lines in height are called the height of the relief section. The height of the relief section is signed on each sheet of the map under its scale. For example: "Solid contours are drawn through 10 meters."
To facilitate the calculation of contour lines when determining the heights of points on the map, all solid contour lines corresponding to the fifth multiple of the height of the section are drawn thickened and a number indicating the height above sea level is put on it.
In order to quickly determine the nature of surface irregularities on maps when reading a map, special slope direction indicators are used - berghashes- in the form of short dashes placed on the horizontals (perpendicular to them) in the direction of the slopes. They are placed on the bends of contour lines in the most characteristic places, mainly at the tops of saddles or at the bottom of basins.
Additional contours(semi-horizontals) are used to display the characteristic forms and details of the relief (bends of slopes, peaks, saddles, etc.), if they are not expressed by the main horizontals. In addition, they are used to depict flat areas, when the laying between the main contours is very large (more than 3 - 4 cm on the map).
Auxiliary horizontals used to depict individual details of the relief (saucers in the steppe regions, depressions, individual hillocks on flat terrain), which are not transmitted by the main or additional horizontals.

1.4 Depiction by contour lines of typical landforms.
The relief on topographic maps is depicted by curved closed lines connecting points of the terrain that have the same height above the level surface, taken as the origin of the heights. Such lines are called horizontal lines. The image of the relief with contour lines is supplemented by labels of absolute heights, characteristic points of the terrain, some contour lines, as well as numerical characteristics of relief details - height, depth or width (Fig. 7).

Some typical forms of terrain on the maps are displayed not only by the main, but also by additional and auxiliary contour lines (Fig. 8).

Rice. 8. Image of typical landforms

2. Determination on the map of absolute heights and relative elevations of terrain points, ascents and descents, steepness of slopes.

2.1. Determination on the map of absolute heights and relative elevations of terrain points

2.2. Definition on the map of ascents and descents on the route.

Rice. ten. Definition on the map of ascents and descents on the route of movement (route profile). Rice. eleven. Determination on the map of the steepness of the slopes

Profile- a drawing depicting a section of the terrain with a vertical plane. For greater expressiveness of the terrain, the vertical scale of the profile is taken 10 or more times larger than the horizontal one. In this regard, the profile, transmitting the mutual excess of points, distorts (increases) the steepness of the slopes. To build a profile, you need(Fig. 10) : draw a profile line (travel route) on the map, attach a sheet of graphed (millimetric) paper to it, transfer to its edge with short lines the places of contour lines, the inflection points of the slopes and local objects that the profile line cuts, and sign their heights; sign on a sheet of graphed paper at the horizontal lines the heights corresponding to the heights of the contour lines on the map, conventionally taking the gaps between these lines as the height of the section (set the vertical scale); from all dashes indicating the intersections of the profile line with elevation marks of contour lines, inflection points of slopes and local objects, lower the perpendiculars until they intersect with parallel lines corresponding to the marks and mark the resulting intersection points; connect the intersection points of a smooth curve, which will depict the terrain profile (ascents and descents on the route of movement).

2.3. Determination on the map of the steepness of the slopes.
The steepness of the slope on the map is determined by the location - the distance between two adjacent main or thickened horizontals; the smaller the laying, the steeper the slope \.
To determine the steepness of the slope, it is necessary to measure the distance between the horizontals with a compass, find the corresponding segment on the laying chart and read the number of degrees (Fig. 11).
On steep slopes, this distance is measured between thickened contours and the steepness of the slope is determined from the graph on the right.

3. Conventional signs of relief elements that are not expressed by contour lines.

	Ice cliffs (barriers) and outcrops of fossil ice (8 - height of the cliff in meters)
	Sod ledges (edges) that are not expressed by horizontal lines
	Shafts coastal, historical, etc., not expressed by contour lines (3 - height in meters)
	1) Dry channels in one line (less than 5 m wide); 2) Dry channels in two lines with a width of 5 to 15 m (0.5 mm on the map scale); 3) Dry channels more than 15 m wide (from 0.5 to 1.5 mm on a map scale); 4) Dry channels with a width of more than 1.5 mm on a map scale and basins of dry lakes
	Height marks
	Command Height Marks
	Landmark elevations
	Main passes, marks of their heights and duration
	Passes, marks of their heights and duration
	Karst and thermokarst sinkholes not expressed on the map scale
	Pits that are not expressed on the scale of the map
	Pits expressed in map scale
	Rocks-outliers that have a landmark value (10-height in meters)
	Rocks-outliers that do not have a landmark value
	Dikes and other narrow, steeply walled hard rock ridges (5 - height of the ridge in meters)
	Mud volcano craters
	Volcanic craters not expressed on the map scale
	Mounds and mounds that are not expressed on the scale of the map
	Mounds and mounds, expressed on the scale of the map (5 - height in meters)
	Clusters of stones
	Separately lying stones (3 - height in meters)
	Entrances to caves and grottoes

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Fundamentals of external and internal ballistics. Hand grenades. Grenade launchers and rocket-propelled grenades.

§ 11. IMAGE OF RELIEF ON MAPS

A clear and complete perception of the image of the terrain on the map is based primarily on the ability to freely and meaningfully read the image of the earth's surface relief on it:

understand the general nature (type) and structural features of the relief and its individual objects; determine landforms - their configuration, relative size and relative position, as well as absolute heights and mutual elevations of any points in the terrain.

1. Types and elementary landforms

The relief is a set of irregularities of the earth's surface, composed of various elementary forms of various orders.

There are large, structural landforms that form the surface of relatively large geographic regions (mountains, plains, highlands), and elementary forms of irregularities that are less significant in size and make up the surface of these relief objects.

Combinations of homogeneous forms, similar in appearance, structure and size and regularly repeated in a certain territory, form various types and varieties of relief.

According to the elevation above sea level and the degree of dissection of the earth's surface, two main types of relief are distinguished - mountainous and flat. Their classification by height above sea level is indicated in Table. eight.

Table 8

mountainous terrain	Height above sea ​​level, m	flat relief	Height above sea level, m
Low mountains (low mountains) Medium mountains (middle mountains) High mountains (highlands)	500-1000 1000-2000 Over 2000	lowlands Elevated plains (uplands) Plateau	Below 200 200-500 Over 500

The mountain relief is composed mainly of linearly elongated mountain ranges and ridges with their spurs stretching for long distances, separated by longitudinal valleys and other intermountain depressions. In places where they intersect, mountain knots rise, which, like the places where spurs branch off from the main ridge, are usually distinguished by their height and the greatest inaccessibility. The depth of dismemberment reaches: in low mountains - up to 500 m, in middle ones - up to 1000 m, in high ones - more than 1000 m.

The flat relief (plains) is characterized by surface forms with small (within 200 m) elevation fluctuations. The higher above sea level, the more the surface can be dissected.

According to the general nature of the surface, horizontal, inclined, convex and concave plains are distinguished.

The hilly relief is one of the varieties of the flat relief. According to the shape and structure of irregularities, flat-plain, wavy, stepped, ravine-beam and other varieties of flat relief are also distinguished.

The whole variety of irregularities that make up the relief of the earth's surface can basically be reduced to the following five elementary forms:

1) Mountain - a significant dome-shaped or conical elevation with a more or less pronounced base - the sole. A small round or oval hill with gentle (less than 30 °) slopes and with a relative height of not more than 200 m is called a hill, and an artificial hill is called a mound.

2) Hollow - a closed bowl-shaped depression, usually with gentle slopes. In some basins, the bottom is swampy or occupied by a lake.

3) Ridge - a linearly elongated elevation, gradually lowering towards one or both of its ends. The line connecting the opposite slopes of the ridge is called the watershed line, or watershed. It is often also called topographic (geographical) crest, or just a comb.

A mountain range is a chain of mountains extending in one direction. In longitudinal section, the crest of the mountain range is a wavy line. Its protruding parts form the tops. In the planned outline, the ridge usually has a very winding and branching appearance, which is given to it by mountain spurs extending to the sides and their smaller branches.

Elongated elevations with very gentle slopes, imperceptibly turning into a plain, are called ridges.

4) Hollow - an elongated recess, falling in one direction; has slopes with a clearly defined upper inflection - the edge. The line along the bottom, to which the slopes of the hollow are directed, is called the weir, or thalweg; sometimes it is the bed of a stream. Hollows are usually well turfed, often overgrown with shrubs or forests; the bottom is sometimes swampy.

Large and wide hollows with gentle slopes and a slightly sloping bottom are called valleys. In the highlands there are narrow and deep hollows with almost sheer, steep slopes; they are called gorges.

The varieties of hollows also include ravines and beams. ravines- these are large deep gullies with steep, unsoddy slopes, formed by temporary drains. Their length can reach 5 - 10 km, depth - 30 m, width - 50 m or more. Ravines are widespread and occur in a wide variety of conditions - on flat and hilly terrain, on the slopes of mountains and valleys. They are formed and increase from year to year under the influence of melt and rain water in loose and easily eroded soils (loess, clay, loam). Over time, the ravine, having reached the water-resistant layer, ceases to grow in depth, its slopes flatten out, overgrown with grass; the ravine turns into vb a l to y.

In the foothills and on elevated rocky plains, sometimes there are narrow crevices deeply cut by rivers with almost sheer or stepped cheeks - these are canyons. Their depth can reach several tens and sometimes hundreds of meters. The bottom of the canyon is usually completely occupied by the riverbed.

5) saddle - a depression on the crest of a ridge between two adjacent peaks; to it from two opposite directions, transverse to the ridge, the upper reaches of the hollow approach. In the mountains, roads and paths through the ridges pass through saddles, which are called passes.

2. The essence of the image of the relief by contour lines

On topographic maps, the relief is depicted by contour lines, i.e., curved closed lines, each of which is an image on the map of a horizontal contour of unevenness, all points of which on the ground are located at the same height above sea level.

In order to better understand the essence of the depiction of the relief by contour lines, let us imagine an island in the form of a mountain gradually flooded with water. Let us assume that the water level successively stops at equal intervals in height, equal to h meters (Fig. 34).

To each water level, starting from the initial (line AB), will obviously fit its own coastline (CD,KL,MN ,RS) in the form of a closed curve, all points of which have the same height.

These lines can also be considered as traces of the section of uneven terrain by level surfaces parallel to the level surface of the sea, from which the heights are calculated. From this distance h in height between adjacent secant surfaces is called the height of the section.

If all these lines of equal heights are projected onto the surface of the earth's ellipsoid and depicted on a map on a given scale, then we will get an image of a mountain on it in plan in the form of a system of closed curved lines ab,cd,kl , m and rs . These will be horizontal.

From the consideration of the nature of contour lines, the following conclusion can be drawn:

a) each contour on the map is a horizontal projection of a line of equal heights on the ground, depicting the planned outline of the unevenness of the earth's surface. Thus, according to the pattern and the mutual position of the horizontals, one can perceive the forms, the mutual position and the relationship of irregularities;

b) since the contour lines on the map are drawn at regular intervals in height, then by the number of contour lines on the slopes it is possible to determine the height of the slopes and the mutual excess of points on the earth's surface: the more contour lines on the slope, the higher it is;

c) the laying of contour lines, i.e., the distances in plan between adjacent contour lines, depend on the steepness of the slope: the steeper the slope, the less the laying. Therefore, by the magnitude of the foundation, one can judge the steepness of the slope.

3. Types of contour lines

The height of the relief section on the map depends on the scale of the map and the nature of the relief. Usually it is equal to 0.02 of the map scale value (for example, on maps of scales 1:50000 and 1:100000, the normal height of the section is 10 and 20 m, respectively). On the maps of high-mountain regions, in order for the image of the relief not to be obscured due to excessive density of horizontal lines and to be better read, the height of the section is taken twice as normal (on a map of a scale of 1:25000 - 10 m, 1:50000 - 20 m, 1: 100000 - 40 m, 1:200000 - 80 m). On maps of flat-plain regions at scales of 1:25,000 and 1:200,000, the height of the section is taken to be half the normal height, i.e., 2.5 and 20 m, respectively.

The contours on the map, corresponding to the height of the section set for it, are drawn by solid lines and are called the main, or solid, contour lines (Fig. 35).

It often happens that important details of the relief are not expressed on the map by the main horizontal lines. In these cases, in addition to the main horizontals, half (semi-horizontals) are used, which are drawn on the map through half the main height of the section. Unlike the main half horizontals, they are drawn with broken lines.

In some places, where the necessary details of the relief are not expressed by the main and half horizontals, additional auxiliary horizontals are drawn between them - approximately a quarter of the height of the section. They are also drawn with broken lines, but with shorter links.

To facilitate the calculation of contour lines when determining the heights of points on the map, all solid contour lines corresponding to five times the height of the section are drawn thickened (thickened horizontal).

The main height of the section is indicated on each sheet of the map - under the southern side of its frame. For example, the inscription "Solid contour lines are drawn through 10 m" means that on this sheet all the horizontal lines shown by solid lines are a multiple of 10 m, and thickened ones are a multiple of 50 m.

4. Depiction by contour lines of elementary landforms

On fig. 36 shows the elementary landforms separately in horizontal lines. The figure shows that a small mountain (hill) and a hollow look in general the same - in the form of a system of closed contour lines encircling each other. The images of the ridge and the hollow are similar to each other. They can only be distinguished by the direction of the slopes.

Pointers of the direction of the slopes, or berghstrichami, are short dashes placed on the horizontals (perpendicular to them) in the direction of the slopes. They are placed on the curves of contours in the most characteristic places, mainly at the peaks, saddles or at the bottom of the basins, as well as on gentle slopes - in places that are difficult to read.

Altitude marks on the maps also help determine the directions of the slopes:

Horizontal marks, i.e. digital signatures on some contour lines, indicating in meters

their height above sea level. The top of these numbers is always facing upward slope;

Elevation marks of individual, most characteristic points of the terrain - the tops of mountains and hills, the highest points of watersheds, the lowest points of valleys and ravines, the levels (edges) of water in rivers and others

reservoirs, etc.

On maps at a scale of 1:100,000 and larger, the elevations of points above sea level are signed with an accuracy of 0.1 m, and on maps of 1:200,000 and smaller - to whole meters. This must be kept in mind in order not to confuse points when indicating and identifying their marks on maps of different scales.

5. Features of the image of flat and mountainous relief by contour lines (see appendicesVI-1,VI-2 andVII-2).

Irregularities with large, clearly defined and smooth forms are most clearly represented by horizontal lines. The image of a flat-plain relief turns out to be less expressive, since the horizontals here pass at a considerable distance from one another and do not express many of the details that lie between the horizontals of the main section. Therefore, along with the main (solid) contour lines, semi-horizontal lines are widely used on maps of flat regions. This improves the readability and detail of flat relief images. When studying such a relief and determining its numerical characteristics from the map, one must be especially careful not to confuse the half and auxiliary horizontals with the main ones.

When studying a mountainous and strongly rugged relief on a map, on the contrary, one has to deal with a very dense arrangement of contour lines. With a large steepness of the slopes, the laying in some places is so small that it is not possible to draw all the horizontals here separately.

Therefore, when depicting slopes on maps, the steepness of which is greater than the limiting one, the horizontals are drawn together one with the other or by a dotted line, leaving only two or three intermediate horizontals instead of four between the thickened horizontals (see Appendix VII-2). In such places, when determining the heights of points or the steepness of slopes on a map, thickened contour lines should be used.

6. Conventional signs of relief elements that are not expressed by horizontal lines

Objects and details of the relief that cannot be depicted by contour lines are shown on the maps with special conventional symbols (see Appendix VII-2).

Such objects include cliffs, rocks, scree, ravines, gullies, ramparts, road embankments and cuts, mounds, pits, sinkholes. The numbers accompanying the symbols of these objects indicate their relative heights (depths) in meters.

Conventional signs of natural relief formations and the signatures of characteristics related to them, as well as horizontal lines, are printed in brown ink, and artificial ones (embankments, excavations, barrows, etc.) are printed in black.

Special conventional symbols in black are depicted:

rocks - remains, large separately lying stones and clusters of stones, which are landmarks, with an indication of their relative heights; caves, grottoes and underground workings with their numerical characteristics (in the numerator - the average diameter of the entrance, in the denominator - the length or depth in meters); tunnels indicating their height and width in the numerator, and their length in the denominator. On roads and trails crossing mountain ranges, passes are marked with an indication of their height above sea level and the time of action.

Annex VII-2 (bottom figure) shows a section of high-altitude relief with its peculiar forms. Here, in combination with contour lines, the conventional signs of the most typical objects of such a relief are shown.

The relief of eternal snows (firn fields) and glaciers is also depicted by horizontal lines, but in blue. The same color shows all the symbols related to it (ice cliffs, ice cracks, icing) and numerical marks of heights and contours.

7. Features of the relief image on maps of scales 1: 500,000 and 1: 1,000,000

The relief on small-scale topographic maps, as well as on maps of larger scales, is depicted by contour lines and conventional signs, but more generally. They display only the general nature of the relief - its structure, main forms, the degree of its vertical and horizontal dissection.

The height of the main section when depicting flat areas on both maps is set to 50 m, and mountainous - 100 m. On a map of a scale of 1: 1000000, in addition, a section height of 200 m is used to depict areas located above 1000 m above sea level.

Relief objects that are not expressed as contour lines are shown only those that are necessary to characterize the terrain or are important landmarks. They are marked mainly by the same symbols as on other maps, but smaller.

The main feature is the depiction of mountainous terrain. For greater clarity, its image with contour lines is supplemented by the so-called hillshade and layer-by-layer coloring by height steps (see appendices V-5 and V-6).

Hillshade, i.e. shading the slopes of the most important forms of mountain relief, makes the image more expressive and plastic, allowing you to visually feel its three-dimensional forms. Shading is done with gray-brown paint according to the principle - the more significant, higher and steeper the slope, the stronger the tone of the hillshade.

Thanks to hillshading, the main mountain ranges and massifs, their most important spurs and peaks, passes, ledges of highlands, deep valleys and canyons are well distinguished. The direction and comparative steepness of the slopes, the shape of the ridges (sharp, rounded, etc.) and the difference in height of the main mountain ranges are clearly perceived.

Layered coloring by height steps clearly displays the high-altitude characteristics of the mountainous relief and enhances the plastic effect of its image. It is performed with orange paint of various tones according to the principle - the higher, the darker. In this case, the image of the relief is, as it were, divided into separate high-altitude layers (steps), according to the color tone of which their absolute heights and mutual excesses are easily distinguished. The color tone of the layers intensifies after 400, 600 or 1000 m, depending on their absolute heights. The scale of elevation steps adopted on the map is indicated on each sheet, under the southern side of its frame.