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
Figure No. 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 in 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 oceans, lying between the coast and the continental slope. By the way, this former coastal plain in the topography of the ocean floor is expressed 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 will be 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. The continental shelf is traditionally narrow on mountainous coasts, while on flat coasts it is wide. The continental shelf reaches its greatest width off the coast 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.
Figure No. 2. Relief forms of the bottom of the World Ocean
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°) Average width 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. It is worth noting that 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 will be underwater terraces. These are underwater terraces Sea of Japan, located at a depth of 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. Do not forget that the most important elements of its relief will be abyssal plains, ocean basins, deep-sea ridges, mid-ocean ridges, hills and underwater plateaus.
In the central parts of the oceans are located mid-ocean ridges, rising to a height of 1-2 km and forming a continuous ring of uplifts in the Southern Hemisphere at 40-60° S. w. Three ridges extending northward 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. It is important to note that some of them are flat, others are undulating with a height range of up to 1000 m. It is important to note that one plain is separated from another by ridges.
Some of the single mountains located on the abyssal plains protrude above the surface of the water in the form of islands. It is important to know that 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 are formed - 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. It's worth noting that they are located where the oceanic crust subducts beneath the 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 will be 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 will be Mount Chomolungma - 8848 m.
Considering the dependence on height, mountains are low, medium, high and highest (Fig. 3)
Figure No. 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 mentioned mountains, on globe there are many others. You can get acquainted with them from the atlas maps.
According to the method of formation they distinguish the following types mountains:
- folded - formed as a result of the crushing of a thick layer of sedimentary rocks into folds (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 raising hard blocks to a great height earth's crust; characteristic of ancient platforms: internal forces The earth splits the rigid foundation of the platforms into separate blocks and raises them to a considerable height; as a rule, ancient or revived) (Fig. 5);
- folded-block - ϶ᴛᴏ old folded mountains, which were largely destroyed, and then, in new periods of mountain building, their individual blocks were again raised to great heights (Fig. 6)
Figure No. 4. Formation of folded mountains
Figure No. 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.
Figure No. 6. Formation of folded-block renewed mountains
Note that tectonic mountains — ϶ᴛᴏ mountains, which 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 -϶ᴛᴏ volcanic cones, lava flows and tuff covers distributed over large territory 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. Note that thermal 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.
Taking into account the dependence on the areas occupied by mountains, their structure and age, mountain belts are distinguished, mountain systems, mountainous countries, mountain ranges, mountain ranges and elevations of a smaller rank.
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 mountainous terrain, representing 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.
Figure No. 7. Formation of plains
Taking into account the dependence on height, among the plains the land is distinguished:
- 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. Taking into account the dependence on the nature of the mesorelief, which complicates 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 will be the following:
Land occupies exclusively 29% of the Earth's surface, which is 149 million km 2.
It is worth noting that 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 exclusively for about 1.5% of the ocean's area.
Landforms are characterized by many indicators - origin, relationship to the earth's surface, isolation and size.
The origin of relief forms is determined mainly by two factors - nature and man-made human activity. Thus, all forms of land relief are divided into natural and anthropogenic.
Natural landforms are born as a result of three processes:
- 1) movements of the earth’s crust;
- 2) destructive erosion and abrasive activity of the hydrosphere (as well as aeolian factors);
- 3) accumulation (accumulation) of precipitation on the surface of the earth.
These processes create the following landforms:
- 1) tectonic - mountain ranges, plains, ocean basins; these forms are quite stable and they are disrupted mainly by tectonic processes and seismic phenomena;
- 2) erosive - formed as a result of erosive activity surface waters(ravines, river valleys); these landforms are unstable and change over time;
- 3) accumulative - created as a result of the accumulation of precipitation; these are forms washed by water (river sediments, river deltas, debris flow cones, etc.) and blown by the wind (desert dunes, dunes of sea coasts, etc.); forms are very unstable, changing quite quickly over time.
Anthropogenic landforms. On modern stage In the history of the Earth, the relief of its surface began to change intensively due to man-made human activity. Landforms appear that nature does not create. Anthropogenic forms are formed as a result of the work of mining and industrial enterprises, engineering and construction activities, military operations, and during the development of land for agriculture.
Anthropogenic landforms include planned land under agricultural and construction work ah, heaps of waste rock during mine development, earth dumps during quarrying, excavations and embankments during road construction and etc.
Anthropogenic forms can be relatively stable, such as road embankments and cuttings, but in most cases they are temporary. An example is roadside quarries intended for filling embankments. Upon completion of construction work, these landforms cease to exist due to the leveling of the land.
In relation to the surface of the earth, landforms are divided into positive, which rise above the ground, and negative, i.e. depressions.
TO positive forms relief include:
- 1. Highlands- a vast upland consisting of a system of mountain ranges and peaks (for example, the Pamirs).
- 2. mountain ridge- a low mountain range with gentle slopes and a flat top (for example, the Donetsk Ridge).
- 3. mountain range- elongated hill with relative height more than 200 m and with steep slopes.
- 4. Mountain- an isolated hill with steep slopes, more than 200 m high.
- 5. Plateau - mountainous plain, vast in area, with flat peaks.
- 6. Plateau- an elevated plain bounded by well-defined, often steep slopes.
- 7. Ridge- a narrow elongated hill with slopes steeper than 20° and flat tops.
- 8. Uval - an elongated hill of great length, with gentle slopes and flat tops.
- 9. Hill- an isolated dome-shaped or conical hill with gentle slopes and a height of less than 200 m.
- 10. Kurgan - artificially created hill.
- 11. Hillock- an isolated dome-shaped hill with a pronounced bottom lithium with a slope steepness of no more than 25° and flat tops.
- 12. Stem cone- low elevation of land at the mouth of watercourses, such as rivers, ravines, etc.
Negative forms are:
- 1. Basin- reduction of significant depth with steep slopes; a shallow depression with gentle slopes is called a depression.
- 2. Valley- an elongated depression that has a slope in the same direction with slopes of various steepness and shape.
- 3. Beam- an elongated depression of considerable length, with turfed gentle slopes on three sides.
- 4. Ravine- an elongated depression with steep and sometimes sheer slopes.
- 5. Gulch- a small elongated shallow depression with steep, unturfed slopes on three sides.
Landforms based on closedness in space divided into open(ravine, notch) and closed(mountain, embankment).
Based on size, relief forms are usually divided into seven types: smallest, very small, small, medium, large, largest and greatest.
The smallest forms - size in centimeters (sand ripples, furrows in fields, etc.). These forms are not shown on topographic maps.
Very small forms- size from tens of centimeters to 1-2 m (bumps, ruts, small gullies). On large-scale maps they are indicated by symbols.
Small forms sometimes called microrelief. These forms occupy small areas (several square meters and sometimes more) at a height of several meters. These forms are reflected on maps at scales of 1:10,000, 1:5000 and larger.
Medium forms(mesorelief) are divided into positive and negative. Positive forms include hills, mounds, mounds, ridges, ledges, terraces of river valleys, seashores and lakes. In terms of plan, they occupy hundreds, thousands or more square meters. Many of them are long. Negative forms - ravines, beams, karst funnels, hollows.
Mesorelief is clearly depicted on topographic (geomorphological) maps at a scale of 1:50,000 and plays important role when designing roads and airfields.
Large forms(macrorelief) - in plan they occupy tens, hundreds and less often more than square kilometers with a depth division of 200-2000 m. Such relief is reflected on maps of 1:100,000 and 1:1,000,000. Positive forms - mountain ranges, individual mountains, mountain ranges; negative - large valleys, lake depressions such as Lakes Ladoga and Onega. This type of relief makes it possible to evaluate entire territories when planning the placement of construction projects.
Largest forms relief (megarelief) occupy tens and hundreds of square kilometers. These are large hills and basins. The difference in elevations can reach 500-4000 m. Due to their size, such forms can be displayed on maps at a scale of at least 1:10,000,000.
Greatest(planetary) forms - the area is millions of square kilometers, the difference in elevations is 2500-6500 m, the maximum is 20,000 m. Positive forms are continents, and negative forms are oceanic depressions.
The scales of topographic maps are very different and are used in construction depending on the stages of design of objects. In some cases, small-scale maps are needed, and in others, large-scale maps. These can be maps from 1:2000 to 1:1,000,000; large relief forms are displayed as contour lines, and small ones as conventional (standard) signs.
By relief we mean a combination various forms earth's surface. The continent of Eurasia is based on large tectonic structures: folded formations, platforms and shields. They are assigned a leading role in shaping the relief of Russia, which occupies the lion's share of the continent's territory. Highlands and lowlands are adjacent to mountain ranges, but most of the country is occupied by plains.
Features of the Russian landscape
Physical relief map of Russia/Wikipedia
Landscape is usually called an area with the general characteristics of the relief of the earth's surface. Due to its large extent, the country's territory is characterized by frequent changes in landscape. There is a wide variety of landforms, however, most of The territory is flat. The south and east of Russia are represented by mountain complexes. The total length is more than 2 million km. The area is approximately 350 thousand km². Eight main landforms alternate from west to east:
the East European Plain
The territory covers an area of about 4 million km², and is. It stretches from the Baltic Sea to the Black and Caspian Seas and from the Vistula River to the Ural Mountains. The plain differs from other zones in the diversity of its relief. Lowlands alternate with hills. The lowest areas are located off the coast of the Caspian Sea. The elevations reach 500 m.
West Siberian Plain
The territory covers 2.6 million km². Its borders are the Ural Mountains in the west and the Yenisei River in the east. The relief is characterized by uniformity, the maximum height is 200 m. There are many interfluves and river valleys. Part of the land is occupied by swamps.
North Siberian Lowland
The territory extends from the mouth of the Yenisei to the Olenek River, completely covering Taimyr. It lies in the lowered part of the Siberian Platform. Permafrost landforms dominate, and most of the land is swampy. The highest point is 300 m.
Central Siberian Plateau
The territory covers 3.5 million km². The natural boundaries are the Yenisei River in the west and the Lena River in the east. It lies entirely on the Siberian platform. The region is dissected by river valleys. Plateaus give way to rolling hills. The highest point is 1701 m.
South Siberian Mountains
The area of the territory is 1.5 million km². The borders are considered to be the plains of Western Siberia and the Pacific Ocean. The mountain belts were formed due to tectonic uplift. The highest point is Mount Belukha, 4509 m. The landscape is represented by mountain and alpine meadows.
Central Yakut Lowland
The lands extend from the Lena River to the Vilyui River. There are many ponds and swamps on the territory. West Side has a flat character. The average height does not exceed 100 m. The average elevation in the east is 300 m. Depressions and hills are common in the area.
East Siberian Highlands
The area of the territory is 2 million km². This includes part Far East, North-Eastern district of Siberia and East Asia. The relief is mostly represented by mountain ranges. The highest point is Mount Pobeda, 2443 m. From west to east they flow large rivers Yana, Indigirka, Kolyma.
East Siberian Lowland
The territory is located in the northeast of Yakutia. The maximum height is 300 m. The landscape is dominated by permafrost. The area is mostly marshy. As a result of the pushing of glaciers, many mounds were formed.
Geographical location of Russia relative to major landforms
Most of the territories lie on the large Eurasian plate. Kamchatka and the coast Magadan region located on the Sea of Okhotsk plate. Chukotka autonomous region located on the North American Plate. Southern territories Siberia lies within the Amur lithospheric plate.
A platform is a virtually stationary part of the earth's crust. The East European Plain lies on the Russian Platform. The West Siberian is located on the young West Siberian Platform. The Central Siberian Plateau belongs to the Siberian Platform.
The tectonic structure that separates the platforms from each other is called a fold belt. Mountains form within its boundaries. Folding in the history of the formation of the relief of Russia:
- Baikalskaya;
- Caledonian;
- Hercynian;
- Mesozoic;
- Cenozoic.
Each era ends with the formation of new mountain systems.
Mountain systems of Russia
Mountain Elbrus
Altai
The Siberian ranges were formed during the Baikal and Caledonian folding eras. They are located on the border of Russia, China, Mongolia and Kazakhstan. The relief is divided into high-mountain and mid-mountain. The hilly surface occupies a third of all land. The height of the ridges is on average 4000 m. The stone bases have been subject to erosion and weathering. The mid-mountain relief does not exceed 2000 m. The ridges are low, rounded, and in some places they are separated by river valleys. In the foothill plains, low-mountain relief is distinguished; altitudes range from 400 to 800 m. There are a lot of basins in Altai. They occupy entire valleys. Some of them are located at heights, others lie in lowlands, so they became the bottom of lake basins.
Ural Mountains
The Urals are the border between the East European and West Siberian plains. The mountains were formed during the era of the Hercynian folding. The territory is a system of ridges that stretch parallel to each other. The western slopes of the Urals are flatter. The highest point is Mount Narodnaya, 1895 m. The mountain system crosses several. There are many lakes in the mountains, and numerous rivers originate at the foothills.
In the depths of the mountains there are mineral deposits, there are 55 species in total. They mine here Various types ores, gold, coal, platinum. The Urals region is known for oil and gas deposits. The Ural Mountains became especially famous thanks to deposits of precious stones: emeralds, topazes, diamonds, alexandrites.
Caucasus Mountains
The ridges lie between the Black, Azov and Caspian Seas. The mountains were formed during the era of the Hercynian folding. It is customary to divide the territory into the Greater and Lesser Caucasus. The highest point of the feather region is Mount Elbrus, 5642 m. Some mountains retain. The Greater Caucasus stretches from Taman to Baku.
The Lesser Caucasus is allocated a mountain range near the Black Sea. The territory is rich in mineral deposits. Oil and gas have been discovered here, as well as many reserves of hydrocarbons, iron ores, mercury, copper, lead and zinc.
Khibiny
The ranges are located in the Murmansk region, beyond the Arctic Circle. The mountains were formed during the Baikal folding era. The mountain system has an oval shape. The slopes are snow-covered, and river valleys have formed at the foot. The relief was influenced by glaciers. The highest point of the system is Mount Yudychvumchorr, its height is 1200 m. The relief is still being formed. The Khibiny Mountains are famous for apatite, molybdenum, zirconium and titanium. There is a danger of an avalanche. However, the place is popular ski resort. Due to its location above the Arctic Circle, you can come here for skiing all year round.
Large tectonic structures have influenced the variety of relief forms in Russia. On the territory of the country there are lowlands, plateaus, mountains, and hills. The predominant form is plain; to the north there is a general decrease. The highest mountains are located in the south. In the depths of the mountains there is a whole range of minerals.
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Depending on the nature of the relief, the terrain is divided into flat, hilly and mountainous. The terrain is made up of various combinations of land surface shapes, the main ones being hill, basin, ridge, ravine and saddle.
Hill, mountain– a convex, cone-shaped form of relief, rising above the surrounding area (Fig. 3)
Figure 3 - Hill
The highest point of a mountain or hill is called top. From the top there are slopes in all directions; the line of transition of the slopes into the surrounding plain is called sole. A mountain differs from a hill in size and steepness of slopes; at a height above the surrounding area of up to 200 m, a similar form of relief with gentle slopes is called hill, and more than 200 m with steep slopes - mountain. Mountains and hills are depicted as closed horizontal lines with strokes directed from the top to the bottom.
A basin or depression is a relief form opposite to a mountain (hill), representing a bowl-shaped depression of the earth’s surface (Fig. 4).
Figure 4 - Basin or depression
The lowest point of the basin is called bottom. Side surface consists of slopes; the line of their transition to the surrounding area is called edge. The basin, like the mountain, is depicted with closed horizontal lines, but the strokes in this case are directed towards the bottom.
Ridge– an elongated hill gradually descending in one direction (Fig. 5).
Figure 5 - Ridge
A ridge is usually an offshoot of a mountain or hill. The line connecting the highest points of the ridge, from which slopes extend in opposite directions, is called watershed. The ridge is depicted by convex horizontal lines, convexly directed towards the lower terrain.
Hollow– an elongated or gradually descending hill in one direction (Fig. 6).
Figure 6 - Hollow
Two slopes of the valley, merging with each other in its lowest part, form a line spillway or thalweg. The varieties of hollow are: valley– a wide hollow with gentle slopes; ravine- (V mountainous area – gorge) is a narrow ravine with steep exposed slopes. The hollow is depicted by concave horizontal lines, concavity directed towards the lowering of the terrain; steep slopes of the ravine are depicted with special symbols (Fig. 7).
Figure 7 - Ravine
A saddle is a low area of terrain located on a ridge between neighboring peaks (Fig. 8).
Figure 8 - Saddle
Two valleys originate from the saddle and spread in opposite directions. In mountainous areas, saddles serve as communication routes between opposite slopes of the ridge and are called passes. The saddle is represented by horizontal lines facing each other with their bulges.
The top of the mountain, the bottom of the basin, the lowest point of the saddle and the inflection points of the slopes are called characteristic relief points , and the watershed and drainage lines are characteristic relief lines .
All forms of relief are formed from a combination of inclined surfaces - slopes, which are divided into flat, convex, concave And mixed(Fig. 9).
flat slope convex slope concave slope mixed slope
Figure 9 - Shapes of slopes
As can be seen from Figure 9, the horizontal lines depicting an even slope are located at equal distances from each other. With a convex slope, the distances between horizontal lines at the bottom are smaller than at the top. With a concave slope, the horizontal lines at the bottom are spaced at a greater distance from each other than at the tops. Consequently, by the nature of the contour lines on a topographic map or plan, one can determine the shape of the slopes.
Contour properties
The following basic properties follow from the essence of depicting relief with horizontals:
1. All points lying on the same horizontal line have the same height.
2. Contour lines closed within a map or plan indicate a hill or basin.
3. Contour lines on a plan or map must be continuous lines.
4. Horizontal lines cannot intersect or branch. An exception may be the case when horizontal lines represent an overhanging cliff. Therefore, a special symbol has been installed to depict rocks on maps (including overhanging cliffs).
5. The distance between horizontal lines in plan (lay) characterizes the steepness of the slope, i.e. the angle of inclination of the slope to the horizon v.
As follows from Figure 10, b, the angle of inclination v 1 of the terrain line AB, which the mortgage corresponds to Ab, greater than the angle of inclination v 2 lines AC, the foundation of which Ac>Ab, therefore, for a given height of the relief section h The steeper the line, the smaller its depth.
Figure 10 - Slope steepness (section)
The position (Fig. 11), normal to the horizontals and being the shortest, is called laying down the slope. Mortgage Ab = d corresponds to the terrain line AB greatest steepness, called slope line, which is taken as the direction of the slope at a given point A.
Figure 11 - Steepness of the slope (plan)
The ratio of the height of the relief sections to the foundation is called line slope:
Line slopes are expressed as percentages or ppm (thousandths of a unit).
For example: h=1 m, d=40 m. Then i=1m / 40m = 0.025= 25 0 / 00 = 2.5%.
Having determined the slope of the terrain line, it is easy to find the steepness of the slope by this direction from the expression
6. The lines of watersheds and spillways are intersected by horizontal lines at right angles (Fig. 5, 6).
7. Horizontal lines have marks that are multiples of the height of the relief section. For example, at the height of the relief section h=1 m horizontal lines will have marks of 120; 121; 122; 123 m, etc.; at h= 2.5 m - 120; 122.5; 127.5; 130 m, etc.
When reading a map or plan, as well as when drawing them up, you should remember that all horizontal lines, berghstrokes, height signatures and other conventional signs related to the relief are depicted in brown ink (burnt sienna).
3.1.3 Drawing contour lines using point marks
In the process of topographic survey, the planned position of characteristic points of the terrain with their marks is obtained on the tablet. Based on the marks of these points, the terrain is depicted in contour lines. To do this, guided by the scale of the plan or map being drawn up and the nature of the terrain being photographed, the height of the relief section is selected in accordance with the requirements of the instructions. Points lying on the same slope are connected by straight lines. Then, on each line, points are found whose marks are multiples of the height of the relief section; this action is called interpolation of contour lines.
Interpolation of contours can be done “by eye” or graphically. Interpolation “by eye” can be carried out during the shooting process if the performer has the appropriate professional skills. Essence graphic interpolation is as follows.
Let on the line 1 -2 (Fig. 12) , the elevations of points 1 and 2 are equal to, respectively, 48.7 m and 51.2 m, it is required to find the position of points with elevations that are multiples of the selected height of the relief section h= 1 m, i.e. 49, 50 and 51 m.
Figure 12 - Graphic interpolation of contour lines:
a - using graph paper; b, c - using a palette
On a sheet of graph paper, a series of parallel lines are drawn at equal distances (for example, 0.5 or 1.0 cm), which are digitized according to the point marks and the accepted cross-section of the relief.
By attaching a sheet of graph paper to the line 1 -2, demolish points 1 and 2 according to their marks on the graph paper. By connecting the obtained points 1 and 2 with a straight line, we obtain a profile along line 1-2. Mark the intersection points of the 1" - 2" profile line with the digitized graph paper lines (points a, b, c). By projecting these points onto a line 1 -2, obtain the position of the points through which the horizontal lines with marks of 49, 50 and 51 cm should pass.
In practice, instead of graph paper for graphic interpolation, they often use a palette - wax (tracing paper) with a number of parallel lines drawn at equal intervals (for example, every 0.5 cm). The lines are digitized according to the selected height of the relief section and the marks of the plan points between which interpolation is performed. Place the palette, for example, on line 3-4 (Fig. 12) so that point 3 is on the corresponding mark on the palette. Then, pressing the palette at point 3 with a needle, rotate the palette around this point until point 4 is at the corresponding mark on the palette (Fig. 12) . The points where the line intersects 3 - 4 lines of the palette are pinched onto the plan and a corresponding mark is signed at each of the points. All other lines are interpolated in the same way. Then points on the plan with the same marks are connected by smooth curved lines and a relief image is obtained with horizontal lines.
3.1.4 Determine the elevation of point A lying on the horizontal
The elevation of a point lying on a horizontal line is equal to the elevation of this horizontal line. Consequently, the task comes down to determining the horizontal mark on which a given point lies (Figure 3). If the horizontal mark is not signed, the height of the relief section is determined as the quotient of dividing the difference of two signed horizontal lines by the number of intervals
between them.
Figure 13 - Determining the elevation of a point lying on the horizontal
h = (170.0 – 160.0) / 4 = 2.5 m
Then, using the contour lines and berg strokes, the direction of the slope is determined. The elevation of the point is equal to the elevation of the labeled horizontal line plus or minus the height of the section multiplied by the number of intervals.
H A = 160.0 m + 2.5 m = 162.5 m
3.1.5 Determine the elevation of point B lying between the horizontal lines
Through given point(Figure 14) you need to draw an auxiliary line intersecting the horizontal lines at a right angle. Measure the length of this line l mn and the distance from point B to the nearest horizontal line l bn. The elevation of the point is determined if the excess h is added to the horizontal elevation, calculated from the proportion:
h"/h = l M B/ l MN,
whence h" = (h l MV) : l MN,
where h is the height of the horizontal sections;
l MN – length of the drawn auxiliary line;
l BN – distance from a point to the nearest smallest horizontal line;
Figure 14 - Determining the elevation of a point lying between the horizontal lines
l MN = 8 mm; l BN= 7 mm; h = 2.5 m;
h´ = (h l M B)/ l MN = (2.5 7)/15 = 1.16 m;
H B = 177.5 m – 1.16 m = 176.34 m.
These calculations are made taking into account the image scale.
; a set of irregularities on land, the bottom of oceans and seas, varied in outline, size, origin, age and history of development. The relief is composed of positive (mountain ranges, hills, hills, ridges) and negative (depressions, basins, valleys) forms.
Landforms - individual irregularities in the surface of the lithosphere:
— convex - positive relief forms;
- concave - negative forms of relief.
Landforms vary:
- by size: planetary forms, megarelief, macrorelief, mesorelief, microrelief, nanorelief;
— by origin: tectonic, volcanic, water-erosive, karst, aeolian, etc.;
- by age and other characteristics.
Landforms are usually associated with each other and are grouped into relief types, which together make up the Earth's relief.
The main planetary landforms are continental ridges and oceanic trenches.
Mountains are high above the plains and sharply dissected areas of the earth's surface, with significant differences in elevation. The mountains can reach several kilometers in height. The mountains are delimited from the adjacent plains by a clear line at the base of the slope or have foothills. Mountains usually form straight or arc-shaped uplifts.
Depending on the areas occupied by mountains, their structure and age, mountain belts, mountain systems, mountainous countries, mountain ranges and uplifts of a smaller rank are distinguished, separated by intermountain depressions, the combination of which gives different types of mountain division: parallel, radial, cirrus, echelon, branched, trellised, etc.
Mountains form in tectonically active areas. Based on their origin, mountains are divided into tectonic, erosional, and volcanic.
The main elements of mountain relief are peaks, ridges, leveling surfaces, slopes, etc.
Based on their absolute height and appearance, mountains are divided into high mountains (more than 2-3 km), middle mountains (less than 2-3 km) and low mountains (up to 1000 m).
Block mountains are mountains whose relief is formed mainly by the movements of individual blocks of non-plastic earth's crust, broken by faults into sections that form horsts and grabens as a result of movements.
During tectonic movements in those folded areas where plasticity has been lost, rocks crushed into folds are broken by faults, and folded block mountains arise: Tien Shan, Altai, etc.
Fold mountains arise in mobile zones of the earth's crust. Rocks in folded mountains they are crushed into folds of varying sizes and steepness.
Mesas are isolated elevations formed by the dissection of a highly elevated strata plain or plateau. Table mountains have steep slopes and flat tops, armored with erosion-resistant rocks.
Volcanic mountains are individual volcanic cones and ridges formed as a result of the merger of individual (volcanic ridge in the Eastern Carpathians, etc.) or volcanic highlands (Armenian Highlands, etc.). Volcanic mountains can form mountainous countries.
A plain is a vast relief element of the earth's surface, with small slopes and slight fluctuations in height. The appearance of the plain is determined by the density of the river network and the depth of river valleys, as well as interfluves. The surface of a plain can be horizontal, inclined, or concave.
On land, according to absolute height, they are distinguished:
- plains below sea level;
— low-lying plains with heights from 0 to 200 m;
- elevated plains with heights from 200 to 500 m;
- mountainous plains with altitudes above 500 m.
According to the structural principle there are:
— plains of platform areas - areas of quiet tectonic and magmatic activity;
- plains of orogenic (mountainous) regions, characterized by intense activity of the earth's interior.
There are flat, hilly, ridged and other plains.
Based on the total impact of external (exogenous) processes, accumulative and denudation plains are distinguished.
The main forms of the Earth's relief are reflected on the physical map in geographical atlases.
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