Types of relief and their origin
Depending on the extent (size) and predominance of certain forms of relief, types of relief are distinguished : flat, hilly and mountainous terrain.
The forms and types of relief are, as indicated above, the result of geological processes, are composed of certain rocks and are divided by origin depending on the predominant factor - the force that caused their formation.
Forms and types of relief caused by the activity of endogenous forces, i.e. formed due to movements of the earth's crust and lithosphere (vertical or oscillatory, horizontal or mountain-building) and accompanying magmatism and metamorphism, are called tectonic forms . These forms and types include the largest relief forms: macro -, megareliefplanetaryrelief , arising and lying on geological structures of global and largest sizes. Builders erect various structures, mainly on land (continents), within which platforms and folded mountainous areas with smaller structures are distinguished. Therefore, we will consider below the types of relief characteristic of continents. They, like the geological structures or tectonics of the Earth, seem constant over a large period of geological time (thousands and hundreds of thousands of years).
Landforms created by endogenous processes change under the influence of exogenous forces that flow on the Earth's surface under the influence of external energy sources (solar radiation, temperature fluctuations, movement and composition of water and wind, living organisms, including humans). The listed energy sources operate and change constantly; the relief forms they form are not constant and actively change their shape over time. Among the exogenous forms of relief, the most striking are those that arose due to the destructive and creative activity of exogenous processes. Erosion forms (gorges, river valleys, ravines, gullies, funnels) arose as a result of the destructive action of flowing waters (atmospheric, river and underground). They are very dynamic in their outlines and can change noticeably before the eyes of one generation of people. Within their limits, other exogenous processes can develop: landslides, landslides, etc. Accumulative forms of relief arise when the strength of the exogenous factor decreases and, accordingly, the accumulation of products of rock destruction - erosion and denudation by water and wind. Accumulative river terraces and floodplains, dunes and dunes are formed, composed of the corresponding types of continental
sediments (Table 20).
The main types of relief: flat, hilly and mountainous.
Flat relief consists of vast areas of land with flat
or a slightly undulating surface, within which height fluctuations do not exceed 0 ... 200 m.
Among the plains, their groups are distinguished depending on:
– positions above sea level of the plain are negative (depressions, depressions) such as the Caspian lowland, low-lying (up to 200 m) – West Siberian lowland, elevated (200...500 m) – Russian plain and plateau (more than 500 m) – Central Siberian plateau;
– depths and degrees of relief dissection (assessment is made by height fluctuations over 2 km): weakly dissected (height fluctuations up to 10 m), finely dissected (height fluctuations up to 25 m), roughly dissected (height fluctuations up to 200 m);
– on the shape of the earth’s surface: horizontal, inclined, concave and convex.
Absolute marks and dissected relief are a consequence (result), first of all, of the latest (Neogene-Quaternary) vertical movements associated with horizontal movements. The origin of plains is structural, accumulative and sculptural. Structural (primary, platform) plains formed on the site of platform sections of the earth's crust. They have a cover of quietly lying layers of sedimentary or consonant bodies of igneous rocks (Caspian, West Siberian lowlands, Central Siberian table plain).
Accumulative plains have not only a platform sedimentary cover of almost horizontally occurring marine sediments, but also continental - alluvial, glacial moraine, aeolian and other sediments that arose due to exogenous processes. For example, on the East European Plain, Quaternary glacial deposits are very widespread: moraine , fluvioglacial or limnic, which have a large thickness - tens to hundreds of meters. These deposits are dominated by alternating layers of sand and clay, which make up various hills and ridges called kamas , drumlinamioses. Within such forms of relief and sediments, builders carry out their activities, who must take into account the possibility of modern exogenous processes occurring on such areas of the earth’s surface, primarily landslides and water erosion. The East European Plain is classified as primary (on a platform cover). In the foothills and intermountain troughs (on a folded foundation), sloping plains arise due to the accumulation of alluvial, deluvial-proluvial, and sometimes mudflow deposits.
Sculptural plains arise, as a rule, at the site of the destruction of ancient mountains, leveling the primary surface through the processes of denudation and abrasion. Abrasion plains are formed as a result of the destruction of coasts by sea waves. A denudation plain is an area of land with a folded foundation lying close to the earth's surface, i.e. the emergence to the surface of intrusive, metamorphic and sedimentary rocks, crushed into folds and penetrated by various faults. The most striking example is Za - Ural plain, located east of the Ilmen and Vishnevye mountains and spurs of the Uraltau ridge, and occupying most of the territory of the Chelyabinsk region. It was formed during the Meso-Cenozoic due to the destruction of the Paleozoic Ural Mountains, denudation of terrigenous sediments, as well as the abrasion activity of the West Siberian Sea, into which all clastic sediments were carried. Since the Trans-Ural Plain was formed due to two important exogenous processes, it is more correct to call it abrasion-denudation. The Kazakh small hills also belong to the denudation plains.
Hilly terrain is characterized by alternating hills with relative heights of no more than 200 m and low areas in the form of hollows. The mountainous terrain is an alternation of large elevations in the form of mountains and ridges more than 200 m high and depressions in the form of valleys, depressions and basins. Depending on the absolute elevations and the relative excess of 2 km in length, mountainous reliefs are divided into high, medium-altitude and low. High mountains have absolute elevations of more than 2000 m with a relative elevation of 1000 m along lines perpendicular to the direction of the river valleys. Medium-altitude mountains have absolute elevations of 700...2000 m and a relative incision depth of 500...700 m. Low mountains have absolute elevations of 700...800 m and a depth of dissection of 150...450 m. The slopes are usually gentle. Based on their origin, they are classified as tectonic, volcanic and erosive.
Tectonic mountains were formed as a result of complex tectonic movements (horizontal and associated vertical movements). They occupy most of the territories of the Cenozoic mountain-fold regions (the mountains of Kamchatka, Sakhalin, the Caucasus), as well as certain territories of ancient mountain-fold regions. At the base of the Southern Urals lies the Ural Paleozoic mountain-fold region; the mountains were preserved only to the west of the Trans-Ural Plain, where individual blocks of the earth’s crust, as a result of recent and modern vertical movements, had the highest rates (up to 8 mm/year) and amplitudes (up to 1000 m) of uplifts. Mountains that were revived due to the uplift of individual blocks of folded areas in Neogene-Quaternary times are classified as block mountains.
Volcanic mountains arose as a result of volcanic activity and were preserved in areas of Alpine (Cenozoic) folding, as in Kamchatka, in the Alps, or in zones of modern mid-ocean ridges and rift zones, such as Mount Kilimanjaro.
Erosion mountains are formed as a result of the erosional dismemberment of ancient structural and accumulative plains due to the Neogene-Quaternary uplifts of these blocks above the erosion base. An example of such mountains is the Putorana plateau (elevations up to 1700 m) on the Central Siberian Plateau.
Relief- a set of irregularities on the earth's surface.
The relief is made up of positive (convex) and negative (concave) shapes. The largest negative forms relief on Earth - ocean depressions, positive - continents. These are first order landforms. Landforms second order - mountains and plains (both on land and at the bottom of the oceans). The surface of the mountains and plains has a complex topography consisting of smaller forms.
Morphological structures- large elements of the relief of land, the bottom of oceans and seas, the leading role in the formation of which belongs to endogenous processes . The largest irregularities in the Earth's surface form continental protrusions and ocean trenches. The largest elements of land relief are flat-platform and mountainous areas.
Plain-platform areas include the flat parts of ancient and young platforms and occupy about 64% of the land area. Among the flat-platform areas there are low , with absolute heights of 100-300 m (East European, West Siberian, Turanian, North American plains), and high , raised by recent crustal movements to a height of 400-1000 m (Central Siberian Plateau, African-Arabian, Hindustan, significant parts of the Australian and South American plain regions).
Mountain areas occupy about 36% of the land area.
The underwater edge of the continent (about 14% of the Earth's surface) includes a generally shallow flat strip of continental shallows (shelf), a continental slope and a continental foot located at depths from 2500 to 6000 m. The continental slope and continental foot separate the continental protrusions, formed by the combination of land and shelf, from the main part of the ocean floor, called the ocean floor.
Island arc zone - transition zone of the ocean floor. The ocean floor itself (about 40% of the Earth's surface) is mostly occupied by deep-sea (average depth 3-4 thousand m) plains that correspond to oceanic platforms.
Morphosculptures- elements of the relief of the earth's surface, in the formation of which the leading role belongs exogenous processes . The work of rivers and temporary streams plays the greatest role in the formation of morphosculptures. They create widespread fluvial (erosive and accumulative) forms (river valleys, ravines, ravines, etc.). Glacial forms are widespread, caused by the activity of modern and ancient glaciers, especially the cover type (northern part of Eurasia and North America). They are represented by valleys, “ram’s foreheads” and “curly” rocks, moraine ridges, eskers, etc. In the vast territories of Asia and North America, where permafrost strata are common, various forms of frozen (cryogenic) relief are developed.
The most important landforms.
The largest landforms are continental ridges and ocean basins. Their distribution depends on the presence of a granite layer in the earth's crust.
The main landforms are mountains And plains . Approximately 60% of the land area is plains- vast areas of the earth's surface with relatively small (up to 200 m) fluctuations in heights. Based on absolute height, the plains are divided into lowlands (height 0-200 m), hills (200-500 m) and plateaus (above 500 m). According to the nature of the surface - flat, hilly, stepped.
Table “Relief and landforms. Plains."
Mountains- elevations of the earth's surface (more than 200 m) with clearly defined slopes, base, and top. Based on their appearance, mountains are divided into mountain ranges, chains, ridges and mountainous countries. Free-standing mountains are rare, representing either volcanoes or the remains of ancient destroyed mountains. Morphological mountain elements are: base (sole); slopes; peak or ridge (at ridges).
Foot of the mountain- this is the border between its slopes and the surrounding area, and it is expressed quite clearly. With a gradual transition from the plain to the mountains, a strip is distinguished, which is called the foothills.
Slopes occupy most of the surface of the mountains and are extremely varied in appearance and steepness.
Vertex- the highest point of a mountain (mountain ranges), the pointed top of a mountain - a peak.
Mountain countries(mountain systems) - large mountain structures that consist of mountain ranges - linearly elongated mountain uplifts intersecting slopes. The points of connection and intersection of mountain ranges form mountain nodes. These are usually the highest parts of mountainous countries. The depression between two mountain ranges is called a mountain valley.
Highlands- areas of mountainous countries, consisting of heavily destroyed ridges and high plains covered with destruction products.
Table “Relief and landforms. Mountains"
By height, mountains are divided into low (up to 1000 m), medium high (1000-2000 m), high (more than 2000 m). Based on their structure, folded, folded-block and block mountains are distinguished. Based on their geomorphological age, they distinguish between young, rejuvenated and revived mountains. Mountains of tectonic origin predominate on land, while mountains of volcanic origin predominate in the oceans.
Volcano(from Latin vulcanus - fire, flame) - a geological formation that arises above channels and cracks in the earth's crust, through which lava, ash, flammable gases, water vapor and rock fragments erupt onto the earth's surface. Highlight active, asleep Andextinct volcanoes. The volcano consists of four main parts : magma chamber, vent, cone and crater. There are about 600 volcanoes around the world. Most of them are located along plate boundaries, where red-hot magma rises from the Earth's interior and bursts to the surface.
Hello dear readers! Today I would like to talk about what the main landforms are. So shall we begin?
Relief(French relief, from the Latin relevo - I lift) is a set of irregularities of land, the bottom of seas and oceans, varying in contours, sizes, origins, age and history of development.
Consists of positive (convex) and negative (concave) shapes. The relief is formed mainly due to the long-term simultaneous influence of endogenous (internal) and exogenous (external) processes on the earth's surface.
The basic structure of the earth's relief is created by forces that lurk deep in the bowels of the Earth. Day after day, external processes influence it, tirelessly modifying it, cutting deep valleys and smoothing mountains.
Geomorphology – is the science of changes in the earth's topography. Geologists know that the old epithet “eternal mountains” is far from true.
Mountains (you can read more about mountains and their types) are not at all eternal, even though the geological time of their formation and destruction can be measured in hundreds of millions of years.
In the mid-1700s, the Industrial Revolution began. And from that moment on, human activity plays an important role in transforming the face of the Earth, which sometimes leads to unexpected results.
The continents acquired their current place on the planet and their appearance as a result of tectonics, that is, the movement of geological plates that form the solid outer shell of the Earth.
The movements that are the most recent in time occurred within the last 200 million years - this includes the connection of India with the rest of Asia (more about this part of the world) and the formation of the Atlantic Ocean depression.
Our planet has undergone many other changes throughout its history. The result of all these convergences and divergences of huge massifs and movements were numerous folds and faults of the earth's crust (more detailed information about the earth's crust), as well as powerful piles of rocks from which mountain systems were formed.
I will give you 3 striking examples of recent mountain building or orogenesis, as geologists call it. As a result of the collision of the European plate with the African plate, the Alps emerged. When Asia collided with India, the Himalayas soared to the skies.
The Andes pushed upward the shift of the Antarctic Plate and the Nazca Plate, which together form part of the Pacific Trench, under the plate on which South America rests.
These mountain systems are all relatively young. Their sharp outlines did not have time to soften those chemical and physical processes that continue to change the earth’s appearance today.
Earthquakes cause enormous damage and rarely have long-term consequences. But volcanic activity injects fresh rocks into the earth’s crust from the depths of the mantle, often noticeably changing the usual appearance of the mountains.
Basic landforms.
Within the landmass, the earth's crust consists of a variety of tectonic structures that are more or less separated from one another, and differ from adjacent areas in geological structure, composition, origin and age of rocks.
Each tectonic structure is characterized by a certain history of movements of the earth’s crust, its intensity, regime, accumulation, manifestations of volcanism and other features.
The nature of the relief of the Earth's surface is closely related to these tectonic structures, and to the composition of the rocks that form them.
Therefore, the most important regions of the Earth with a uniform topography and a close history of their development - the so-called morphostructural regions - directly reflect the main tectonic structural elements of the earth's crust.
Processes on the earth's surface that affect the main forms of relief formed by internal, that is, endogenous processes, are also closely related to geological structures.
Individual details of large relief forms form external, or exogenous, processes, weakening or strengthening the action of endogenous forces.
These details of large morphostructures are called morphosculptures. Based on the scope of tectonic movements, their nature and activity, two groups of geological structures are distinguished: moving orogenic belts and persistent platforms.
They also differ in the thickness of the earth’s crust, its structure and the history of geological development. Their relief is also different - they have different morphostructures.
Flat areas of various types with small relief amplitudes are characteristic of platforms. The plains are divided into high (Brazilian - 400-1000 m absolute height, that is, altitude above sea level, African) and low (Russian Plain - 100-200 m absolute height, West Siberian Plain).
More than half of the total land area is occupied by the morphostructures of platform plains. Such plains are characterized by complex relief, the forms of which were formed during the destruction of heights and the redeposition of materials from their destruction.
Over large expanses of plains, as a rule, the same layers of rocks are exposed, and this causes the appearance of a homogeneous relief.
Among the platform plains, young and ancient areas are distinguished. Young platforms can sag and are more mobile. Ancient platforms are characterized by rigidity: they fall or rise as one larger block.
4/5 of the surface of all land plains is part of such platforms. On the plains, endogenous processes manifest themselves in the form of weak vertical tectonic movements. The diversity of their relief is associated with surface processes.
Tectonic movements also influence us: in areas that rise, denudation, or destruction processes, predominate, and in areas that decline, accumulation, or accumulation, predominates.
External, or exogenous, processes are closely related to the climatic features of the area - the work of the wind (aeolian processes), erosion by flowing waters (erosion), the solvent action of groundwater (more about groundwater) (karst), washing away by rainwater (deluvial processes) and others .
The relief of mountainous countries corresponds to orogenic belts. Mountainous countries occupy more than a third of the land area. As a rule, the topography of these countries is complex, highly dissected and with large height amplitudes.
The different types of mountainous terrain depend on the rocks that compose them, on the height of the mountains, on the modern natural features of the area and on the geological history.
In mountainous countries with complex terrain, there are individual ridges, mountain ranges and various intermountain depressions. Mountains are formed by bent and tilted layers of rock.
Strongly bent into folds, crushed rocks alternate with igneous crystalline rocks in which there is no layering (basalt, liparite, granite, andesite, etc.).
Mountains arose in places on the earth's surface that were subject to intense tectonic uplift. This process was accompanied by the collapse of layers of sedimentary rocks. They tore, cracked, bent, compacted.
From the depths of the Earth, magma rose through gaps, which cooled at depth or poured out to the surface. Earthquakes occurred repeatedly.
The formation of large landforms - lowlands, plains, mountain ranges - is primarily associated with deep geological processes that have shaped the earth's surface throughout geological history.
During various exogenous processes, numerous and varied sculptural or small relief forms are formed - terraces, river valleys, karst chasms, etc...
For the practical activities of people, the study of large landforms of the Earth, their dynamics and various processes that change the surface of the Earth is very important.
Weathering of rocks.
The earth's crust consists of rocks. Softer substances, called soils, are also formed from them.
A process called weathering is the primary process that changes the appearance of rocks. It occurs under the influence of atmospheric processes.
There are 2 forms of weathering: chemical, in which it decomposes, and mechanical, in which it crumbles into pieces.
Rock formation occurs under high pressure. As a result of cooling, deep in the bowels of the Earth, molten magma forms volcanic rocks. And at the bottom of the seas, sedimentary rocks are formed from rock fragments, organic remains and silt deposits.
Exposure to weather.
Multilayer horizontal strata and cracks are often found in rocks. They eventually rise to the surface of the earth, where the pressure is much lower. The stone expands as the pressure decreases, and all the cracks in it accordingly.
Stone is easily exposed to weather factors due to naturally formed cracks, bedding and joints. For example, water that has frozen in a crack expands, pushing its edges apart. This process is called frost wedging.
The action of plant roots, which grow in cracks and, like wedges, push them apart, can be called mechanical weathering.
Chemical weathering occurs through the mediation of water. Water flowing over the surface or soaking into the rock carries chemicals into it. For example, oxygen in water reacts with iron contained in the rock.
Carbon dioxide absorbed from the air is present in rainwater. It forms carbonic acid. This weak acid dissolves limestone. With its help, the characteristic karst terrain, which gets its name from the area in Yugoslavia, is formed, as well as huge labyrinths of underground caves.
Many minerals dissolve with the help of water. And minerals, in turn, react with rocks and decompose them. Atmospheric salts and acids also play an important role in this process.
Erosion.
Erosion is the destruction of rocks by ice, sea, water flows or wind. Of all the processes that change the earth's appearance, we know it best.
River erosion is a combination of chemical and mechanical processes. Water not only moves rocks, and even huge boulders, but, as we have seen, dissolves their chemical components.
Rivers (more about rivers) erode floodplains, carrying soil far into the ocean. There it settles to the bottom, eventually turning into sedimentary rocks. The sea (you can talk about what the sea is) is constantly and tirelessly working to remake the coastline. In some places it builds up something, and in others it cuts something off.
The wind carries small particles like sand over incredibly long distances. For example, in southern England the wind brings sand from the Sahara from time to time, covering the roofs of houses and cars with a thin layer of reddish dust.
Impact of gravity.
Gravity during landslides causes hard rocks to slide down the slope, changing the terrain. As a result of weathering, rock fragments are formed, which make up the bulk of the landslide. Water acts as a lubricant, reducing friction between particles.
Landslides sometimes move slowly, but sometimes they rush at a speed of 100 m/sec or more. A creep is the slowest landslide. Such a landslide creeps only a few centimeters per year. And only after a few years, when trees, fences and walls bow under the pressure of the load-bearing earth, will it be possible to notice it.
A mudflow or mud flow can cause clay or soil (more about soil) to become oversaturated with water. It happens that for years the earth remains firmly in place, but a small earthquake is enough to bring it down the slope.
In a number of recent disasters, such as the eruption of Mount Pinatubo in the Philippines in June 1991, the main cause of casualties and destruction was mud flows that flooded many houses to the very roof.
As a result of avalanches (stone, snow, or both), similar disasters occur. A landslide or mud slide is the most common form of landslide.
On a steep bank, which is washed away by a river, where a layer of soil has broken away from the base, you can sometimes see traces of a landslide. A large landslide can lead to significant changes in the terrain.
Rockfalls are common on steep rocky slopes, deep gorges or mountains, especially in areas where eroded or soft rocks predominate.
The mass that has slid down forms a gentle slope at the foot of the mountain. Many mountain slopes are covered with long tongues of crushed stone scree.
Ice Ages.
Centuries-long climate fluctuations also led to significant changes in the earth's topography.
During the last ice age, the polar ice caps held enormous masses of water. The northern cap extended far to the south of North America and the European continent.
Ice covered about 30% of the land on Earth (compared to only 10% today). Sea levels during the Ice Age (more information about the Ice Age) were about 80 meters lower than they are today.
The ice melted, and this led to colossal changes in the relief of the Earth's surface. For example, the following: the Bering Strait appeared between Alaska and Siberia, Great Britain and Ireland turned out to be islands that were separated from the whole of Europe, the land area between New Guinea and Australia went under water.
Glaciers.
In the ice-covered subpolar regions and in the highlands of the planet, there are glaciers (more about glaciers) - ice rivers. The glaciers of Antarctica and Greenland annually dump huge masses of ice into the ocean (you can learn more about what the ocean is), forming icebergs that pose a danger to shipping.
During the Ice Age, glaciers played a major role in giving the relief of the northern regions of the Earth a familiar appearance.
Crawling along the earth's surface with a giant planer, they carved out depressions in valleys and cut off mountains.
Under the weight of glaciers, old mountains, such as those in northern Scotland, have lost their sharp outlines and former height.
In many places, glaciers have completely cut away multi-meter layers of rock that had accumulated over millions of years.
The glacier, as it moves, captures a lot of rock fragments into the so-called accumulation area.
Not only stones fall there, but also water in the form of snow, which turns into ice and forms the body of the glacier.
Glacial sediments.
Having passed the boundary of the snow cover on the mountain slope, the glacier moves into the ablation zone, that is, gradual melting and erosion. The glacier, towards the end of this zone, begins to leave sediment of rocks on the ground. They are called moraines.
The place where the glacier finally melts and turns into an ordinary river is often designated as a terminal moraine.
Those places where long-vanished glaciers ended their existence can be found along such moraines.
Glaciers, like rivers, have a main channel and tributaries. The glacial tributary flows into the main channel from the side valley that it paved.
Usually its bottom is located above the bottom of the main channel. Glaciers that have completely melted leave behind a U-shaped main valley, as well as several side valleys, from which picturesque waterfalls cascade down.
You can often find such landscapes in the Alps. The clue to the driving force of the glacier lies in the presence of so-called erratic boulders. These are separate fragments of rock, different from the rocks of the glacial bed.
Lakes (more information about lakes) from a geological point of view are short-lived landforms. Over time, they are filled with sediment from the rivers that flow into them, their banks are destroyed and the water drains away.
Glaciers have formed countless lakes in North America, Europe (you can read more about this part of the world) and Asia by carving out hollows in rocks or blocking valleys with terminal moraines. There are a great many glacial lakes in Finland and Canada.
For example, other lakes, such as Crater Lake in Oregon (USA) (more about this country), are formed in the craters of extinct volcanoes as they fill with water.
Siberian Baikal and the Dead Sea, between Jordan and Israel, arose in deep cracks in the earth's crust that were formed by prehistoric earthquakes.
Anthropogenic landforms.
Through the work of builders and engineers, new relief forms are created. The Netherlands is a great example of this. The Dutch proudly say that they created their country with their own hands.
They were able to recapture about 40% of the territory from the sea, thanks to a powerful system of dams and canals. The need for hydroelectric power and fresh water has forced people to build a considerable number of artificial lakes or reservoirs.
In the state of Nevada (USA) there is Lake Mead, it was formed as a result of the damming of the Colorado River by the Hoover Dam.
After the construction of the high-rise Aswan Dam on the Nile, Lake Nasser appeared in 1968 (near the border of Sudan with Egypt).
The main purpose of this dam was to regularly provide water for agriculture and regulate annual floods.
Egypt has always suffered from changes in the level of Nile floods, and it was decided that a dam would help solve this centuries-old problem.
But on the other hand.
But the Aswan Dam is a striking example of the fact that nature is not to be trifled with: it will not tolerate rash actions.
The whole problem is that this dam blocks the annual deposits of fresh silt that fertilized the agricultural land, and in fact, which formed the Delta.
Now, silt is accumulating behind the wall of the Aswan High Dam, thereby threatening the existence of Lake Nasser. Significant changes can be expected in the Egyptian terrain.
The appearance of the Earth is given new features by railways and highways built by man, with their cut slopes and embankments, as well as mine waste heaps, which have long disfigured the landscape in some industrial countries.
Erosion is caused by cutting down trees and other plants (their root systems hold together mobile soils).
It was these ill-considered human actions that led, in the mid-1930s, to the emergence of the Dust Bowl on the Great Plains, and today they threaten the Amazon basin in South America.
Well, dear friends, that’s all for now. But expect new articles soon 😉 I hope that this article helped you understand what types of relief there are.
Relief(fr. relief, from lat. relevo- lift) - a set of irregularities of the solid earth's surface and other solid planetary bodies, varied in outline, size, origin, age and history of development. Composed of positive and negative forms. Relief is the object of study of geomorphology.
Mountain, hill - a convex cone-shaped landform that rises above the surrounding area. The highest point of a mountain or hill is called top . From the top there are slopes or 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 a hill, and more than 200 m with steep slopes is called a mountain. Mountains and hills are depicted as closed horizontal lines with berg strokes directed from the top to the bottom.
Basin (depression) is a relief form opposite to a mountain (hill), 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 into the surrounding area is called the edge. The basin, like the mountain, is depicted by closed horizontal lines, but the berghstrokes in this case are directed towards the bottom.
Ridge - an elongated hill that gradually decreases 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 extend in opposite directions, is called the watershed. The ridge is depicted by convex horizontal lines directed convexly towards the lower terrain.
Hollow– a depression 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 drainage line or thalweg. The varieties of hollow are: d Olina – a wide hollow with gentle slopes;
ravine– (in mountainous areas – gorge) – a narrow ravine with steep exposed slopes;
beams called larger than ravines, depressions with gentle slopes, often covered with vegetation.
The hollow is depicted by concave horizontal lines, concavity directed towards the lowering of the terrain; The steep slopes of the ravine are depicted with special symbols.
Saddle – a low area of terrain located on a ridge between neighboring peaks. 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.
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, ridges. The relief depicted
exactly as he was seen. For greater clarity, the mountains were covered with shadows. This method of depicting relief was widespread in the 15th-18th centuries. In on
Currently, this method is used on those maps where clarity is required, and not
accuracy, and therefore it is primarily used on children's cards.
2. 2. Line method.
Painting of the relief in the 18th century. Firstly
no longer satisfies the military, the main consumers of cards. They had to quickly
obtain from maps an accurate idea of the steepness of the slopes, roughness 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. scale was used. Bolotov and the scale of the General Staff. Prin
The principle for constructing such scales is as follows: the steeper the slope, the thicker and denser the shading,
at the same time, steep slopes are covered with shadow, and gentle slopes are highlighted (Fig. 5.14).
The disadvantage of this method is that it is impossible to determine absolute
altitude and relative heights. In addition, drawing strokes is very labor-intensive, and printing
Mapping requires advanced reproduction technology. Therefore, we began to look for new ways
relief images. Currently, this method is used when depicting rocks
detailed relief on topographic maps.
3. Relief washing method
(black and white plastic), i.e. creating a halftone iso
fermentation under a given area lighting. Washing is used to give volume
sty landforms.
On handwritten maps, hillshading was widely used already in the second half of the 18th century.
but its seal was mastered only in the middle XIX V. as a result of the introduction of lithography. Ori
The relief washing ginal is like a photograph of the relief model locally
sty with side north-west lighting
4 Method of elevation marks.
Elevations are abso signs signed on the map
Lute height marks of points. Using elevation marks, characteristic heights are shown
including you team,
having the greatest height from which the opportunity is realized
good overview of the area. The elevations of mountains, hills, mounds, passes,
ditches and ledges, embankments and recesses. They make it easier to read the map and make it possible to determine
determining the excess of some points over others.
5.
-
heights
solid
(carried out accordingly)
exactly the height of the section); thickened
additional
horizontal or half-burnt
umbrellas
auxiliary
horizontal
(carried out at a quarter of the height of the relief section).
6. Hypsometric method
or layer-by-layer painting of height steps, main and highest
a more commonly used method of depicting relief on physical and hypsometric maps.
Contour lines on survey maps are called isohypsum. Isohypses
serve as dividing
lines between height steps passing through a certain number of meters along
height. On hypsometric maps of Russia, a scale is used, which is based on the principle
tsipu: the higher, the darker
(Fig. 5.17).
10 image of the main forms of terrain with contour lines
Contour method. Horizontal
- this is a line connecting identical marks
heights
Contour lines are the main way to depict relief on topographic maps
(Fig. 5.16). There are the following types of contour lines: solid
(carried out accordingly)
exactly the height of the section); thickened
(with a section of 5.0 m and 20 m, every fifth th
horizontal, with a cross section of 2.5 m - every tenth); additional
horizontal or half-burnt
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 horizontal lines are supplemented with berg strokes (short lines perpendicular to
to horizontal lines indicating the direction of the slope), captions of absolute height marks
characteristic points of the terrain and some contour lines (marks are signed according to their
in ditches and the base of the numbers are always located down the slope). The main advantage
This method is that along horizontal lines you can carry out various cartometry
technical work: determine the absolute heights of points and the excess of some points over others
mi, steepness and direction of slopes, etc. According to the pattern of horizontal lines, their shape, density
information, you can get an idea of the terrain. Correctly selected height
This 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 used today on state surveys.
physical maps.
Contour properties
Properties of contour lines:
1. All points lying on the same horizontal line have the same elevation
2. Contour lines with different marks do not intersect
3. The steeper the slope, the smaller the distance between horizontal lines
Contour lines are marked at their break so that the lower part of the number faces the downward direction of the slope; berg strokes are used to determine the direction of the slope. Every fifth horizontal line is drawn with a thick line.
Height of the relief section (h)- they call the difference in elevations of adjacent horizontal lines - this is a constant value for a given drawing.
Horizontal distance between adjacent horizontal lines – laying of the slope (d) .
Slope (i) is tg of the terrain inclination angle ν or the ratio of the difference in heights of points to the horizontal distance between them.
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Lesson questions:
1. Types and forms of terrain. The essence of depicting relief on maps using contour lines. Types of contours. Depiction of typical relief forms by horizontal lines.
1.1 Types and forms of terrain.
In military affairs terrain understand the area of the earth's surface on which combat operations are to be conducted. Irregularities in the earth's surface are called terrain, and all objects located on it created by nature or human labor (rivers, settlements, roads, etc.) - local items.
Relief and local objects are the main topographical elements of the terrain that influence the organization and conduct of combat, the use of military equipment in combat, conditions of observation, firing, orientation, camouflage and maneuverability, i.e., determining its tactical properties.
A topographic map is an accurate representation of all the most tactically important elements of the terrain, plotted in a mutually precise location relative to each other. It makes it possible to explore any territory in a relatively short time. A preliminary study of the terrain and decision-making for a unit (unit, formation) to carry out a particular combat mission is usually carried out on a map, and then clarified on the ground.
The terrain, influencing combat operations, in one case can contribute to the success of troops, and in another have a negative impact. Combat practice convincingly shows that the same terrain can give greater 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 relatively low (up to 2°) slope 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 the degree of ruggedness. Its clayey, loamy, sandy loam, and peat soils allow the unimpeded movement of military equipment in dry weather and significantly complicate movement during the rainy season, spring and autumn thaw. It can be cut up by river beds, ravines and ravines, and have many lakes and swamps, which significantly limit the ability of troops to maneuver and reduce the pace of the offensive (Fig. 2).
Flat terrain is usually more favorable for organizing and conducting an offensive and less favorable for defense.
Hilly terrain characterized by the undulating nature of the earth's surface, forming unevenness (hills) with absolute heights of up to 500 m, relative elevations of 25 - 200 m and a predominant steepness of 2-3° (Fig. 3, 4). Hills are usually composed of hard rock, their tops and slopes are covered with a thick layer of loose rock. The depressions between the hills are wide, flat or closed basins.
Hilly terrain ensures the movement and deployment of troops hidden from enemy ground observation, facilitates the selection of places for firing positions of missile troops and artillery, and provides good conditions for the concentration of troops and military equipment. In general, it is favorable for both offense and defense.
Mountain landscape represents areas of the earth's surface that are significantly elevated above the surrounding area (with absolute heights of 500 m or more) (Fig. 5). It is distinguished by complex and varied terrain and specific natural conditions. The main forms of relief are mountains and mountain ranges with steep slopes, often turning into cliffs and rocky cliffs, as well as hollows and gorges located between mountain ranges. Mountainous terrain is characterized by sharply rugged terrain, the presence of inaccessible areas, a sparse network of roads, a limited number of settlements, rapid river flows with sharp fluctuations in water levels, a variety of climatic conditions, and the predominance of rocky soils.
Combat operations in mountainous areas are considered as actions under special conditions. Troops often have to use mountain passes, making observation and firing, orientation and target designation difficult, at the same time it contributes to the secrecy of the location and movement of troops, facilitates the installation of ambushes and engineering barriers, and the organization of camouflage.
1.2 The essence of depicting relief on maps using contour lines.
Relief is the most important element of the terrain, determining its tactical properties.
The image of the relief on topographic maps gives a complete and fairly detailed idea of the unevenness of the earth's surface, the shape and relative position, elevations and absolute heights of terrain points, the prevailing steepness and length of the slopes.
1.3 Types of contour lines.
Horizontal- a closed curved line on a map, which corresponds to a contour on the ground, all points of which are located at the same height above sea level.
The following horizontal lines are distinguished:
- basic(solid) - the relief section corresponding to the height;
- thickened - every fifth main horizontal line; stands out for ease of reading the relief;
- additional horizontal lines(semi-horizontals) - drawn by a broken line at a height of the relief section equal to half the main one;
- auxiliary - are depicted by short broken thin lines at an arbitrary height.
Distance between two adjacent main horizontal heights are called the height of the relief section. The height of the relief section is indicated on each sheet of the map under its scale. For example: “Continuous horizontal lines are drawn every 10 meters.”
To facilitate the calculation of contours when determining the heights of points on the map, all solid contours corresponding to the fifth multiple of the section height are drawn thickly and a number is placed on it indicating the height above sea level.
In order to quickly determine the nature of surface irregularities on maps when reading a map, special slope direction indicators are used - berg strokes- in the form of short lines placed on horizontal lines (perpendicular to them) in the direction of slopes. They are placed on the bends of horizontal 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 characteristic shapes 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 gaps between the main contour lines are very large (more than 3 - 4 cm on the map).
Auxiliary contours used to depict individual relief details (saucers in steppe regions, depressions, individual hillocks on flat terrain), which are not conveyed by the main or additional horizontal lines.
1.4 Representation of typical relief forms by horizontal lines.
Relief on topographic maps is depicted by curved closed lines connecting terrain points that have the same height above the level surface, taken as the beginning of the height reference. Such lines are called horizontals. The image of the relief with horizontal lines is supplemented by captions of absolute heights, characteristic points of the terrain, some horizontal lines, as well as numerical characteristics of relief details - height, depth or width (Fig. 7).
Some typical landforms on maps are displayed not only as main ones, but also as additional and auxiliary contour lines (Fig. 8).
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Rice. 8. Image of typical relief forms |
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2. Determination on the map of absolute heights and relative elevations of terrain points, ascents and descents, and steepness of slopes.
2.1. Determination of absolute heights and relative elevations of terrain points on the map
2.2. Identification on the map of ascents and descents along the route.
Rice. 10. Identification on the map of ascents and descents along the route (route profile).
Rice. eleven. Determining the steepness of the slopes on the map |
Profile- a drawing depicting a section of the terrain with a vertical plane.
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2.3.Determining the steepness of the slopes on the map.
The steepness of the slope on the map is determined by its position - the distance between two adjacent main or thickened horizontal lines; the lower the laying, the steeper the slope\.
To determine the steepness of the slope, you need to measure the distance between the horizontal lines with a compass, find the corresponding segment on the location graph and read the number of degrees (Fig. 11).
On steep slopes, this distance is measured between thickened horizontal lines 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 horizontal lines.
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Ice cliffs (barriers) and fossil ice outcrops (8 - cliff height in meters) |
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Turfed ledges (edges) not expressed as horizontal lines |
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Coastal, historical, etc. ramparts that are not expressed by horizontal lines (3 - height in meters) |
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1) Dry riverbeds in one line (less than 5 m wide); |
Elevation marks |
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Command heights |
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Elevation marks at landmarks |
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Main passes, their heights and duration |
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Passes, their heights and duration |
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Karst and thermokarst sinkholes not shown on map scale |
Potholes that are not expressed on the map scale |
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Holes expressed at map scale |
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Outlier rocks with landmark value (10-height in meters) |
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Outlier rocks that have no landmark value |
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Dikes and other narrow, steep-walled ridges of hard rock (5 - ridge height in meters) |
Craters of mud volcanoes |
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Volcano craters not shown on map scale |
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Mounds and mounds not shown on the map scale |
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Mounds and mounds expressed on the map scale (5 - height in meters) |
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Clusters of stones |
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Separately lying stones (3 - height in meters) |
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Entrances to caves and grottoes |
Notes
Military topography
Military ecology
Military medical training
Engineering training
Fire training
Fundamentals of external and internal ballistics. Hand grenades. Grenade launchers and rocket-propelled anti-tank grenades.