Earth's surface- this is land and the oceans. The continent consists of separate continents, or islands. Continents and individual large territories have different heights above sea level. Landforms earth's surface formed as a result of the interaction of internal (endogenous) and external (exogenous) processes of the Earth. Internal processes create huge unevenness, external processes smooth them out.
Over millions of years, water, wind and sun manage to almost completely destroy mountains, creating plains in their place and filling large depressions with destroyed material. Internal and external forces act simultaneously.
The largest planetary landforms are continents and ocean basins. The surface of each of them is uneven. Within their boundaries, there are two main landforms: plains and mountains. Plains are equal or hilly large expanses of land and ocean floor in which the heights of neighboring points differ little from each other. Mountains are areas of the earth's surface that are raised high above the surrounding area and have a highly dissected topography. At the bottom of the ocean there is special shape relief that is absent on the continents - deep-sea trenches caused by the imposition of an oceanic lithospheric plate under the continental one.
Small landforms formed by external forces - solar energy, gravity, the activity of surface waters, winds, glaciers, living organisms. These include ravines, ravines, river valleys, dunes, dunes, eskers, kamas, drumlins, etc.
Land relief very diverse. Mountains and land plains are distinguished according to different criteria: by height above sea level, by method of formation and age, by appearance.
Mountains There are: low - with an absolute height of up to 1000 m (Crimean), medium - from 1000 to 2000 m (Carpathians, Scandinavian), high - above 2000 m (Caucasus, Himalayas, Pamirs, Andes). On physical map they are indicated by light brown, brown and dark brown, respectively.
Plains are divided into: lowlands (their absolute height does not exceed 200 m above the level of the World Ocean. For example, the Black Sea, Amazonian), hills (from 200 to 500 m, in particular the Dnieper, Volyn, Podolsk) and plateaus (more than 500 m, for example, Central Siberian, Arabian).
On the map, the plains are indicated in green, yellow, and brown colors, respectively. If the plain lies below sea level, it is colored dark green on the map (for example, the Caspian Lowland).
Based on their formation, mountains are divided into folded (Giri is formed by the collision of two continental lithospheric plates), volcanic (arises as a result of the process of volcanism) and folded-Brish (ancient destroyed mountains).
Plains By education they are divided into primary and secondary. Due to age-related vertical movements of the lithosphere, individual coastal areas of the seas and oceans rose, forming vast lowlands (Black Sea, Western). Such plains are called primary. Other plains were formed in place of former mountains that collapsed over hundreds of millions of years (Eastern Plain). Some plains were formed by river sediments (Amazonian, Mesopotamian, Indo-Gangetic). Such plains are called secondary.
In appearance, there are flat plains with flat surface(Black Sea, Western) and hilly, on which hills alternate with basins and ravines. Such small forms of relief are characteristic of the plains of Ukraine.
Mountains are divided into individual peaks, mountain ranges consisting of interconnected mountains, as well as mountain valleys - depressions between mountain ranges. Narrow, deep mountain valleys are called mountain gorges.
The mountains with pointed peaks are high, according to the age of young people. Mountain gorges often form in them. Such mountains include the Caucasus, the Andes, the Pamirs, the Himalayas with the highest peak in the world, Chomolungma (Everest) - 8850 g.
Mountains with rounded tops are made of soft rocks, therefore they have smoothed, soft outlines of mountain ranges, similar to waves. Mountain valleys are shallow, mostly with gentle slopes. These mountains are medium and low in height. For example, the Ukrainian Carpathians, the highest peak of which is Hoverla - 2061 m, are medium-height mountains. There are mountains with flat tops. The slopes of these mountains are rapid or stepped. In Ukraine, such mountains include the Crimean ones.
Landforms are closely related to the structural features of the lithosphere. Sections of the lithosphere that differ in age, structure and mobility are called tectonic structures. Their main types are platforms (relatively stable sections of the lithosphere) and fold belts (moving parts of the lithosphere). Each platform consists of a crystalline basement and a sedimentary cover. The age of the platform is determined by the time of formation of its foundation. Based on age, platforms are divided into ancient Precambrian ones (with a foundation several billion years old) and young Late Paleozoic ones (their age is hundreds of millions of years old). On ancient platforms, sometimes the foundation reaches the surface and shields are formed. Outside them, where the sedimentary cover covers the foundation, there are slabs. Young platforms have a very thick sedimentary cover (several kilometers thick).
Folding belts were formed during different eras of mountain building. The most ancient was the Baikal era of mountain building (in the late Proterozoic), it was changed by the Caledonian (in the early Paleozoic) and the Hercynian (in the late Paleozoic). The mountains formed at this time are old, destroyed, blocky, usually low buildings. A consequence of the Mesozoic era of mountain building are folding belts of average age. Mountains of this age are very blocky and of medium altitude. In the Cenozoic era, the Alpine era of mountain building continues, as a rule, high folded mountains with pointed peaks are formed.
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) for the most part 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.
Typical volcano is a hill with a pipe passing through its thickness, called a volcanic vent with a magma chamber (an area of magma accumulation), from which the vent rises. In addition to the vent, small channels with magma, called mudflows and dikes, can also extend from the magma chamber. When a magma chamber is created high pressure, a mixture of magma and hard stones - lava - rises up the vent and is thrown into the air. This phenomenon is called volcanic eruption . If the lava is very thick, it can solidify in the crater of a volcano, forming a plug. However, enormous pressure from below bursts the plug, spewing large chunks of rock called volcanic bombs high into the air. After each volcanic eruption, the lava hardens into a hard crust. Volcanic hills with steep slopes are called conical, while those with gentle slopes are called shield hills. Modern active volcanoes: Klyuchevskaya Sopka, Avachinskaya Sopka (Kamchatka, Russia), Izalko (El Salvador), MaunaLoa (Hawaii), etc.
Lesson summary "Relief and landforms." Next topic:
The totality of the irregularities of the earth's surface form it relief. Landforms vary in size, origin, and development history. The relief of the earth, or more correctly, the earth's surface, is the result of a complex interaction of internal and external forces. Internal forces, the energy of which is provided by the internal energy of the Earth itself, create large irregularities. External forces smooth out these irregularities, creating smaller irregularities.
The largest landforms of the Earth- ridges of continents and depressions of oceans. Their distribution is determined by the structure earth's crust– the presence or absence of a granite layer. There are currently six continents on Earth. Land on the Earth's surface is distributed unevenly. We can distinguish two conventional hemispheres on the planet - oceanic and continental. In the center of the first is the Pacific Ocean, in the center of the second is Africa. The prevailing heights within the land are about 800 m, the average depths of the ocean are about 3500 m. The surface of the land and the ocean bottom is complicated by lower-order irregularities.
The main landforms are mountains and plains. About 60% of the land surface is occupied plains. These are vast areas of the earth's surface with small fluctuations in heights (about 200 m), relatively low elevated above sea level. According to absolute height, the plains are divided on lowlands (height from 0 to 200 m), hills (200-500 m) and plateaus (above 500 m). By the nature of the surface- flat, hilly and stepped. Lowland areas are the most populated and developed by people. Most cities and transport routes and the main tracts of cultivated land are concentrated on them.
They call them mountains distinct elevations on the earth's surface with heights of more than 200 m, with well-defined slopes and bases. Mountainous regions occupy about 40% of the land surface. Most of the mountains on Earth stretch in mutually perpendicular directions, close to sublatitudinal or submeridional. By height, mountains are divided into low (with altitudes up to 1000 m), medium altitude (1000-2000 m) and high (over 2000 m). According to the structure of mountains there are folded, folded - blocky and blocky. According to geomorphological age, they distinguish young, rejuvenated and reborn mountains. Mountains of tectonic origin predominate on land, while mountains of volcanic origin predominate in the oceans.
Within the land, the distribution of mountainous and lowland areas is determined by the structure of the earth's crust. On the platforms, due to the horizontal occurrence of rocks, there are plains. In folded areas, rocks lie in the form of folds, and in the relief they correspond to mountains.
The structure of the earth's crust determines not only the relief, but also the placement of mineral resources. Minerals of sedimentary origin (oil, gas, coal, salts) are concentrated in the sedimentary rocks of the platform cover. Minerals of igneous origin - in folded areas and crystalline platform basements. The greatest variety of minerals is characteristic of ancient platforms.
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They change quite quickly (a small ravine can appear in a few months), larger forms change slowly, over centuries. There are, however, factors (such as landslides) that can change the relief: mountains and crevasses appear, and the directions of rivers change. In the summer of 2007, one of these events did not occur: a landslide destroyed a unique geographical formation - a valley of geysers.
The relief changes under the influence of two types of factors: exogenous and endogenous. Endogenous (internal) factors: movements of the earth's crust, volcanic eruptions are discussed in detail in the relevant sections. Exogenous factors include: the destructive activity of wind and water, heat, flora and fauna.
Water has a serious impact on the terrain. It erodes rocks, forming ravines, washing away entire hills, and washing away rocks, which can then collapse. Rivers can become fuller and lay a new channel, or they can become shallow, and then land areas remain in place of water. All these are changes in relief. In addition, water interacts with rock substances, changing their composition and structure, which can lead to changes in relief.
The wind is especially active where there are no dense growths of plants. The wind blows away small rock particles and carries them to other areas, where they are deposited, retained by water or plants.
Many rocks are destroyed by heat. Either heating up or cooling back, they constantly expand and contract again. This leads to the destruction of bonds between the molecules of the substance, and the rocks crack.
Plants and animals also influence the formation of relief, some more strongly, others less. Plant roots destroy dense rocks and at the same time strengthen looser ones. Microorganisms change the structure of the soil, which can also lead to changes in topography. Animals that build dams on rivers and streams, in particular beavers, have a huge impact on the relief.
Basic landforms
- Plains are flat or hilly areas of land with a fairly large area. The plains differ in absolute height (above sea level):
- Lowlands, height does not exceed 200 m.
- Hills, height from 200 to 500 m.
- Plateau, altitude more than 500 m.
- A plateau is a specific landform with a flat top and steep edges, and can reach 3 km.
Plains- more stable areas of the earth's surface, they are less likely to occur, lowland rivers are calmer, and the relief changes much more slowly.
Mountains- areas of land rising to a height of more than 500 m, with a certain peak and steep slopes.
Mountains can form ridges and highlands. A ridge is a group of mountains, apparently elongated in a certain direction and with a slight difference in height. Famous mountain ranges.
As we already know, the earth's crust is mobile.
And this movement is determined by the movement of the mantle substance. As a result of such movement, mountains, ocean basins, and island arcs appear in the most mobile parts of the earth's crust. Stable areas of the earth's crust are characterized by flat surfaces. We call all this the relief of the Earth.
Continents and oceans- the main, largest landforms of the Earth. Their formation is due to tectonic, cosmic and planetary processes.
The mainland (continent) is the largest massif of the earth's crust, which has a three-layer structure: a sedimentary layer, a “granite” layer and a “basalt” layer. The average thickness of the continental crust is 35-45 km. Most of the continent's surface protrudes above the level of the World Ocean. In the modern geological era, there are six continents: Eurasia, Africa, North America, South America, Australia, Antarctica.
The world ocean is a continuous body of water surrounding the continents. The world's oceans are divided by continents into four oceans: the Pacific, Atlantic, Indian and Arctic. Land accounts for only 29% of the Earth's area. Everything else is the World Ocean.
Mountains and plains, as well as continents and oceans, are the main landforms of the Earth. Mountains are formed as a result of tectonic processes in zones of active tectonic activity, and plains are formed in areas that are little susceptible to mountain-forming processes.
Plains- large areas with flat or hilly surfaces. They vary in height. An example of a lowland is the Amazon lowland - the largest on Earth. It happens that lowlands are located below sea level - these are depressions. The Caspian lowland is located 28 m below sea level. At an altitude of 200-500 m above sea level there are hills, for example Central Russian, and above 500 m there are plateaus. An example of such a plain is the Central Siberian Plateau.
Mountains- areas of the earth's surface elevated above sea level to a height of more than 500 m. Mountains are considered low if their height is from 500 to 1000 m; medium - from 1000 to 2000 m and high - over 2000 m. The highest mountain on Earth - Chomolungma (Everest) has a height of 8848 m. You can determine the height of the mountains from a physical map, using an altitude scale.
Mountains differ not only in height, but also in shape. A linearly elongated group of mountains is called a mountain range. The Caucasus Mountains have this shape.
There are also mountain belts (Andean belt), mountain systems (the mountain system of Southern Siberia) and mountainous countries. The Pamirs are an example of a mountainous country.
Mountains and plains are located both on continents and in oceans. An example of mountains in the ocean are mid-ocean ridges.
Relief of the Earth- the result of the struggle between internal and external forces. The internal forces of the Earth form large relief forms: continents and oceans, mountains and plains. They not only form them, but also change and destroy them. External forces work constantly and slowly. They also destroy mountain ranges, fill up deep depressions, form hills, valleys, gullies, ravines, form river beds, that is, they form smaller landforms.
The destruction and change of rocks under the influence of fluctuations in air temperature, moisture and living organisms is called weathering.
Here are some examples of weathering. In the mountains these are landslides, landslides, mudflows, rockfalls, deep gorges cut by mountain rivers, moraine deposits of glaciers. For plains, typical examples of weathering are ravines and river valleys.