§ 23. External processes (textbook)

§ 23. External processes


1. Remember lessons from naturalWhat is called weathering.

2. As the Earth's surface can change the internal processes?


Concept of external processes. Earth's surface is formed not only internal processes, but also external. These include weathering, wind action, surface and groundwater, the sea ice. These processes, unlike domestic occurring on the surface or upper crust.

Differ and external processes that derive no energy inside the planet, and outside. They "use" energy of the Sun (Solar heat) force gravityVital functions organisms. At first glance, these forces seem much weaker. However, this just seems no wonder they say: "Water stone sharpens. External processes perform both destructive and creative work. Often referred to as sculptors surface. They cut through, obtochuyut, grind monoliths formed internal processes.

Detritus. It covers Nearly the entire surface of the planet and is the most common of all external processes. There are physical, chemical and organic weathering.

Physical weathering - A fracture of rocks to rubble under impact of sharp fluctuations in temperature and water freezing in cracks. Especially it actively occurs where significant contrasts of daily temperatures - in deserts and mountains. For example, Karakum Desert sand temperature and rocks during the day reached 80 0C, and night fell almost to 0 0S. Multiple heating and cooling leads to rapid cracking species. Destructive effect of frozen water in polar areas extended. Water, Freezing, known to increase in volume and expanding cracks. Subsequently, a solid block falls to pieces.

Chemical detritus- A fracture of rocks under the action of air, water and dissolved in it substances. They can eat away the rock, thus forming new minerals are and breed. Yes, hard feldspar into a soft clay. Most intense chemical weathering occurs in areas with humid and warm climate.

Organic detritus- A rock failure organisms. Often it is starting to bacteria mosses and lichens, which settled on the rocks. The roots of plants, getting into crack rocks, also contribute to cracking. Among the animals significantly affect digging for rocks, rain worms, ants and others.

Because of weathering formed loose sediments that are easy to disperse and winds blurred flowing water.


Fig. Physical detritus


Fig. Organic weathering. Moss, who settled on the rocks every second are destructive work


Work wind. Wind has three types of work: destructive, transport and creative. Destructive work turns in blowing loose and demystification rocks. Wind can blow huge mass of rocks and soil. For example, U.S. during a storm in 1934 only One day was demolished 300 million tons of soil. Winds picked up sand on the cliff vdaryayutsya and obtochuyut, grind stone appearances. As a result, not only formed scratches, but weird sculptural forms. Often they resemble pillars mushrooms, figures of people and so on. They are called outliers. Chimeric outliers, for example, form Ghost Valley on mountain array Demerdzhi in the Crimea.

Transport workis moving in the wind debris species over long distances. So, Widespread in 1926 a storm from the south of Ukraine brought the dust and hornozem even to the Baltic Sea.

Creative work wind - a delaying the formation of fragments and transferred  various Eolian Forms surface (by name mythical ancient Greek god of winds Eola). Wherever there is sand formed ripple - Fine sand rollers, combined in chains. At Sea coast, in river valleys wind nahortaye Dunes - sand mounds 10-20 m, rarely -100 m. In Ukraine, they are common in Dnieper River valleyOn the Black and Azov Seas. In sandy deserts formed dunes - Mounds of sand 70-150 m tall as a crescent. Their many Sahara Kyzylkum, Karakum. Dunes and dunes, wind-blown, constantly moves per year can "take" hundreds of meters. In the history of known cases of assault by sands Libyan Desert were completely two cities filled Egypt.


Fig. Outliers in Desert


Fig. Dune, dunes, ripples

Work waters. Surface water - Temporary (which formed after heavy rains or melting snow) and regular (river) flows - carry a great job and changing surface. Destructive work surface water is washing out rocks. This process called erosion (From Latin erosion - Erosion). Temporary streams water cut on the surface vymoyiny - Penetration of 1-2 m. If vymoyiny not fixed plant roots, after regular discharge of deepening and expanding. As a result vymoyiny converted on ravines. Yara grow after each rain. Over time, erosion is reduced. The slopes of the ravine becomes a flat. They grow herbs and shrubs. Then gradually turns into a ravine beamThat no more increases. Causes vymoyin and ravines of heavy rainfall and the presence of rocks that easily blurred. Rivers are extracted Devise a recess - River ValleyAnd blur shores. In addition, they carry and lay destroyed in the course material and estuary.

Groundwater dissolve some rocks such as limestone, chalk, gypsum, and salt. Consequently, under underground cavity formed - cave. Leaching and the making of groundwater causes subsidence loose rocks surface and the formation of depressions. Theyand resemble shallow saucer. In Ukraine, the basin is in forest-steppe and steppe because these landforms called steppe saucers.

Work Seas. Destructive techniques Sea provide shocks waves (surf) on shore. During the storm the shock wave strength strongest near the steep banks. Numerous breaking form in the bank Niche. Later part of the coast, which hangs over it collapses. The waves tossed by debris and bombard them emerging ledge, destroying it with greater force. Coast gradually recedes deeper into the land, and large debris crushed.

Simultaneously creative work is the sea. Sea waves carry debris and lay rocks, forming a band loose sediment - Beaches. They are sandy, shell, pebble. Sometimes the waves along the coast namyvayut narrow Spit. For example, in Ukraine Spit Arabatskaya arrow formed along the coast of the Azov Sea.


Fig. Water Work


Work glaciers. The activity of the glaciers that covered mountains and polar regions, similar to the work surface water. Spovzayuchy, glaciers grind Devise and surface depressions. When sailing in Glacier vmerzayut different fragments rocks, which are moving with it. When the edge of the glacier melts, all that he brought postponed. These deposits are called Moreno.

Employment Rights. Activity more tangible human impacts on the Earth's surface. With powerful Technology people have learned to alter the natural surface of the planet, adapting its for their needs. As the forces of nature, they destroy the surface when extracted minerals rozoryuyut farmland, construct different buildings and paths. Man creates on the surface of man-made (unnatural) form - holes-career, Increase as embankments etc..   

External processes are continuously and simultaneously with internal. As a result of this interaction surface of the Earth becomes complex appearance and constantly changing.


FAQ task

1. What are the effects ascribed to external processes?

2. What is called aeration and what are its types?

3. What are the effects of wind and where they can see?

4. What work carried out surface and which - groundwater?

5. What and how to create and destroy the waves of the sea?

6. What is the impact on the surface of glaciers?

7. What kind of surface is called artificial?




Stately mountains and vast plains, tall cones of volcanoes and deep valleys mizhhirni, sand hills and ravines make the Earth's surface is extremely uneven. Forms inequalities mainland and oceanic crust are very different. They are distinguished by shape, size, origin, and age. Are convex (hills, mountains), concave (ravines, valley, depression), flat and hilly. A set of land surface roughness called relief. Diverse relief - a result of the interaction of internal processes that create inequality and outside who are trying to level them. If we imagine the Earth without ocean water, we see the greatest inequality crust: ocean basin and continentsThat rise above them. They define the "face" planet so called planetary topography. And on the mainland, and ocean floor topography is the main plainand mountains. They are less complicated forms - hills and valleys, hills and ravines, and furrows bush and others.


Fig. Landform