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Rocks and a relief

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All variety of terrestrial landscapes was generated under the influence of three major factors: hardness of the rocks making a surface of a land, their structure and the forces of the nature constantly changing outlines of a surface.

The Relative fortress (hardness) of rocks is their ability to resist to mechanical destruction. Many magmatic and metamorficheskie breeds possess high hardness as consist of crystals. For example, such crystal magmatic breed as the granite, often lies down on a surface in mountain areas thanks to resistibility to erosion. The granite was formed of the fused magma which cooled down and have hardened in bowels of the Earth, and bared as a result of aeration of more friable breeds which were lying down over it.

Volcanic breeds, including the fallen asleep lava and ashes, usually collapse much faster a granite. Often from an extinct volcano remains only it nekk - some kind of a pipe on which magma left on a surface.

Sedimentary breeds also happen different hardness. So, the breeds formed from glin, are unstable and are quickly washed off. Therefore they often form valleys between the bared sandstones and limestones. Crystal, or mountain, limestones resist to erosion and often form abrupt rocks. This kind of limestone covers spreading friable breeds at Niagara Falls in the North America. A chalk, it is weak kristallizovannyj a limestone kind, is less steady. Therefore cretaceous hills usually happen flat.


Structure of rocks

The Relief depends and on structure of rocks. When the fallen asleep lava turns to basalt, it is often compressed in shestigrannye columns. In cracks between them breed is opened to destroying action of a rain, ice and water streams.

Rain water transforms in due course vertical cracks Arising in mountain limestones into deep wells. A surface water flows down in these karstic funnels, or ponory, washing away a network of underground caves. Such kind of a landscape is called as karstic - under the name of area of limestones in Yugoslavia.

Earth movements destroy breed, creating breaks, or dumps along which they move, causing earthquakes. Sometimes blocks are squeezed out upward, forming abrupt slopes - waste ledges.

Structure of rocks Or the earth crust block can settle between two almost parallel dumps. So the valley limited to two abrupt waste ledges is formed riftovaja. When breed layers settle down naklonno as a result of earth crust shift, firmer breeds form ridges - kuesty, - and less steady disappear and form between them valleys. At small shift of a layer of breed one party kuesty usually forms an abrupt steep slope, and another - flat. Typical examples of such landscape are Kotsuolds-Hils and Chiltern Hills, hills in the south of England.

Other characteristic kinds of a landscape form the layers of breeds crumpled in folds. For example, Uild in the southeast of England represents an anticline (a fold turned by camber upwards). The anticline top has disappeared.


Forces of the nature

Some landscapes are obliged by the formation to not so much spreading breeds and structures, how many external destroying influence of forces of the nature. So, many mountain areas were generated under the influence of a frost and glaciers (ice streams). To these forces many characteristic kinds of a relief, including U-shaped valleys (trough valleys), kresloobraznye pools (penalties) and pyramidal peaks (karlingi) are obliged by the occurrence.


As rocks

are formed

Three principal views of rocks - magmatic, sedimentary and metamorficheskie - were formed differently.

As rocks Magmatic breeds are formed formed of magma (the fused weight of an internal cloak of the Earth) as a result of its cooling and hardening. Sometimes magma is superseded on a surface and streams from craters of volcanoes in the form of a lava. Basalt - one of ekstruzivnyh the rocks named so as magma cools down and hardens on a surface of the Earth. Intruzivnye breeds are formed at magma hardening in earth crust. Most often from such breeds the granite is meeting. Sedimentary breeds consist of splinters erodirovannoj breeds, and sometimes from the rests there is live matter. Breed splinters, including a pebble, sand and clay, are transferred by a wind or water streams or glaciers and usually settle at the bottom of lakes and the seas where are gradually condensed. Filtering through the condensed particles, water leaves there minerals cementing them. Here conglomerates (stsementirovannyj galechnik with an impurity of more thin material), sandstones (consisting of sand particles), and also clay slates, or argillit concern. Some kinds of limestone were formed of the rests of the died out organisms, such as a shell rock. The straight limestone (chalk) consists of the plankton rests (microscopic sea plants and animals). Coal concerns the breeds consisting of the hardened rests of a vegetative material. Other sedimentary breeds were formed of the chemical substances dissolved in water. So there were separate kinds of limestone, and also the stone salt formed at evaporation of sea water.

To metamorficheskim the magmatic or sedimentary breeds changed as a result of heating, pressure or chemical reactions concern. So limestone becomes marble, and the condensed clay - slate.