What such is soil?

Soil - thin upper layer of the earth's crust, which gives life to plants. These are independent the natural body, which is something is average between the living and dead substance. In the soil interact the lithosphere, the atmosphere, hydrosphere and biosphere, and the density of the living substance of planet is maximum.Most valuable property of soil - fertility, i.e., the ability to ensure plants with the necessary nutrients and moisture.

Soil consists of mineral particles, organic matter in essence of plant origin, ground water, soil air and its populating living organisms. In different regions of the Earth the thickness of soil varies from several centimeters to 2-3 meters. Soil is formed very slowly, for the complete renovation of its mineral part at the depth 1 m it is necessary of 10 000 years.The founder of the contemporary pedologyconsidered that, it is similar to minerals, plants and animals, soils are special natural history bodies. They are formed under the effect of several factors of soil formation, which act simultaneously.The rocks, on which are formed the soils, are called maternal or soil-forming, they serve as the source of the mineral part of the soil and is determined its chemical, mineral and mechanical composition.On climate depend the thermal and hydrological conditions of soil formation, and also the speed of the weathering of the rocks. Vegetation supplies the soil organic matter and it noticeably influences its microclimate.Animals the microorganisms, which populate soil, intermix and loosen it, and they also accelerate the decomposition of organic remainders.

Depending on relief are redistributed heat- and moisture, and chemical composition and regime of ground and ground water act on many soil processes.On the forming of soil economic human activity has an enormous effect: it cultivates the earth, and in order to obtain a good harvest, it introduces into the soil of fertilizer.The formation of soil begins from the weathering - destruction and crushing of the rocks. At the friable mass appear the first bacteria, fungi and algae. In the process of their vital activity is formed the thin film of organic matter, on which first settle the lowest plants - mosses and lichens. The dying off plants and the remains of animals process microorganisms, organic

The permafrost

In the soil are formed the humus, the layer of black color, which is called humus. It contains the basic nutrients, necessary for plants. The greater the humus in the soil, the more fertile it is.As a result the prolonged processes of soil formation occurs the separation of soil thickness into the horizons - the uniform layers, which possess identical color, by structure, by structure and by other signs. For example, in the podsol soils of the mixed scaffolding of temperate zone from top to bottom usually is separated 1 horizon, in which occurs the accumulation of organic matter and the formation of humus; horizon 2 - washing out from which with the sufficiency of sediments occurs the extension of the part of the organic and mineral compounds; the horizon in , where the relatively mobile products of soil formation from the upper levels are accumulated; the horizon - the soil-forming species.By the degree of the manifestation of the separate soil horizons, their power, the chemical composition determine the types of soils - chernozems, podsol soils, solonchaks so forth

Under the conditions of cold climate the water, which is found in the depths and on the surface, freezes through at the depth to 500 m and more. More than 25% surface of the entire land of the Earth are occupied with permafrost species. In our country it is more than 60% such territory, indeed at the zone of its propagation lies almost entire Siberia.This phenomenon was called long-standing, or permafrost. However, climate in the course of time can change to the side of warming up, so that term “long-standing” more is suitable for this phenomenon.

The summer seasons

And they here very brief and transient - the upper layer of surface ground can thaw in the summer seasons. However, below 4 m is located the layer, which thaws never. Ground water can be located either under this frozen layer or remain in the liquid state between the permafrost thicknesses (it are formed water lenses - thawed reaches) or above the frozen layer. The upper layer, which is subjected to freezing and thawing, is called active layer.

POLYGONAL GROUND

Ice in ground can form icy veins. Frequently they appear in the places of the [ (resultant with the strong frost) cracks, filled with water. Ground between the cracks begins to squeeze with the freezing of this water, indeed ice occupies large area, than water. Is formed slightly the convex surface, by reductions. Such polygonal ground cover the substantial part of the surface of tundra. When brief summer begins and icy veins begin to thaw, are formed the entire spaces, similar to the lattice from the pieces of land, by aqueous “channels”. Among the polygonal formations rock polygons and rock rings are widespread. With repeated freezing and thawing of the earth occur the freezing, ejection by ice to the surface of the more coarse fragments, which are contained in ground. The sorting of ground in this way occurs, since its small particles remain in the center of rings and polygons, and coarse fragments displace to their edges. As a result appear the shafts of stones, which frame smaller material.

The mosses sometimes settle on it, and in autumn rock polygons strike with the unexpected beauty: bright mosses, sometimes with the bushes of cloudberry or the mountain cranberries, from all sides by gray stones, are similar to the specially made garden flower beds. In the diameter such polygons can reach 1 - 2 m. if surface not flat, but inclined, then polygons are converted into the rock strips. Freezing from ground of fragments leads to the fact that on the apical surfaces and the slopes of mountains and hills in the zone of tundra appears the chaotic piling up of the large stones, which are flowed together into the rock “seas” and “the rivers”. For them there is a name .

Nature of the Arctic

By this Yakut word is designated the surprising form of relief - hill or mound with the ice nuclei inside. It is formed because of an increase of the volume of water with the freezing in the suprapermafrost layer. As a result ice raises the surface thickness of tundra and appears mound. Large (in Alaska of them they call eskimo word can reach to 30-50 m of height.

In the high north latitudes (this of territory and the water areas, which lie to the north from 65- y of parallel) are located the natural zone of Arctic deserts, the zone of eternal frost. The boundaries of this zone as the border of the Arctic, are sufficiently conditional. Although the space around the north pole does not have a land, its role here satisfy continuous and floating ices. In the high latitudes there are islands, the archipelagoes, washed by waters of Arctic Ocean, within their limits lie and the coastal zones of continents Eurasia and North America.

These pieces of land almost wholly or in larger their part are forged “eternal ices”, or more precisely, remainders of the enormous glaciers, which covered this part of the planet during the last glacial period. The Arctic glaciers of archipelagoes sometimes exceed the limits of land and get down in the sea as, for example, some glaciers Spitsbergen and the Earth Franz Joseph.

The climate

The climate of Arctic deserts is extremely severe, with the high winds, with small amount of precipitation, by very low temperatures (the mean temperature even of the warmest month it is close to 0 °[S]). Snow cover is on dry land held almost the year round, descending only for the month -one-and-a-half. The long polar days and the nights, which are lasted on five months, short interseasons give special coloring to these severe places. Only the North Atlantic current introduce into some regions, such, as the West Banks of Spitsbergen, additional heat- and moisture.

Where all is covered with ice, life is it seems impossible. But this entirely not thus. In the places, where from under ice to the surface leave cliff- nunataks, there is its own plant world. In the cracks of the cliffs, where is accumulated a small quantity of ground, in the thawed sections of glacial deposits - moraines, near the snow fields settle the mosses, lichens, some forms of algae and even cereals and flowering plants. Among them [myatlik], cotton grass, polar poppy, [kuropatochya] grass- dryad, sedge, dwarfish willows, small birch, the different types of stone breaks. In the cold polar summer they manage to bloom and even to give fruits. The shelter finds on the coastal cliffs and nest in summer the numerous birds, that arrange on the cliffs “bird markets”, geese, seagulls, eiders, , snipe.

Dwell in the Arctic and the numerous Pinnipedia - seals, seal, walruses, marine elephants. Seals feed by fish, swimming in its searches to ices of Arctic Ocean. To be moved in the water with the enormous speed them the elongated streamlined shape of body helps. Seals themselves yellowish-gray, with the dark specks, and their young possess beautiful snowy , which they preserve to. Because of it they were called fur seals. Best-known inhabitant of the Arctic - polar bear. This is the largest predator on the Earth. The length of its body can reach 3 m, and the weight of adult bear of approximately 600 kgf and even is more!

The glacial period

The Arctic - reign of the polar bear, where he feels itself in its element. The absence of land does not confuse bear, in essence its locality - ice floe of Arctic Ocean. Bears - outstanding swimmers and in search of the food they frequently swim in far to the open sea. Polar bear feeds by fish, it hunts the seal, the seals, the young of walruses. In spite of its power, polar bear needs protection, it is carried into the red of international, and Russian.

Long-standing ice accretions in the high mountain regions and the cold belts of the Earth are called glaciers. All natural ices are united into so-called - part of the hydrosphere, which is found in the solid state. Into it enter ices of cold oceans, and icy caps of mountains, and separated from the glacial panels icebergs icebergs. In the mountains the glaciers are formed from the snow. First, during the recrystallization of the snow as a result of the alternation of meltings and new freezings of water inside the snowy thickness, is formed neve. which then is converted in the glacial under the action of gravitational force ice it is moved in the form icy flows. The basic condition for existence of glaciers - and small and enormous - constant low temperatures during the larger part of the year, with which the accumulation of snow predominates above its melting. Such conditions exist in cold regions of our planet - to Arctic and Antarctic, and also in the high mountain regions.

The ocean

GLACIAL PERIODS IN THE HISTORY OF THE EARTH. In the history of the Earth several times the strong temperature drop of climate led to the growth of glaciers and the formation of one or several glacial covers. This time is called or glacial periods.

In Pleistocene (epoch of the quaternary period of Cenozoic era) the area, covered with glaciers, exceeded contemporary almost triply. At this time in the mountains and in the plains of the polar and temperate latitudes arose the enormous glacial panels, which, increasing, covered enormous territories in the temperate latitudes. To represent, as the Earth in that period appeared, is possible, after looking in Antarctica or Greenland.

How they do learn about those old glacial times? Moving over the surface, glacier leaves its tracks - material, which took with itself during the motion. This material is called moraine. The stages of their standing note glaciers by the shafts of final moraine. Frequently on the name of the place, which reached the glacier, is called . Further entire glacier in the territory of East Europe it reached the valley of the Dnepr, and this is named Dneprovsk. In the territory of North America the tracks of the maximum advances of glaciers to the south relate to two ice formations: in the state of Kansas ice formation) and Illinois ice formation). Last ice formation reached the state of Wisconsin in the Wisconsin glacial epoch.The climate of the Earth strongly changed into the quaternary, or the Quaternary period, the period, which was begun of 1,8 million years ago and continuing to this day. How is caused this immense temperature drop - question, which the scientists solve.

Tens of hypotheses attempt to explain the appearance of enormous glaciers by many terrestrial and space reasons - by drop in the gigantic meteorites, by catastrophic volcanic eruptions, by changes of the direction of flows in the ocean.