Glaciers and rivers
Eternal throwing snow in the mountains, accumulating from year to year in comfortable hollows, circuses and on gentle slopes, acquires a granular structure and turns into firn. As the firn gradually thickens, it transforms into crystalline ice. When a lot of firn and ice accumulates in the depressions, it begins to "flow out" from them and, under the influence of gravity, slowly slides down the slope in the form of ice streams - glaciers. The largest glaciers descend to the bottom of the valleys and fill their upper reaches. Such glaciers are called valley glaciers. But many glaciers end on the slopes or do not come out of the depressions at all. These are hanging and tar glaciers.
The only current continental cap glaciers are those that encompass Greenland and Antarctica, their combined regions accounting for nearly ten percent of the earth's surface area. The Greenland polar cap covers 1.7 million square kilometers, or about 80 percent of the island. The Antarctic ice cap is nearly 14 million square kilometers.
Collapse of the Antarctic polar caps. In studies that used the latest satellite imagery, it is shown that parts of the glacial glacial platforms are separating. The event sent thousands of icebergs into the adjacent Weddell Sea. In total, about 250 square kilometers of the glacial platform were divided. This was not an isolated event, but part of a trend.
The area of modern glaciation in the mountains depends on the height of the snow or firn line - the lower boundary of the zone of eternal snow and glaciers, above which snow never melts.
Each glacier is divided by a firn line into two parts: an upper, or firn basin, where firn and ice accumulate (this is the so-called glacier recharge area) and a lower, or glacial tongue, descending from the firn basin down the valley and representing an area of melting or ablation glacier.
Why did these floating ice masses separate? Could there be serious consequences? Scientists have linked the separation of the polar ice caps to strong regional warming. If temperatures continue to rise, the glacier platform adjacent to Larsen B may begin to recede in the coming. In addition, regional warming of just a few degrees may be enough to cause parts of the huge Ross Glacier platform to destabilize and begin to split.
What will be the consequences? While the separation of the polar ice caps from the peninsula has little effect on sea level rise, the separation of other Antarctic platforms may have a large impact on the rate at which ice is separating from the continent. In addition, the caps keep the hottest sea air from glaciers; thus reducing the amount of melting that occurs on glacial surfaces. Adding a lot glacial ice to the ocean could, in fact, cause a significant rise in sea levels.
Often on the surface of the glacier, one can see cracks of various sizes and shapes, formed as a result of the movement of the glacier. The faster the glacier moves, the more cracks there are. Depending on the location and strike, the cracks are divided into longitudinal, transverse and diagonal, or marginal. Sometimes cracks also occur on the surface of firn fields, along their edges, at the foot of steep slopes - then they are called bergschrunds. Deep and snow-masked cracks pose a great danger to people passing along the glacier. There are especially many cracks in the places where the glacial bed falls, where the glacier is dissected by them into many ice sheets, teeth, spiers, so-called seracs, which form difficult icefalls. On gentle sections of the glacier, the melting of stones from the ice leads to the formation of peculiar forms of glacial relief: glacial tables, glasses, wells, ant heaps, etc. The glacier, when moving down, gradually abrades its bed and plows out a trough-like valley - the so-called trough with steep slopes and wide flat bottom covered with moraine sediments.
Recall that the proposed here is still an assumption, since our knowledge of the kelp of the polar caps and the glaciers of Antarctica is incomplete. Further satellite controls and further research in this area will be required to more accurately predict the possible increase in global sea level caused by the mechanism described here.
Often polar ice caps and ice cap glaciers feed glacier overflow. These icy tongues flow down the valley and extend outward from the edges of these larger ice masses. Tongues are essentially valley glaciers that are produced by the movement of ice from the polar cap or cap glacier through Terrenomontanoso to the sea. When they find the sea, some of the overflowing glaciers expand like glacial floating platforms. Many icebergs are produced frequently.
In destructive work, the glacier is helped by those debris that constantly slide down from the surrounding slopes to its surface and form lateral, middle and surface moraines. Part of these debris freezes into the ice and with their help the glacier, like a plane, abrades and grinds the bed and sides of its valley.
Moraines, covering the surface of the glacier and frozen into its body, slowly creep along with it along the glacial valley. Blue ice carries with it small grains of sand, and small fragments of stone, and huge boulders, sometimes reaching several meters in diameter and many hundreds of tons of weight. Water cannot bear such boulders, and in this sense ice is a more powerful worker than water.
Piedmont glaciers occupy wide lowlands on steep mountain bases and are formed when one or more alpine glaciers emerge from the confined walls of mountain valleys. In this case, the advancing ice expands into a wide ice sheet. The size of the foothill glaciers varies greatly. Among the largest is the Malaspina Glacier, located along the southern coast of Alaska. It covers over a thousand square kilometers of flat coastal plain at the foot of the high San Elias mountain range.
Its collapse at the beginning. Piedmont glaciers arise when the glaciers of the valley leave mountain range and extend into wide lowlands, are no longer confined to the sides and expand to large lobes. The Malaspina Glacier is actually a complex glacier formed by the amalgamation of several glaciers in the valley; among them are the prominent glaciers that appear here - the Agassiz glacier and the Seward glacier. In general, the Malaspina Glacier is up to 65 kilometers wide and extends 45 kilometers from the mountain front almost to the sea.
Where the glacier finally stops, all this debris is discharged at its end and sides. This is how terminal and coastal moraines are formed - a kind of barrier over which it is not easy for unfamiliar people to climb the glacier.
In the Digoria mountains, the firn line is located at an average altitude of 3450 m, rising from 3400 m in its western part to 3500 m in its eastern part. In addition, in each individual mountain range the snow line lies slightly higher on the southern slopes than on the northern. Therefore, the largest glaciers are located on the northern slopes of the ridges. In the high-mountainous Digoria, there are more than 60 glaciers, with a total area of about 90 square meters. km.
This perspective view to the north is approximately 55 kilometers x 55 kilometers. These images are great tools for comparing the geographic extent of glaciers and determining if those glaciers are depleting or thickening. What happens if the ice melts?
How much water is stored in glacier ice? But even 2 percent of a huge amount is a lot. The estimated total volume of the glaciers in the valley alone is 000 cubic kilometers, which is comparable to the combination of the world's largest marine and freshwater lakes. As for the cedar glaciers, Antarctica is made up of 80 percent of the world's ice and almost two-thirds of the Earth's fresh water and covers almost 1.5 times the area of the United States. If this ice melted, the sea level would rise by 0 - 70 meters, and the ocean would cover many densely populated coastal areas.
The largest number of glaciers is located on the northern, more gentle slopes of the ridges, where numerous spurs form basins convenient for the accumulation of snow and ice.
The largest glaciation center in Digoria is the Karaug-Saudi mountain-glacial junction, located in its central part, in the upper reaches of the Karaugomdon and Aygamugidon rivers. This "knot" accounts for more than half of the entire area of the modern glaciation of Digoria - 52.3 square meters. km, with a total number of glaciers 32. Here, at the intersection of the Main Dividing Range with its northern spurs, are the largest valley glaciers of Digoria - Karaugomsky, Songuti, Bartuy and Fastag.
The hydrological significance of Antarctic ice can be illustrated in another way. If the glacier cap melted at the same rate, it could feed the Mississippi River more than a thousand. All the rivers of the United States for about 000 years, the Amazon River for about 000 years, or all the rivers of the world for about 750 years.
Can glaciers form in tropical zones? Glaciers usually form where there is low temperatures and an adequate supply of snow. As temperatures drop as altitude increases, glaciers can be present at higher altitudes in the tropics. Even near the equator, glaciers can form at altitudes over a thousand meters. An example is Mount Kilimanjaro from Tanzania, located almost at the equator at an altitude of 895 meters. Climate change is causing the Kilimanjaro glaciers to shrink so that in 15 or 20 years the ice will completely disappear.
The Karaugom glacier, descending from the top of Bubiskhokh in the northwest direction, is the longest glacier in North Ossetia (13.3 km) and the second largest glacier in the Caucasus (26.6 sq. Km), after the Dykhsu glacier in Kabardino-Balkaria.
The second largest glacier in Digoria, Songuti, is located in the upper reaches of the Songutidon River (the main source of the Aygamugidon River). Its length is currently about 7 km, and its area is 8.2 square meters. km.
Batlan, Evolution of Herat, New York. Figure 5 Conversion of freshly fallen snow to crystalline and dense glacial ice. I, in the snow, is the raw material from which the glacial ice comes; As a result, glaciers form in areas where snow falls in winter. Before the glacier is created, the snow must become glacial ice. This transformation is shown in the figure.
When temperatures remain below freezing after a snowfall, the spongy accumulation of fine hexagonal crystals soon begins to change. As air enters the remaining gaps between the crystals, the ends of the crystals evaporate and water vapor condenses near its center. Thus, the snowflakes become smaller, thicker and more spherical, and large porous spaces disappear.
The first neighbor of Karaugom from the west is the Fastag glacier with a length of 3.5 km, followed by Bartui, the third largest glacier of Digoria, reaching 4.8 km in length.
To the west of the Songuti glacier lie in deep cirques the smaller glaciers - Skatikom, Kadurkhoshkhin and Huppara, giving rise to the Sardidon River - the left source of Aygamugidon. To the east of the Songuti glacier are the Kaysar and Donisar glaciers, which feed the right tributaries of the Songutidon - Kaysardon and Donisardon.
In this process, air is forced out and, which at one time was spongy and light snow, recrystallizes into a much denser mass of fine grains that have the consistency of thick sand. This granular recrystallized snow is called neviza and is commonly found on ancient snow shores at the end of winter. As the amount of snow increases, the pressure in the lower layers increases, thereby compacting the deep ice grains.
The weight of the ice and snow exceeds 50 meters, enough weight to melt the snow into a solid mass of ice crystals. Ice ice has just formed. Glaciers and Glaciers: Glacier Balance. The movement of glacial ice is often referred to as flow. The fact that glacial movement is described in this way seems paradoxical: how can a continuous stream?
Modern glaciation is also widely developed in the western part of the Main Watershed. Here, from the slopes of the Laboda and Gezetau massifs, two large valley glaciers descend towards the Khares Gorge - Tana, 3.5 km long and Mosot, 3.6 km long, giving rise to the right tributaries of the Khares River.
Between the Tana and Bartuy glaciers there are three small but very beautiful glaciers - Taymazi (Western and Eastern) and Gebi, often visited by climbers and tourists.
The way ice flows are complex and are basically of two types. The first of these, plastic flow, involves movement within the ice. Ice behaves like a brittle solid until the pressure on it is equal to the weight of about 50 meters of ice. When this load is exceeded, the ice is treated as a plastic material and begins to flow. This flow is due to the molecular structure of the ice.
Glacial ice is made up of layers of molecules packed on top of each other. The bonds between layers are weaker than within each layer. Therefore, when the force exceeds the strength of the bonds holding the layers together, they remain intact and slide on top of each other.
On the Sugan ridge, glaciers are concentrated mainly on its northern slopes, in the upper reaches of the Khaznidon, Bilyagidon, Psygansu rivers, where there are 12 glaciers with a total area of about 16 square meters. km. On the southern steep slope of the Sugan ridge, modern glaciation is much less developed. Small tar and hanging glaciers prevail here.
The second, and often no less important mechanism for the movement of glaciers is the movement of the entire mass of ice along the landscape. With the exception of some glaciers located in the polar regions, where ice is likely to freeze to bedrock, most glaciers are believed to go through this process called basal slip. In this process, the melt water likely acts as a hydraulic jack and possibly as a lubricant that helps the ice move on the rock. The origin of liquid water is partly due to the fact that the melting point of ice decreases as pressure increases.
The modern glaciation of Digoria, like the entire Caucasus as a whole, is only a small remnant - a relic of an ancient much more powerful glaciation that covered not only the mountains, but also the foothill plain 1 million years ago. And even quite recently, in the first half of the 19th century, glaciers descended along river valleys much lower than now, to absolute marks of 1600-1700 m.Then, as a result of climate warming, they began to rapidly retreat up the valleys and survived only in upper reaches.
In addition, other factors can contribute to the presence of melting water in deep regions of the glacier. The latter process depends on the property, according to which, when water changes from liquid to solid, heat is released. The influence of these two main types of glacier movement is shown in the figure. This vertical profile on the glacier also shows that not all ice is flowing forward at the same speed. Friction at the bottom of the rocky substrate causes the lower parts of the glacier to move much more slowly.
In contrast to the lower part of the glacier, the upper 50 meters, more or less, are not under sufficient pressure to exhibit plastic flow. When a glacier moves over uneven terrain, the crack zone is subject to tension, causing cracks called cracks. These gruesome crevasses can make glacier travel dangerous and can extend as deep as 50 meters. Below this depth, the plastic stream compresses them.
The retreat of glaciers continues to this day. During the period after their first survey (80-90s of the last century), many glaciers have reduced their size by almost half, some small crust glaciers have disappeared altogether, large ones have divided into less significant ones.
However, the rate of retreat of glaciers is not the same even in neighboring gorges or on different slopes of the same mountain-glacial massif. The glaciers of the southern and eastern slopes are retreating most rapidly, and the glaciers of the northern exposures are much slower.
In addition, the entire mass of ice can slide over the terrain. Ice in the fault zone is transported "in tow". Note that travel speeds are slowest at the base of the glacier, where thrust is greater. Is it possible? It is clear that people living in arid regions have seriously studied the possibility of towing icebergs from Antarctica to serve as a source of fresh water. Of course, there is a large supply. Every year, in the waters surrounding Antarctica, about 1,000 cubic kilometers of glacial ice breaks loose and creates icebergs.
However, there are significant technological problems that are unlikely to be resolved soon. For example, ships capable of towing large icebergs have not yet been developed. Also, there would be a significant loss. Ice melting and evaporation that occurs when an iceberg slowly crawls through the warm ocean waters.
Some glaciers, located in deep gorges and covered with powerful moraines, are in a stationary state, others, due to favorable nutritional conditions, even advance.
Observations of the most recent years indicate that since the 60s of the XX century, many glaciers have shown signs of stabilization, a decrease in the rate of retreat, and even a transition to the stage of ice advancing. At present, Digoria, as well as throughout the Caucasus, is dominated by small tar and hanging glaciers with a size of 0.8-1.0 square meters. km, there are only 18 large valley glaciers more than 2.0 km long.
Glaciers, conserving in themselves centuries-old reserves of moisture, then give it drop by drop to rivers, streams and groundwater.
Digoria is very rich in surface waters. All its numerous rivers and streams belong to the basin of one river - the Urukh - a large left tributary of the Terek River, which flows into it far on the foothill plain, outside North Ossetia, in Kabardino-Balkaria. The total length of the Urukh River is 105 km, of which the high-mountainous Digoria accounts for 27 km. Starting from under the glaciers of the Main Dividing and Su-Gansky ridges, this river in its upper reaches is called Khares and flows from southwest to northeast along the longitudinal Shtulu-Khares valley.
After the confluence with the Karaugomdon river (absolute height 1490 m), flowing out from under the Karaugom glacier, the river immediately becomes abundant (increasing in volume by 2.5-3 times) and turns steeply to the north. Hence it is called Urukh ( Locals this river is often called Iraf.)
Flowing further along the bottom of the wide Urukh gorge, the Urukh river receives its two largest tributaries: on the left - Bilyagidon, on the right - Aigamugidon. 4 km below the village of Matsuta, Urukh cuts into the dense light gray limestones of the Rocky Range, forming a narrow and deep Digorskaya gorge. The Urukh River reaches the plain near the village of Kalukh (absolute height 750 m).
The rivers of the high-mountainous Digoria feed mainly on melted snow and glacial waters, but they also receive a significant share of water from rain and groundwater... Therefore, their regime is distinguished by great inconstancy. Mountain rivers are most full-flowing in summer, in July-August, when glaciers melt most intensively. The water in them at this time is muddy and dirty. Boulders rolling along the bottom of the river collide with each other and produce an incessant rumble, which intensifies especially towards the end of the day and in the evening.
When there are heavy rainfalls in the mountains, the amount of water in the rivers increases many times and floods occur. Rivers overflow their banks, turning into powerful stormy streams, washing away everything in their path. An example is the flood of August 6, 1967, when all the rivers of the Terek basin overflowed their banks, destroying roads, bridges and settlements... The usual amount of water in the Urukh River - 27.4 m3 / sec - increased at that time in the alignment of the village of Akhsarisar by 2.5 times and reached 68.5 m3 / sec.
The water level changes noticeably in mountain rivers and during the day, it rises sharply in the afternoon. Therefore, it is necessary to cross these rivers in the morning, before the snow and glaciers begin to melt.
Mountain rivers look completely different in the cold half of the year. From muddy and noisy streams, in autumn and winter, they turn into small streams with transparent, like glass, bluish water streaming along their rocky bed.
Due to the fast current, the water in mountain rivers does not freeze in winter, and only during severe frosts do banks form on them, ice freezing along the banks.
Mountain glacial basin Aktru occupies the southeastern part of the Bish-Iirdu mountain cluster of the North-Chuisky ridge. The total area of the basin is 42 km 2, and the area of modern glaciation is about 16 km 2. Absolute heights, located within the mountain glacial basin, reach about 4000 m above sea level. m., and the top of Aktru-Bash, located in the northwestern part, rises to 4075 m. The boundaries of the basin pass along the high watershed ridges of the North Chuysky ridge and its spurs - the Peredovoy and Kashkalych ridge. The area of our study is located in the high-mountainous part of the basin; we consider only the upper reaches of the river. Aktru, bounded by a closing section at the end of the valley outwash, excluding the middle and lower course.
Quaternary glaciation had a great impact on the development of the forms of the modern relief of the basin, here there is a “fresh”, highly dissected alpine relief of the high-mountainous Altai, where the processes of physical weathering are especially intense, and the processes of relief formation are easily observed and compared with each other.
The relief of the Aktru glacier basin and its development
... The main features of the modern relief of the Aktru mountain glacial basin were formed as a result of prolonged water-glacial erosion, acting against the background of intense tectonic uplift of the Bish-Iirdu mountain cluster. The beginning of the formation of modern morphostructures in Altai is attributed by most researchers to the end of the Tertiary and the beginning of the Quaternary time (Nekhoroshev, 1958). The Bish-Iirdu ridge is characterized by undoubted youth, and the modern relief is the result of the dissection of the highly elevated surface, which began simultaneously with the uplift in the Quaternary. The uplift was characterized by the formation of a modern river network with a typical V-shaped relief [Dushkin, 1967].
During the period of the onset of glaciation, the dissected V-shaped relief was deepened and significantly reworked by glaciers against the background of intensive uplift. Apparently, the valley of the river. The actress experienced double glaciation [Ivanovsky, 1967]. During the period of the first glaciation, the main kars were formed in the basin at altitudes from 3000 m above sea level. The most pronounced in the relief are the forms formed during the last glaciation, which make it possible to establish the relative chronology of the events that took place in the valley [Ivanovskii, 1967]. Aktru, up to 2.5 m high. Judging by the woody vegetation that has settled on them, they are about 150-170 years old. Consequently, the amount of uplift in this area can be estimated at approximately 1–1.5 cm / year [Dushkin, 1967].
a brief description of geological structure
... In general, the mountain glacial basin is composed of uniform and highly dislocated sericite-chlorite schists with an admixture of quartzite and other rocks of the Devonian age. Devonian deposits are divided into two strata: effusive-sedimentary and sandy-shale. The effusive-sedimentary strata is represented by a complex of rocks: quartz porphyries, black and dark gray shales, gray and tobacco-yellow sandstones, limestones. The sandy-shale strata is represented by black and gray shales, finely interbedded with the same limestone and marly sandstones (Appendix 1). In addition to the Middle Devonian sediments, the Upper Silurian marine sediments of the Chuya formation are widespread in the valley, represented by green and green-gray sandstones, interbedded in places with green, lilac and gray-lilac clay shales [Petkevich, 1972].
Folds tectonic structures have a common northwest strike with steep dip angles - 70–80 °. Shales, sandstones, limestones are rocks that are subject to weathering rather quickly and give, when destroyed, a large amount of debris. The cracks in the shale propagate along the shale plane, and in the valley the weathered shale is slab-shaped. In sandstones, cracks penetrate deeper, therefore, when weathered, massive acute-angled fragments break off. The steep dip of the strata also contributes to the rapid weathering [Petkevich, 1972].
Fast-flowing (permafrost, nival-glacial and gravitational) processes are of the greatest importance in the formation of the modern relief of this territory. Their manifestation can be the slopes of the northern exposure with heights of more than 2700 m, where nival-glacial processes are dominant. Frequent rockfalls and avalanches lead to the accumulation of clastic material of various dimensions in the form of talus cones at the foot of steep slopes [Titova, Petkevich, 1964].
Morphometric characteristics
... One of the features in the morphometry of the mountain glacial basin of the river. Aktru is a well-expressed asymmetry of the slopes, where the northern slopes are steeper (55–60º), and the southern ones, on the contrary, are more gentle (47–49º). This asymmetry of the valley sides determined the development and preservation of glaciation in past eras, when the heated southern slopes were more exposed to physical weathering than the northern ones, which more evenly fell under the “protection” of snow-firn masses. Subsequently, with the degradation of glaciation, the more illuminated slopes of the southern exposure quickly freed themselves from snow, and the processes of nivation resumed their destructive effect. In places of intensive development of talus, the relative height of the sides of the river valley. Aktru reaches 1200 - 1400 m, a large number of snowfields are observed here, and their melting contributes to significant moisture on the right slope. The asymmetry of the valley sides also determines the characteristics of the arrival of solar heat to the surface of the slopes and, as a result, the parameters of thawing of the soil of the valley slopes. As a result, the characteristics of the rate of denudation processes on slopes of different exposure will differ.
Climatic features
... The highland climate, determined by the height of the territory, as well as by the direction of the ridges and the exposure of the slopes of the mountain valleys, can be characterized as alpine nival with long (November-March), albeit relatively mild winters, short (June-August) cool summers and short, mild transitional seasons.
The climatic indicators obtained as a result of observations in the Aktru mountain glacial basin can be considered, according to M.V. Tronov, “by some means for Mountain Altai”[Tronov, 1973].
The absolute minimum was recorded in December - minus 34.1 ° C, the maximum in July was 24.3 ° C. The main meteorological process summer season consider the radiation transformation of warming, and the main process of the winter season is winter cooling. Therefore, the average temperature in June is 8.2 ° C, in July - 9.9 ° C, in August - 8.1 ° C. average temperature winter months: November minus 14 ° C, December minus 18.4 ° C, January minus 19.5 ° C, February minus 14.9 ° C, March minus 11.7 ° C. Average daily amplitude of air temperature is 10.5 ° C. Large daily amplitudes of air temperatures are observed in clear weather and are associated with strong daytime warming, and not with nighttime cooling. Temperatures rise rapidly in clear weather. In one hour, the temperature can rise by 4-5 ° C (on August 10, 1957, from 7 to 9 o'clock, the temperature rose by 9 ° C) [Petkevich, Titova, 1962].
The maximum air temperature gradients are observed near earth surface decreasing with distance from it. The maximum difference between the soil surface temperature and air temperature at a height of 0.5 m reaches 13.3 °, and in the 0.5–2 m layer the gradient does not exceed 0.13 deg / m. In clear weather, the average vertical gradient of air temperature in the Aktru valley to an altitude of 3000–3100 m (the level of the snow boundary) is 0.9 °, in cloudy weather it is normal - 0.5 ° per 100 m [Sevastyanov, Dyachkova, 1981].
In the highlands, frosts are practically possible throughout the year. So, for the observation period from 1957 to 1966. at Aktru station, the following number of cases of temperature transition on the soil surface through 0 ° was noted: June - 7, July - 2, August - 4, in September it already increases to 18, and in April to 19, in May to 16 [Observation materials ... , 1980, 1987]. The transition of temperatures through zero degrees determines the frequency of the freezing-thawing process of water in cracks and pores of rocks, and therefore, in some way, the effectiveness of frost weathering, since the transition of free water to ice is accompanied by an increase in its volume by 9-10% and an increase in pressure up to 2100 kg / cm 3.
The course of temperatures on the soil surface, as mentioned above, is determined by the intensity of radiation. The arrival of solar radiation on the day surface of landslide-accumulative slopes reaches in the valley of the river. Actru 1-1.3 cal / cm 2 per minute. (or 4.1868–5.4428 J / cm 2 per min.). Total solar radiation is 99.26 kcal / cm 2 per year (or 415.58 kJ / cm 2 per year) [Sevastyanov, 1998]. However, the general obstruction of the horizon in the valleys significantly reduces insolation [Titova, Petkevich, 1964]. In addition, it decreases due to high cloudiness during precipitation. Therefore, high mountains are characterized by an alternation of days with large and small amounts of radiation, and, consequently, days with high and low temperatures, which cannot but affect the processes of destruction and demolition of rocks.
The Aktru mountain glacier basin is characterized by a significant annual amount of precipitation - from 700 to 1000 mm; 70% falls in the warm season - from April to October, determining the moisture of the rocks. In mountain valleys, precipitation, as a rule, falls in liquid form in summer, however, at altitudes of more than 2200 m, snowfalls are possible in summer. A stable snow cover lays down in early September and lasts for about 7 months, reaching a height of 100 cm or more. Snow patches (“snowfields”), which persist in the summer on the slopes of the valleys, are a significant geomorphological factor.
The highlands are characterized by complex air circulation associated with vortex movements along steep and high slopes. On the peaks, there is an almost unchanged circulation of the free atmosphere, and in the mountain valleys, mountain-valley winds, complicated by phenes, prevail. Calm weather accounts for 10% of the total number of observations. Observations show that on slopes wind speeds increase with height. Gusty winds with frequent changes of direction prevail there [Sevastyanov, 2008].
Conditions of physical weathering of rocks in Aktru
... As it was found [Shmygleva, 1978], the amplitude of the diurnal temperature variation on the surface of the rocky slope is high, and it mainly depends on warming up during the day. The daily temperature range on the southern slopes is 10–15 ° C, on some days it can reach 35–40 ° C. Temperature fluctuations attenuate at a depth of 30–50 cm. In winter, material is supplied to the foot of the slopes mainly due to avalanche drift.
The main factors of weathering in the Aktru mountain glacier basin are temperature fluctuations (temperature weathering) and frost weathering, which occurs as a result of the expansion of water that repeatedly freezes and thaws in cracks and pores of rocks. Therefore, the rate of weathering is proportional to the sum of the daily temperature amplitudes and the number of its transitions through the freezing point of water. Strong fracturing and sufficient moisture saturation of rocks, as well as location in close proximity to glaciers - all this favors the development of forms of accumulation at the foot of the slopes. The largest fragments of shale quickly disintegrate into smaller ones and, under the influence of gravity and the transporting ability of water, are carried down the slope. In sandstones, cracks penetrate deeper, therefore, when weathered, massive acute-angled fragments break off. The steep dip of the strata also promotes rapid weathering.
The rate of weathering of rocks within the upper reaches of the mountain glacial basin of the river. Aktru, according to M.A. Dushkin, is 6–8 mm / year [Dushkin, 1964], moreover, frost weathering prevails with the rise in altitude, and temperature weathering prevails in lower areas.
The typicality of the complex of oro-hydro-glacial-climatic characteristics of the river basin. Aktru makes it possible to consider the basin as representative for the entire high-mountainous Altai [Tronov, 1973].
Based on the foregoing, the entire territory of the Aktru mountain glacier basin can be conditionally divided into three zones with a certain set of elements characteristic of this area. These are zones: glacial, periglacial and non-glacial.
Glacial zone
... Covers the area of distribution of modern glaciation; here the main factor in the transformation of the relief is the activity of glaciers and frost weathering. Average heights are 3000-3500 m above sea level. m. In this zone, there is an active formation of modern moraines and young accumulative formations at the foot of the slopes. The demolition of rocks occurs mainly due to the subsidence of boulders, their collapse on steep walls and slopes with a steepness of more than 42–45 °. And the transportation of clastic material is carried out due to the movement of glaciers and under the influence of temporary streams that arise when a large number of snowfields melt on the slopes. Glacial gouging of the valley sides is also characteristic of this zone.
Perglacial zone
... It is located below the terminal fields of glaciers and is confined mainly to the places of distribution of moraine accumulations and to the slopes of predominantly southern exposures. Average heights are in the range from the forest border (2200 m) to 2800 m above sea level. m. On the slopes, the dominant processes are crumbling, shattering of debris due to temperature weathering. On flat watersheds, the movement of debris is carried out due to cryogenesis and solifluction. In this area, there is an active preparation of material for demolition under the influence of the above processes. Accumulative formations are developed at the foot of the slopes. In winter, avalanches from the slopes are quite frequent.
Off-glacial zone
... It is located from the confluence of the Small Aktru and Bolshoi Aktru water streams to the closing section located at the bottom of the valley at an altitude of about 2000 m. Aktru outside the territory under consideration. Also in this area, solifluction processes, landslides and mudflows have developed. On steep slopes in winter, with sufficient snow accumulation, avalanches may occur.
Thus, in the Aktru geomorphosis, the following can be distinguished structural elements: landslide-accumulative slopes; slopes with developed landslide processes; glacial systems; river floodplain system Actru, as well as non-structural processes such as cryogenesis and earthquakes, which are involved mainly in the form of agents for the preparation of the material and / or its movement.
Literature
1. Dushkin M.A. Formation of modern moraines on the terminal field of the Big Aktru glacier // Glaciology of Altai. Tomsk: publishing house of Tomsk University, 1964. 3. - S. 101-114.
2. Dushkin M.A. Geomorphological outline of the Aktru glacial basin // Glaciology of Altai. - Tomsk: publishing house of Tomsk University, 1967. issue 5. - P 42–65
3. Ivanovsky L.N. Forms of glacial relief and their paleogeographic significance in Altai. L .: Science, - 1967 - 263 p.
4. Nekhoroshev V.P. Geology of Altai. - M .: Gosgeoltekhizdat, 1958 .-- 262 p.
5. Petkevich M.V. On physical weathering in the highlands of Southeastern Altai // Glaciology of Altai. - Tomsk: publishing house of Tomsk un-that, 1972. - From 184–202
6. Sevastianov V.V., Dyachkova L.P. On the vertical gradient of air temperature in mountainous Altai in summer // Glaciology of Altai. - Tomsk: publishing house of Tomsk University, 1981. in. 7. - S. 73-77
7. Sevastyanov V.V. The climate of the high-mountainous regions of Altai and Sayan. - Tomsk: publishing house of Tomsk University, 1998. - 202 p.
8. Sevastyanov V.V. Ecological and climatic resources of Altai-Sayan mountainous country... - Tomsk: LLC "RauSh MbH", 2008. - 307 p.
9. Titova Z.A., Petkevich M.V. Observations over accumulation cones in the Aktru river valley // Glaciology of Altai. - Tomsk: publishing house of Tomsk University, 1964 c. 3, - pp. 115–143.
10. Tronov M.V. Aktru mountain glacial basin as an indicator of the characteristic properties of the oroclimatic base of glaciation // Problems of glaciology of Altai. - Tomsk: publishing house of Tomsk University, 1973. - From 7–20
11. Shmygleva G.M. some features of the meteorological regime of the rocky slope in the mountain glacial basin of the river. Aktru // Glaciology of Altai. Tomsk: publishing house of Tomsk University, 1978. 14. - S. 143-152.
