What are Glaciers?

Natural ice bodies that exist on the surface of polar or alpine regions for many years and have movement along the ground. The glaciers are covered with snow for many years and formed through compaction, recrystallization, and freezing. It has a certain shape and layer, and has plasticity. Under gravity and pressure, it produces plastic flow and block sliding. It is an important fresh water resource on the surface. The International Glacier Catalogue stipulates that all perennial snowdrifts and ice bodies with an area of more than 0.1 square kilometers should be included in the Glacier Catalog ^[1]

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2019-03-18 23:03 Chinese glacier history2019-03-18 23:03

For most people, glaciers are familiar but strange. It is familiar that some glaciers are within reach. Like the Hailuogou Glacier under the Gongga Mountain, tourists come all year round to appreciate its stunning beauty. However, the vast majority of glaciers in China are distributed in the extreme mountains of the west, where they are covered by snow and ice, lack of oxygen and high temperatures, and few people travel. We don't know much about its appearance, and we are even more unfamiliar with its scientific value. ... more

Glacier formation

Glaciers are a form of existence of water, and snow is transformed through a series of changes. To form a glacier, there must first be a certain amount of solid precipitation.

Including snow, fog, hail and so on. Without enough solid precipitation as "raw materials", it is equivalent to "rice-free cooking", and there is no glacier at all.

In high mountains, glaciers can develop. In addition to requiring a certain altitude, it is also required that the mountains are not too steep. If the mountain peak is too steep, the falling snow will go down the slope, and no snow will form, so it will not be a glacier. Snowflakes will change as soon as they fall to the ground. With the change of external conditions and time, snowflakes will become spherical snow that completely loses its crystal characteristics. This snow is called grain snow.

After the snow turns into grain snow, as time goes by, the hardness of the grain snow and the tightness between them continue to increase. The big and small grain snow squeeze each other and are inlaid tightly, and the pores between them are continuously shrinking. It disappeared, the brightness and transparency of the snow layer gradually weakened, and some air was also enclosed inside, thus forming glacial ice. The process of granulation and densification progresses quickly at temperatures close to the melting point, and slowly at negative low temperatures. Glacier ice was milky white when it was first formed. After a long period of time, the glacial ice became denser and harder, and the air bubbles inside it gradually decreased, gradually turning into a crystal clear, old glacier ice with blue crystals. ^[2]

Classification of glaciers

World Glacier Distribution

Glaciers are mainly distributed in the poles of the earth and in high and low latitude mountain areas. The global glaciers cover more than 16 million square kilometers, accounting for about 11% of the total land area of the earth. Glaciers in the polar regions cover almost the entire polar region. They are called continental glaciers and ice cap glaciers. The glacier in the middle and low latitudes is called mountain glacier, also called alpine glacier. 97% of glaciers on earth and 99% of ice

Glacier map of China % Distributed in the Antarctic and Greenland ice sheets. The mountain glaciers are the most developed in the mountains of central Asia. The Karakoram Mountains cover 37% of the area. They are covered by 6 glaciers in Kashmir, each of which is over 50 kilometers in length. China's glaciers are all mountain glaciers. It was during the glacial age when the Quaternary glaciers were most prosperous that the scale of the glaciers greatly expanded and they did not develop into continental ice sheets. Many experts previously believed that the Qinghai-Tibet Plateau was covered by a large ice sheet during the Quaternary, even though some foreign experts still hold this view. However, after investigation and demonstration, glaciers in China have basically denied this view.

Glacial landform

Snow line: The position of the snow line in a place is not fixed. Seasonal changes can cause the snow line to rise and fall. This temporary phenomenon is called the seasonal snow line. Only the position of the snow line is relatively stable in summer, and it returns to a relatively fixed height every year. For this reason, the snow line height is measured in the hottest month of summer. Worldwide, the snow line decreases from the equator to the poles. The height of the snow line on the north slope of Mount Everest is about 6000 meters

Antarctic Peninsula Glacier Right, and in the north and south poles, the snow line drops below sea level. The snow line is an important symbol in glacial science, and it controls the development and distribution of glaciers. Only when the height of the mountain exceeds the snow line of the area, excess snow accumulates every year. Deep and long, it can become a region of permanent snow and glaciers.

Grain snow basin: the area above the snow line, snow falling from the sky and snow falling from the hillside are easy to gather in low-lying terrain. Because the low-lying terrain is generally shaped like a basin, it is called a snow basin in glaciology. The grain snow basin is the cradle of the glacier. How does the snow accumulated in the granulated snow basin become glacial ice? After a series of metamorphic effects, the snowflake gradually becomes granular granulated snow. There are many air channels between the grain snow, these air channels communicate with each other, so the layer of grain snow is loose like a sponge. In some places, the snow in the glacier granulated snow basin is very thick. The granulated snow at the bottom is slowly settled and compacted and recrystallized under the weight of the upper layer. The granulated snow is combined with each other to reduce the gap. At the same time, the surface melts into the water and partly freezes, which gradually closes the airway of the grain snow. The air enclosed in ice then becomes a bubble. This kind of ice contains a lot of bubbles and has a whitish color. Its bulk density is about 0.82 to 0.84 g / cm3, and it is also called grain snow ice. The grain snow ice is further compressed, and the air bubbles are discharged, turning into light blue glacier ice. The thick glacier ice plastically flows under the combined effect of its own pressure and gravity, and winds down the grain snow basin outlet, forming ice tongues of different lengths. Growing ice tongues can extend down to the valley and beyond the mouth of the valley. Mature glaciers generally have grain snow basins and ice tongues. The grain snow basins above the snow line are accumulation areas of glaciers, and the ice tongues below the snow line are melting areas of glaciers. The two are like the two ends of a balance, which together control the glacier's material balance and determine the glacier's activities. The snow line is exactly the fulcrum of the balance.

Glacier scene Ice bucket: In the valley near Shangyuan near the top of the mountain and the watershed, the terrain of a catchment funnel is always formed. When the climate became cold and glaciers began to develop, this type of water collecting funnel near the top of the mountain was first occupied by snow and ice. Ice and snow accumulate to a certain extent in the catchment funnel, and they flow into glaciers. The glacier has a great planing effect on the valley bottom and its edges. It continuously works like a carpenter's planer and file. The original collecting funnel is gradually shaved into a basin surrounded by mountains on three sides, like a rattan chair. This terrain is called an ice bucket. Most ice buckets develop at elevations near the snow line.

Generally, glaciers in valleys often climb up ice ridges to see the snow-covered granulated snow basins. When the glacier disappeared, the bottom of such a basin was an ice bucket lake. Bingdou Lake is often seen on high mountains, and they are regularly distributed at a certain height, which represents the height of the snow line in the ancient ice age.

Moraine: Water freezes into ice, and the volume increases by about 9%. When the melting ice and snow water freezes again in the rock cracks at night, it exerts a strong side pressure on the surrounding rock mass, and the pressure can reach up to 2 tons per square centimeter. Many rocks have cracked in the face of such strong frost heaves. Frost weathering occurs not only on bare hillsides, but also on glacial bottoms. This is because the glacier bed has temporary pressure melt water, which melts into the cracks in the rock at the bottom of the valley, and also generates a strong frost heave when it freezes. Frozen weathering constantly creates loose rock fragments on the slopes and glacial bottoms. Debris on the slopes roll down on the glaciers under the effect of gravity. Debris in the bottoms are more easily carried by glaciers. Flowing together. The gravel rocks of the glacier belt are commonly called moraine. The fragments of rock on the surface of the glacier are called surface ridges, the inside of the glacier is called the internal ridge, the bottom of the glacier is called the bottom ridge, and the side of the glacier is the side ridge. The side ridge is close to the hillside, and the source of gravel rocks is rich, so the side ridge is high and large, like the towering walls of the glacier sandwiched by the left and right. To the front of the tongue, most of the two side salamanders converge, forming a ring-shaped terminal salamander. The terminal block looks like a tall castle, guarding the glacier. Those who climb the glacier must first land on the terminal block to get close to the glacier. In the western part of China, many of them are over 200 meters high. Not all glaciers have a final glacier. There is no final glacier that moves forward and retreats quickly. Only when the glacier stops in a place for a long time can it cause a high final. When two glaciers converge, the two adjacent sides merge into a single center. The glaciers in the dendritic valleys are heavily sloppy, and the entire glacier appears in black and white stripes. Moraine is the main material carried and deposited by glaciers, and it is also one of the evidences that glaciers change the face of the earth.

Glacier annual rings: The grain snow and ice in the grain snow basin remain roughly flat, layer by layer. The ice layer accumulated every year is called annual layer in glacial science. After the winter snow melts in summer, an ablation surface is formed, and there is more dirt on the ablation surface, so it is also called the fouling surface. The stained surface is a natural sign for dividing the annual layer. With the annual layer, the ice layer can be measured like a tree wheel. Since the glacier formed some air and dust when it was formed, glaciologists can extract bubbles and dust from it to analyze the climate at that time.

Glacier views (20 photos)

Ice Lake: There are three main forms of ice lake. One is that the glaciers under the ice melt the glaciers, creating huge caves or tunnels, and the tops of the caves collapse, forming deeper and larger elongated lakes. One is due to the accumulation of water in the low depressions of the glacier, which is formed by strong ablation in summer. In addition, the horny peaks around the glacier are constantly falling down into debris. If larger rocks cover the glacier and cause differential ablation, they can grow into ice mushrooms of varying sizes. Ice cups form quickly, and large and small pools of water form on the ice surface. During summer ablation, the water temperature in the ice area is relatively high, sometimes reaching 5 ° C. Therefore, the erosion of the accumulated water is strong, which can gradually merge the honeycomb ice cups together to form a wide and shallow ice lake. The ice lake adds more colorful scenery to the glacier scenery. In summer, whenever the sun rises or the sun goes down, the sun on the lake is bright and dazzling.

Ice cave: In summer, glaciers are often in a state of ablation. Glacier ablation is divided into three types: sub-ice ablation, intra-ice ablation, and ice surface ablation. The crust often transports heat to the bottom of the glacier, causing it to melt under ice. But sub-ice ablation is trivial for huge glaciers. When melting water on the ice surface flows into the interior of the glacier along the cracks of the glacier, intra-ice melting will occur. As a result of melting within the ice, many unique glacial karst phenomena have been bred, such as ice funnels, ice wells, ice tunnels, and ice caves (we know that stone forests in Yunnan are formed by karst landforms. Like karst landforms, glaciologists call this glacier form a karst glacier).

Ice stalactite: the melting water on the glacier, in the flow process, often forms a small tree-like network of rivers, sometimes twists and turns, sometimes dive into the ice. On some glaciers with large areas of molten water, rivers in the ice are particularly developed. When rivers in the ice flow from the end of the ice tongue, they often erode into deep ice holes. The entrance looks like a low or high arch in the ancient city. The water flowing out of the ice cave, because it has suspended mud and sand, is as white as milk, and is called glacial milk in glacial science. When the glacier runs out, walking into the ice cave is like entering a crystal palace. Some glaciers, through tunnels in ice caves, can always go to the bottom of the glacier. Ice caves are single and branch-shaped, and there are holes in the caves. There are icicles in the cave, ice stalactites are hanging, and the pattern of the cave is very beautiful. Some ice cave exits hang high above ice cliffs, forming very spectacular ice water waterfalls.

Ice tower: Differential melting of ice surface produces many magnificent natural scenes, such as ice bridges, ice buds, ice walls and ice towers. Especially the ice tower forest has attracted many people's attention. Everest and icebergs are rare on many large glaciers in Mount Everest and Shishabangma. The ice towers, which are dozens of meters high, seem to be carved out of white marble. They stand on the glacier, facing the sky. Some look like the spires of the Great Wild Goose Pagoda and Little Goose Pagoda in Xi'an, some like the pyramids on the Nile River in Egypt, some like a doggy camel, and some like sharp swords reaching out to the sky.

Ice Mushroom: The horny peaks around the glacier, often constantly falling down debris fragments. If the rock mass that collapses is small, it will be melted when heated and warmed in the sun. As a result, the rock mass will sink into the ice, form a cylindrical ice cup, and then form an ice lake. If a larger volume of rock covers the glacier, it causes differential melting. When the surrounding ice has completely melted, and the large rock blocks the solar radiation, the ice under it can grow into different sizes. Ice mushroom.

Glacier movement

Glacier Introduction

In the early nineteenth century, in the Alps, several climbers were unfortunately buried in glacial grain basins by avalanches. At that time, a glacier worker speculated that the bodies of these people would appear in front of the tongue in forty years. Sure enough, forty-three years later, the bodies of these unfortunate people appeared in front of the tongue, and the survivors of the climber companions quickly identified the bodies.

In 1827, a geologist built a stone hut on the Eagle Glacier in the Alps. Thirteen years later, it was found that the cottage moved 1428 meters downstream. The hut itself does not move. The reason for the hut movement is that the foundation of the hut moves down with the glacier and moves the hut with it.

Glacier movement is somewhat similar to water flow, with fast middle and slow sides. If you insert a row of flower rods across the glacier, it doesn't take long to find out that the flower rod in the middle runs far ahead, and the original straight flower rod connection becomes an arc protruding downstream. . Many marine glaciers have very strange arc-shaped arches, which are caused by the speed of the middle and sides of the glacier.

There are often many cracks on the surface of glaciers, some of which are tens of meters deep. The existence of cracks indicates that the glacier is brittle. However, after hundreds of years of investigation and observation, fissures on the glacier rarely exceed 60 meters deep. Most crevices close well below this depth. This shows that the lower part of the glacier is plastic, and it can adapt to various external forces "softly" without breaking. Therefore, the glaciers can be divided into two layers. The layer that easily breaks on the surface is called the brittle zone, and the lower "soft" layer is called the plastic zone. The existence of plastic bands is the root cause of glacial flow.

Glacier movement

In order to adapt or eliminate external forces, the object can undergo three types of deformation, namely elastic deformation, plastic deformation, and brittle deformation (or fracture). Generally, an object has these three deformation stages when it is stressed. For example, a spring is generally elastically deformed; when the force exceeds the elastic strength, it is plastically deformed, and the spring cannot return to its original position; when the force is too large to exceed the burst strength, the spring is broken and deformed brittlely. However, there are masters and slaves in these three stages, and the three stages are not equally divided. What kind of deformation mainly depends on the nature of the material itself.

As far as ice is concerned, it is easy to show plastic deformation because it easily realizes the internal sliding of crystals. However, when the external force suddenly increases, it is easy to exceed the breaking strength of ice and cause brittle deformation (fracture). Only under slow loading and long-term stress can ice fully exhibit the characteristics of plastic deformation. We know that when an object is subjected to a long-term force, even if the force is small, plastic deformation will occur. In the lower part of the glacier, due to the pressure of the upper ice layer and the thrust of the upstream ice layer, it is always in a stressed state, so that the plasticity of the lower ice layer is more adequate. At the same time, the melting point of the lower ice layer is slightly lower than the upper ice layer, which makes the lower ice layer closer to the melting point, so that plastic deformation is easier to achieve. In this way, it is not difficult to understand that plastic bands appear in the lower part of the glacier. The glacier surface lacks the important condition of long-term stress. When the external force suddenly increases, it often deforms elastically or brittlely and becomes a brittle zone.

In an unobstructed valley, the maximum velocity of glaciers appears on the surface of the glacier as it flows, and the velocity decreases as the valley bottom approaches. This type of movement is called gravity flow. If during the glacier movement, a block of protruding bedrock or slowing ice blocks is encountered in front of the glacier, there will be a pre-extrusion and post-compressive shear stress there. This flow method is called blocking gravity flow. Where blockage of gravity flow occurs, there are often many reverse faults in the ice, as well as complex folds.

Glacier speed

The speed of glacier movement is only a few centimeters per day, and the number is not more than a few meters, so that the naked eye cannot detect that the glacier is moving. Some glaciers in Greenland have the highest speed in the world, but they only move more than a thousand meters each year. Glaciers in other areas, like some of the more famous Alps, have an annual flow rate of only 80 to 150 meters. Most glaciers in China are continental glaciers, the accumulation of glaciers is not abundant, and the material circulation on glaciers is relatively slow, which results in relatively low glaciers.

The speed of glaciers varies seasonally, with fast summers and slow winters. The glaciers of Tianshan and Qilian Mountains generally move 50% faster in summer than in winter (both referring to the tongue). One of the reasons for this difference is the change in glacier temperature. When the glacier warms, the viscosity of ice decreases rapidly, increasing from -20 ° C to -l ° C, and the viscosity of ice decreases almost linearly with temperature. Decreasing viscosity increases plasticity, and therefore the speed of glacier movement. The appearance of melted ice inside and at the bottom of the glacier in summer is another reason for the rapid movement of the glacier.

Glacier movement is generally very slow. However, some glaciers have a weird temper, and after a long period of slow motion or retreat, they suddenly advance forward explosively.

Glacier moving fastest

The Columbia Glacier between Anchorage and Valdez, Alaska, USA is 54 kilometers long, 4.8 kilometers wide, and its highest point is 910 meters. In 1999, it moved at an average speed of 35 meters per day. It has doubled in the past 20 years.

Glacier

Explosive propulsion occurs periodically on such glaciers and is a special way of glacial movement. People call this phenomenon "glaciers" of glaciers, and glaciers with wave properties are called "moving glaciers".

Glacier "waves" often cause extreme floods. There is a glacier in the upper reaches of the Indus River, which periodically enters the main valley. When it intercepts the river, it forms a large lake. Later, the lake breaks down, and a large flood is formed, causing disaster. The catastrophic floods that occur periodically in the Yeerjing River in Xinjiang may also be related to the glacial lake collapse caused by "glacial fluctuations".

Glacial action

Glacier erosion

Glaciers have a strong erosive force, most of which are mechanical erosive effects, and their erosion methods can be divided into several types:

Glacier scene (1) Erosion: When the bedrock at the bottom of the ice sheet or the back of the ice bucket is repeatedly frozen and thawed along the joint, if these loose rocks and the glacier are frozen together, the rock block will be pulled up when the glacier moves Take away, this is called eroding. After the erosion, the slope curve of the glacier river valley is rugged, forming a trapezoidal slope profile curve.

(2) Abrasive effect: When the glaciers move, the rock fragments frozen on the bottom of the glacier or ice layer, due to the pressure of the glacier above, grind and etch the bottom of the glacier, which is called abrasion. Abrasion can form a polished surface with abrasions on the bedrock, and the abrasions or grooves are a good evidence of glacial action, and its direction can be used to indicate the direction of glaciers.

(3) Ice wedge action: After repeated freezing and thawing, the ice-thaw water contained in the rock fractures will shrink and increase in volume, causing the rock layer to break up, become fragments, or fall from the slopes on both sides into the glacier. mobile.

(4) Others: When the ice-melting water enters the river, it often contains a large volume of ice cubes, which will generate a strong impact to damage the rocks on both sides of the downstream.

Glacier erosion is affected by the following factors:

(1) The thickness and weight of the ice layer. The heavy ones are erosive.

(2) The speed of ice movement. The faster ones are more erosive.

(3) The number of stones carried. The more people carry the heavier, the stronger the erosion.

(4) The ground is rough or smooth. Rough ground is more vulnerable to erosion by glaciers.

(5) The nature of the bedrock. Those with soft bedrock are more susceptible to erosion.

(6) If the slope direction of the rock formation is consistent with the glacier movement direction, it will be easily eroded.

The eroded landforms caused by erosion are:

(1) Ice bucket: It is one of the important ice-covered landforms in the valley and glaciers. It is formed near the snow line and has the most snow accumulation in gentle mountains or low-lying places. Due to the repeated freezing and thawing of snow, the rock disintegrates. Under the action of water, the rocks are eroded into half-bowl or horseshoe-shaped depressions, and typical ice buckets are formed. The three sides of the ice bucket are steep rock walls, and there is a mouth on the downhill. If the glacier subsides, the depression will become a lake, that is, the ice bucket lake.

(2) Blade ridges, angle peaks, and ice: If the ice bucket continues to expand due to erosion and frost erosion, the wall of the ice bucket recedes, and the ridge between adjacent ice buckets is gradually thinned to form a blade shape. Called the blade ridge. The peaks where several ice buckets meet are sharp and are called corner peaks. It is frosty at the lower saddle between the ridges.

(3) Cut off the mountain mouth, U-shaped valley, and rock depressions: When the valley glaciers move from high to low, the mountain mouth is flattened into a triangle, which is called cut off the mountain mouth. Because the cross-sectional shape of the glacier valley is U-shaped, it is called a U-shaped valley. There are obvious valley shoulders on both sides of the U-shaped valley. The valley walls below the valley shoulders are relatively straight, and the bottom is wide and flat. Ground.

(4) Fjord: In high latitudes, glaciers can often reach the ocean and erode into some deep U-shaped valleys on the shore. When the ice recedes, the seawater can go far along the valley, and the original ice valley becomes Fjord.

(5) Hanging valleys: The formation of hanging valleys is due to the difference in erosivity of the glaciers. The main glaciers are deeper in U-shaped valleys due to the thick ice layer and strong erosive force; while the supporting glaciers are thinner and have lower eroding force Therefore, the U-shaped valley is shallow. Because at the intersection of the branch glacier and the main glacier, there are often disparities in the height of the glacier. When the ice of the branch glacier enters the main glacier, it must fall into a waterfall shape, which is called hanging valley.

(6) Sheepback: It is an eroded terrain on the glacier base. It is a hillock composed of bedrock. It is often distributed in groups. Its plane is ellipsoidal, the long axis direction is consistent with the direction of ice flow, and the slope towards the upstream of the glacier is flat due to the abrasion of the glacier. The slope is slower and there are many scratches. On the other side, Due to the eroding effect of the glacier, the slope is rough and the slope is relatively steep. Sheepback is formed because the rock formations are arranged in a soft and hard phase. When the action of erosion and weathering is checked, the soft rock formations will be eroded more and deeper; and the hard rocks are more resistant to erosion and weathering. Therefore, after erosion and weathering, the hard rock formation will be higher than the soft rock formation, and the ellipsoidal terrain of the bulging shape will be abraded on one side and eroded on the other.

(7) Glazed surface and glacial scratches: On sheep's back or U-shaped valley walls and on large boulder, polished surfaces are often formed due to the effect of glaciers. When glaciers carry sand and silt On denser rocks, the polished surface is more developed; if the glacier is gravel, the valley wall is etched into stripes or grooves, which is called a glacial scratch. The end of the scratch is thick, and the other is One end is thin and the thick end points upstream.

Glacier transport

Due to the invasion of the glaciers, a large amount of loose debris and debris that fell from the hillside will enter the glacial system and move along with the glacier. These carried debris are called morains, depending on their differences in the glacier. Location can be divided into different types of handling:

(1) Table surface: Mortars exposed on the surface of a glacier.

(2) Inner ridges: Moraine objects trapped in glaciers

(3) Bottom ridge: a moraine piled on the bottom of a glacier valley.

(4) Side ridges: Moraine deposits on both sides of the glacier.

(5) Zhongli: After two glaciers merge, their adjacent side ridges merge into one, which is located in the middle of the glacier after the meeting.

(6) Final ridge (tail owl): The moraine that surrounds the end of the glacier as it progresses along the glacier is called the terminal ridge.

(7) Retreat: As the glacier retreats, a short stop will occur locally, and each stay will cause a retreat.

(8) Drifting stones: The function of glaciers can not only move the moraine to a long distance, but also move huge rocks to high sections. These huge rocks are called drifting stones. Its lithology is completely different from the bedrock near the site. Glaciers have strong carrying capacity, but relatively, they have poor panning capabilities.

Glacial deposition

The gravel carried by glaciers is often thrown along the way, so after the glaciers melt, the materials carried in different forms accumulate to form corresponding morains. The so-called moraine refers to the non-layered ice deposits directly caused by glaciers. Ice deposits refer to substances deposited directly by glaciers, or deposits due to the action of ice water, and substances deposited in rivers, lakes, and seas due to the action of glaciers. Ice deposits can be divided into two types: non-layered ice deposits and layered ice deposits:

(1) Non-layered ice deposits: This type of ice deposits are caused by the gravel left when the glacier recedes. The deposits left on the ground due to melting ice vary in size. The stones are less angular, The surface is polished or scratched, and there is no layering after accumulation. This kind of messy and unlayered ice deposits are often called boulder soil and the moraine terrain formed by morains includes:

Moraine hills (basement hills): After the glacier melts, the inner surface of the original surface is all sinking to the bottom of the glacier valley. Together with the bottom of the glacier, it is called the basement. These morains are affected by the topography of the glacier valley and accumulate. The sloping hills are called Moraine Hills. The moraine hills on the mainland's glacial regions are larger, while the moraine hills formed by valley glaciers are much smaller.

Side dyke: The side dyke and surface dyke are piled together at the glacier retreat. They are located on both sides of the glacier valley. They form an embankment to the upper reaches of the glacier and reach the vicinity of the snow line. The downstream can often be connected to the terminal dyke. .

The terminal embankment: The terminal embankment reflects the temporary pause stage when the glacier recedes. If the recharge and melting of the glacier is in a balanced state, the end of the glacier can stay at a certain position. Matter, which will accumulate in the shape of an arc at the end of the glacier, is called the terminal embankment. Continental glacier's terminal gully has a small height, up to several hundred kilometers in length, and has a small curvature. On the other hand, valley glacier's final gully can reach hundreds of meters in height, with a small length and large curvature.

Guqiu: Guqiu is a kind of hills composed of ice deposits. It is approximately elliptical. Its long axis is consistent with the direction of the water flow. The ice-facing surface is a steep slope. The ice-bearing surface is a gentle slope. Its longitudinal section is asymmetrical. Convex. It is generally believed that the gullocks are formed due to the weakening of the carrying capacity of the glacier. It is mainly distributed within a few kilometers to several tens of kilometers within the glaciers of the mainland. It often appears in groups, causing Guqiu fields; the number of Guqiu in valley glaciers is relatively small.

(2) Layered ice deposits: This is the result of the co-deposition of glaciers and melting ice water. The materials carried by the glaciers are washed and washed by the melted ice water, and will be stacked into layers according to the size of the particles. Ice water deposits, and various landforms composed of ice water deposits at the edge of the glacier are called ice water deposit landforms. There are the following types:

Ice water deposits, ice water fans, and outburst plains: A large amount of grit carried by ice-melt water at the end of a glacier accumulates in the valley or plain in front of the glacier to form ice water deposits; if it is at the end of a continental glacier, this type of The sediments can stretch for several kilometers, and they are piled into a fan-shaped land on the periphery of the terminal bank. They are called ice-water fans. Several ice-water fans are connected to form a vast ice-water alluvial plain, also known as the Waichong plain. On these terrains, the sediments show a gentle slope tendency downstream, and the granularity also decreases downstream.

Ice water lake and seasonal mud: Ice water lake is formed by ice-melt water, because when the glacier recedes, the ice deposits in front will block the glacier's path, and it can often accumulate water into a lake. The ice-water lake has obvious seasonal changes. In summer, there is more ice-melt water, and a large amount of material enters the lake. Some coarse particles are quickly deposited, and fine particles are suspended in the water, and the color is lighter. Reduced, some long-term suspended fine-grained clay began to settle, and the color was darker. In this way, two layers of thick and thin layers are easily identified in the lake, which are called monsoon mud.

Boulder port: The boulder port is composed of layered and sorted fine silt and has round or irregular hills. There is usually a layer of moraine in the upper part of the boulder port. The boulder port is caused by the sediments in the small lakes or rivers or stagnation of glacial glaciers on the ice. The difference is that the shape of the ice port is very irregular and layered. There are boulders on continental glaciers and valley glaciers.

Glacier Terrace: On both sides of the glacier, because the rock walls and side ridges absorb more heat, and the ice surface on both sides of the glacier is lower than in the middle, the ice melt water is collected here to form the ice-side river, and Bring icy water substances. After the ice water disappears, these materials will accumulate on both sides of the glacier valley, forming a boulder port terrace, which only develops in valley glaciers.

Pot cave (ice cave): There is usually a circular depression on the ice level, called a pot cave. Its formation is that when the glacier is depleted, some residual ice is isolated and buried in the ice water sediment. When the ice melts, it causes collapse and causes pot holes.

Snake-shaped mounds: Snake-shaped mounds are a long, narrow and tortuous terrain with a serpentine bay curve. The two walls are steep and the tops of the mounds are narrow. The direction of their extension is generally consistent with the direction of glaciers. The main causes of the serpentine mound are:

1. When the glacier melts, the ice melt water infiltrates the glacier along the glacial cracks, flows at the bottom of the glacier, and forms an under-ice tunnel. After the ice has completely melted, the gravel in the tunnel is deposited to form a serpentine mound.

2. In summer, ice melt water increases, and ice deposits form ice water deltas at the end of the glacier. When the next summer, the glacier recedes again to form an ice water delta, and so on and on, each ice water delta is connected. Beaded serpentine mounds have formed.

Glacier receding

Glacier Introduction

Due to the gradual warming of the global climate, the area and volume of glaciers around the world have decreased significantly, and some have even disappeared. This phenomenon is particularly pronounced at low and mid latitudes. ^[3]

Glacier status

Since 1980, the average thickness of the world's glaciers has decreased by about 11.5 meters, which is mainly attributed to climate warming caused by human abuse of fuels such as coal and oil.

The United Nations Environment Programme issued a statement saying that the world's glaciers have melted at the fastest rate in history, with European glaciers suffering the most, the main reason for this result is global warming. Researchers point out that because glaciers are one of the important freshwater resources, the rapid melting of glaciers will bring freshwater crisis to some regions, and even breed water conflicts in areas with scarce water resources.

The United Nations Environment Programme said in a statement that glaciers are melting faster from the Andes to the Arctic.

Data show that in 2006, the average thickness of the world's glaciers decreased by 1.5 meters, compared with 0.5 meters in 2005. The United Nations Environment Programme says this is the fastest time for glaciers to melt since monitoring by researchers.

The staff of the World Glacier Monitoring Center said that compared to other regions, glaciers in the European mountain areas suffered the most damage, including the Alps, Pyrenees and Nordic mountains. Africa's Mount Kenya glaciers lost 92%, while Spain had 27 glaciers in 1980, reducing the number to 13. The European Alps have lost half of their glaciers in the past century. Since the beginning of summer in 2003, heat waves that have swept across Europe have brought local temperatures close to or exceeding historical records. In Switzerland, the temperature of the 3,900-meter-high Fairpex Snow Mountain peak reached 5 ° C, where the thickness of the glacier fell to its lowest point in nearly 150 years.

In Tianshan, about 22% of the glacier volume has been lost over the past four decades. Tianshan is China's largest glacier area, with a total of more than 6,890 glaciers and a total area of about 9,500 square kilometers. The glaciers in northern and southern Xinjiang have been shrinking, with glaciers retreating to varying degrees. The Urumqi River originates from the Tiangel Peak No. 1 Glacier in the Tianshan Mountains. The annual runoff of the river is 235 million cubic meters. It is the main source of water in Urumqi. 140 meters. At the end of the 20th century, the glaciers of the Qilian Mountains shrank, and the melting water was reduced by about 1 billion cubic meters compared with the 1970s. The snow line in some areas of the glacier is rising at an average annual rate of 2 to 6.5 meters, and the snow line in some areas has risen at an average annual rate of 12.5 to 22.5 meters.

In the Himalayas, one of the largest glaciers has been shortened by more than 300 meters since 1935. At the end of the 20th century, the melting of the East Rongbu Glacier and the Middle Rongbu Glacier in the Everest region intensified, causing the glaciers to shrink significantly. By the 1980s, due to the opening of the Everest region, the number of people who climbed, explored, and traveled in the area increased rapidly. The local people had built the yak passage to an altitude of 6,500 meters. A study by the International Snow and Ice Council shows that glaciers in the Himalayas are accelerating, as evidenced by the rapid rise in water levels in nearly 50 glacial lakes in the Himalayas. Scientists predict that the Himalayas will shrink by a fifth over the next 35 years.

Scientists in the United States and Canada have announced that the 3,000-year-old Arctic ice shelf "Boss" Hunt has disappeared near the northern coast of Ellesmere Island, Nunavu, Canada. Through radar surveys, they learned that in 2000, a small crack appeared in Ward Hunt, which was 388.5 square kilometers in size. In 2002, the crack expanded to 77 meters, and some new cracks appeared next to it. A piece of 6 square kilometers The ice floes had separated, floating near Ward Hunt, and predicted that Ward Hunt would eventually split into two. The Greenland ice sheet in the Arctic has been thinning at a rate of 1 meter per year since 1993 at the southern and eastern edges.

The Antarctic ice sheet, which accounts for 91% of the world's ice reserves, has lost 1/7 of the total ice body area since 1998. At the end of last year, the American Geographical Society reported that the three largest glaciers in Antarctica had thinned and lost 45 meters in thickness over a decade.

The speed at which glaciers are shrinking is indeed quite amazing. In the Lima region of Peru, glaciers were melting at a rate of 30 meters per year from the end of the 20th century, but before 1990, the melting rate was only 3 meters per year.20501/4210050%

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The main peak of the Yulong Snow Mountain in Yunnan, with a steep elevation of 5596 meters, is the southernmost distribution area of modern glaciers in China. There are 19 glaciers on both sides of the ridge, with a total area of 11.61 square kilometers and an average area of 0.61 square kilometers. Baishuihe Glacier No. 1 is one of the largest glaciers in Yulong Snow Mountain, with a length of 2.7 kilometers and an area of 1.52 square kilometers.

Glacier types and scale

Valley Glacier with the Largest Area, Longest Length, and Largest Ice Reserve: Yinsugeti Glacier

Glaciers in China are divided into glaciers, ice bucket glaciers, valley glaciers, flat-top glaciers, ice caps and ice fields according to their shape and scale. The valley glacier is a sign of the maturity of the mountain glaciers. It is large in scale, up to several kilometers to several tens of kilometers in thickness, and can reach several hundred meters in thickness. It has two distinct parts: grain snow basin and ice tongue. The Yinsugeti Glacier is located on the northern slope of Qiaogori Peak in the Karakoram Mountains, Xinjiang. The total length of the glacier is about 42 kilometers, the ice tongue length is about 4,200 meters, the glacier covers an area of 380 square kilometers, and the ice reserve is 116 cubic kilometers. First place.

China's largest ice sheet

The millions and tens of millions of square kilometers of glaciers covering the north and south poles are generally called ice caps, and the glaciers with a size of hundreds or thousands of square kilometers after the ice caps can be called ice sheets. In 1999, Chinese and American scientists discovered the Pratunga Ice Field in the Nagqu region of central Tibet. It is located at 89 ° 59 to 89 ° 20 east longitude, 33 ° 44 to 33 ° 04 north latitude, and covers an area of 422.85 square kilometers. It has been confirmed to be the largest glacier in the world except for the polar regions, and it is also the largest glacier in the middle and low latitudes.

The largest ice cap: Chong test ice cap

An ice cap is a covered glacier that is smaller in size than an ice field, similar in shape, and more dome-shaped. The Chongce Ice Cap is located in the Kunlun Mountains in the northwestern Tibetan Plateau, 35 ° 14 north latitude, 81 ° 07 east longitude, and the top elevation is 6,580 meters. With an area of 163.06 square kilometers and an ice reserve of 38.16 cubic kilometers, it is China's largest ice cap.

China has measured the largest ice thickness of the valley glaciers: Dagongba Glacier in Gongga Mountain

At present, the largest ice thickness measured in China's valley glaciers is the Dagongba Glacier in Gongga Mountain, Sichuan, with an elevation of 4380 meters and a thickness of 263 meters. It is 4.47 kilometers from the end of the ice tongue.

The largest ice waterfall: Hailuogou Glacier Ice Waterfall

Glaciers flow on steep slopes, and the ice body is in a falling or sliding state. It is shaped like a waterfall and is called an ice waterfall. The Hailuogou Glacier Ice Waterfall in Gongga Mountain, Sichuan is the largest ice waterfall known in China, with a height of 1080 meters and a width of 500-1100 meters.

Hailuogou Glacier, Gongga Mountain, Sichuan, 2007

The lowest glacier at the end of China: Kanas Glacier

The Kanas Glacier is located at the Friendship Peak of the Altai Mountains in Xinjiang. It is a double valley glacier composed of two ice streams. It is 10.8 kilometers long, covers an area of 30.13 square kilometers, has an ice reserve of 3.93 cubic kilometers, and the end of the glacier is 2,416 meters above sea level. The lowest glacier.

In recent years, many glaciers have been awarded the title of "lowest glaciers". Among them, the more famous glaciers have their end heights checked in the glacier catalog. The results are as follows: Aza Glacier, with an end elevation of 2,450 meters; Ka Qin Glacier, the end elevation is 2530 meters; Mingyong Glacier, the end elevation is 2700 meters; Hailuogou Glacier, the end elevation is 2980 meters. In this way, Kanas Glacier seems to be the well-deserved lowest glacier at the end. However, due to the impact of climate change, many glaciers have receded very seriously. The altitude of the end of the glaciers is not stable, and the ratio of the data recorded on the glacier catalog may also occur Therefore, in the strict sense, the lowest glacier at the end cannot be easily judged. ^[4]

According to Reuters, radar on NASA's Mars Reconnaissance Orbiter (MRO) has detected a huge ancient glacier beneath the Martian rock pile, which may be the remnant ice of a large ice sheet covering Mars in the previous ice age.

Planetary geologist John Holt says these glaciers are the largest glaciers we know outside Mars' North Pole. These glaciers will be used as drinking water and rocket fuel for future manned missions to Mars. "If we really go to Mars and build a human base on Mars, you have to stop by a large water source, because you can use water at any time."

Geologist James Hurd of Brown University in the United States said that the glacier may be 200 million years old and may contain genetic fragments of ancient Martian organisms. Air bubbles in glaciers can also reveal the composition of Mars' ancient atmosphere. Data collected by the radar on the Mars Reconnaissance Orbiter confirmed that the buried glaciers did exist, stretching tens of kilometers from the cliffs or foothills. These glaciers are like glaciers on Earth's Antarctica, all covered with rock piles.

^[5]