GLACIERS IN TIBET
The Qinghai-Tibetan plateau has the third largest number of glaciers after Antarctica and the Arctic. Glaciers in the Himalayan region make up the greatest concentration of ice outside the polar regions. Mountain glaciers are vital for providing a steady stream of water that feeds streams, rivers, lakes, agriculture and provides water for fish.
According to the World Wildlife Fun (WWF), China has 36,793 glaciers that cover 49,973 square kilometers and have an ice volume of 4,561 square kilometers. Glaciers feed several of the world’s great rivers. The Ganges, Indus, Brahmaputra, Mekong, Yangtze and Yellow rivers---are fed by glaciers in the Himalayas and Tibet.
A glacier is a great river of ice that forms in places where snowfall exceeds melting. There are two kinds of glaciers: 1) mountain glaciers , which flow down hill in between mountains; and 2) continental glaciers, country-size glaciers that cover large masses of land. These days the continental glaciers are found exclusively on Greenland and Antarctica. During the Ice Ages, they covered much of northern Europe and North America.
Large glaciers take thousands of years to become established. They begin as snowfields, large deposits of snow that exist throughout the year but are distinguished from glaciers by the fact they don't move downhill.
In direct sunlight or warm weather the snow on the surface of a glacier melts. The dripping water and pressurized snow becomes ice as layers of snow are piled on top of them. When the ice and snow of snowfield become significantly high, usually at a depth of around 60 feet, the entire mass begins moving downhill and becomes a glacier. Like rivers they flow down through places that offer the least resistance, usually downward-slopping valleys.
In places with dry lowlands and a dry season, glaciers and snow pack from the mountains are a vital sources of water after spring melt. All winter the mountains collect water like as if they were reservoirs and release it during the spring thaw and deliver it when lowlands need it the most.
Good Websites and Sources on Tibetan Environmental Issues: Tibet Environmental Watch tew.org ; tibet.org ; CNN report on China Exploiting Tibetan Resources money.cnn.com ; China Daily report on Huge Mineral Resources in Tibet chinadaily.com ; Free Tibet on Mineral Extraction freetibet.org ; Global Warming and Tibetan Glaciers The Independent ; China Daily on Global Warming in Tibet chinadaily.com
Mountains: China Trekking China Trekking ; Summit Climb Summit Climb ; Trekking Tibet Trekking Tibet ; Samrat Nepal Samrat Nepal ; Himalayas Wikipedia article on the Himalayas Wikipedia ; Making of Himalayas geol.unibas ; Himalayas site himalayas.dk ; Mt. Everest : Wikipedia Wikipedia National Geographic National Geographic Mount Everest.net Mont Everest.net Summit Post Summit Post ; Glaciers: All About Glaciers nsidc.org ; Wikipedia article on Glaciers Wikipedia ; Wikipedia article on Avalanches Wikipedia
Links in this Website: TIBETAN NATURE Factsanddetails.com/China ; Factsanddetails.com/China ; MOUNTAINS IN TIBET Factsanddetails.com/China ; GLACIERS AND AVALANCHES IN TIBET Factsanddetails.com/China ; TIBETAN ANIMALS AND PLANTS Factsanddetails.com/China ; SNOW LEOPARDS Factsanddetails.com/China ; SHAHTOOSH AND CHIRUS Factsanddetails.com/China ; YAKS Factsanddetails.com/China
Advance and Retreating Glaciers
Glaciers flow like rivers but at a much slower rate. Slow-moving ones move at a rate of a few inches a day while fast-moving ones move several feet a day. Some glaciers don’t move. They are referred to a “cold glaciers “ because they are frozen to the bed.
An advancing glacier is one that it is getting longer because the amount of snow that falls on the glacier exceeds the amount of snow melting from it. A receding, or retreating, glacier is one that it is getting shorter because the amount of snow that falls on it is less than the amount of melting.
Most mountain glaciers have an upper zone, where the accumulation of snow outpaces melting, and a lower zone where the opposite is true. How far down the mountain a glacier extends depends on the equilibrium snowline---the boundary between the upper zone and the lower zone, which roughly corresponds the place where the temperature reaches the freezing point.. Sometimes tongues of the glacier extends below the equilibrium snowline. The size of a glacier is defined by the balance between the melting and downward push of the glacier.
A typical Alpine glacier resembles a hand. The palm is the main part of the glacier and where snow is accumulating and turning into ice. The fingers, sometimes called tongues or snouts, are rivers of ice that flow down various valleys and out of the mountains.
Tributary glaciers are similar to the streams that feed a river. They are created in upper reaches of the mountains, where they scrape off rock and pick up gravel and carry them with into the main glacier, resulting in the twisting, parallel black lines that you often see in large glaciers.
"Crevasses" are large cracks that occur in glaciers. "Icefalls" are areas where the glacier is moving relatively quickly and breaking apart, producing large areas of crevasses and jagged ice. "Calving" refers to large pieces of ice falling off the end of glaciers. This is usually associated with glaciers that terminate in bodies of water, which causes the ice to melt and fracture more quickly. After a calved piece of ice falls into the water it becomes an iceberg.
"Moraines" are the walls of debris that mark the edge of major Alpine glacier tongues. When the ice melts at the bottom of a glaciers, rock and soil are deposited. Over time large amounts of this debris accumulate into moraines.
Alpine Glacier Geological Features
Glacier pick up and carry massive amounts of rock and soils. These and the ice itself can wear away the hardest rocks and scour the landscape under and beside a glacier, creating a geological features associated with glaciers.
Alpine glacier features include: 1) "U-shaped valleys," mountain valleys that have been carved out by glaciers; 2) "hanging valleys," U-shaped valleys that are chopped off by a glacier going another direction, leaving a valley with a big cliff at its widest and lowest point (spectacular waterfalls often form here); 3) "cirques," bowl-like basins; 4) cols, sharp peaks created by glaciers wearing away rock from different sides of the peak.
Glaciers as we said before act like dams that store water in the winter and release it the summer when farmers most need it. But if too much water is released, such as during a spring heavy rain, when spring melting is at peak, flood can occur. Sometimes lakes created within glaciers burst their dams and cause catastrophic flooding.
When a glacier retreats, the land is occupied by a succession of plants, beginning with lichens, grasses and flowering plants. As they produce detritus that fertilizes the soil, mat-forming trees such as willows appear. Within about 50 years, thickets of alder trees have established themselves. A mature forest generally takes about 200 to 250 years to establish itself after a glacier is gone.
Friction between the glacier, its sediments and the rock beneath the glacier act as a brake and keep the glacier from flowing faster than it otherwise might. Scientists have long wondered why glaciers don’t slide at much faster rate. Some had speculated that bumps in the bedrock help to hold them up but recent data suggests that friction does most of the work. Water has a lubricating effect. Glaciers experiencing a lot of melting often move very fast.
As the snow descends into a glacier and more snow piles on top of it, applying pressure, its crystal structure breaks down and it changes to ice. When the ice reaches depths of over 2,000 feet it becomes so compacted that if it is brought to the surface and mishandled it will explode. Sometimes ice turns brilliant blue color. Green icebergs have been spotted.
Glacier ice much is more plastic than the ice in freezers. It is in constant motion, compressed by ice above and pushed downhill by its own weight. Glaciers groan, creak and crash as chunks of ice within the glacier bulge, press and rub against one another. On sunny or warm days, millions of gallon of snowbell filter down through a glacier, raising the water pressure where it meets the rock.
By some estimates in the past 50 years 82 percent of the Tibetan plateau’s glacier ice has melted. The plateau has lost 10 percent if its permafrost layer in the past decade.
Himalayan glaciers are melting at an alarming rate. More than 15,000 glaciers in the Himalayas show evidence of shrinkage, some of it quite dramatic. Many are shrinking at a rates of 70 meters to a 100 meters a year. Some 2,000 Himalayan glaciers have disappeared since 1900. Fifteen-mile-long glaciers have lost a third of their length in the last 50 years. Many scientists think the retreat is linked to global warming.
The shrinkage of Himalayan glaciers could result in water shortages that could affect more than 1 billion people, mainly people that rely on the Indus, Ganges, Brahmaputra, Mekong, Yellow, Yangtze and Salween rivers and their tributaries, which are fed by melt waters from Himalayan and Tibetan glaciers and snow.
According to a report by the WWF glacial melting is expected to increase even more. Initially the result will be flooding but this will be followed by a long steady decline of river flow that could have severe consequences on agriculture and fisheries.
One hydrologist told the Independent, "Glaciers tend to melt out in the summer and that is the time when a great deal of water is needed for agriculture. So it's precisely the time when water is most needed those glaciers give their water. And the threat is that in the future there won't be that water to use."
The melting glaciers have caused the levels of lakes to rise. The levels of 117 lakes in Nagqu prefecture have risen, The water level of Tibet’s second largest lake, Sering Ko, has rise 20 centimeters and grown to a size of 1,620 square kilometers. Since 1997, it has extended five kilometers to the west, 23 kilometers to the southwest, 3 kilometers to the south and 18 kilometers to the north. Rising water levels has submerged 106,667 hectares of pastureland and forced 1,400 household to build new homes.
Scientist are study the phenomena with satellites and trying to restore degraded grasslands.
Dangerous Glacier Lakes
Already increases in melting have caused some lakes in Nepal to overflow their banks and damage villages and hydroelectric facilities. Some farmers have prospered with a windfall of water that has flowed their way from melting glaciers.
Some Himalayan lakes are growing at a rapid pace as glaciers melt. The Tsh Rolpa lake in the Dolaka district in Nepal has grown from about a quarter of a square kilometer in the 1950s to 1½ square kilometers today. The Raphstreng Tsho glacial lake in Bhutan was 1.6 kilometers long and 80 meters deep in 1986 and today in two kilometers long and 127 meters deep.
Melting glaciers are producing huge glacier-fed lakes in valleys held back by weak natural earthen dams that are in danger of bursting and releasing torrents of water downstreamand threatening people who live in the river valleys downstream from the lake. Some call the danger “tsunamis from the sky.” Floods from such lake have killed in the past. One in 1994 killed 24 people in the river valley town of Punakha in Bhutan
Glaciers and Global Warming
Worldwide glaciers are shrinking. Many blame global warming, which seems to be causing more snowfall in the winter but also more melting in the summer.
The number of glaciers in Glacier National Park in the United States has dropped from 150 in 1910 to 30 today and most of the remaining ones have shrunk by two thirds. Glaciers in the park are disappearing so quickly they could be gone by 2030.
In the Caucasus half of all glaciers have disappeared in the last 100 years. Mt. Kilimanjaro’s ice cap has shrunk by half in the last 40 years and by 80 percent in the last 100 years. By some estimates it could be ice free in as little as 15 years. Glaciers in the some parts of the Alps and the Andes are shrinking at an alarming rate and some worry they could disappear in the coming decade.
Shrinking glaciers are not the case everywhere. In the 1980s and 1990s glaciers in Scandinavia, Greenland, Iceland and New Zealand were growing. In Alaska some are shrinking but others are stable.
The melting of glaciers isn’t necessarily tied to global warming. Scientists say it can take decades for a glacier to respond to warming and that melting that is occurring today is still partly the result of warming after the Little Age from 1450 to 1890.
Global warming could reduce winter snows and cause earlier spring melts disrupting water management and releasing water before people in the lowlands are ready. While global warming can increase melting it can also increase evaporation and produce snow-generating clouds.
Scientists studying glaciers examine snowfall records and stream flow data; drag ground -penetrating radar over crevasses; analyze soil carbon; and check in animals that live around glaciers. Studying the size and movement of glaciers in the past is difficult because as glaciers move they act like giant erasers, obliterating almost all traces of what happened before. Sometimes the most accurate way to analyze the size of glaciers in the past is to observe old paintings and photographs.
In northern Norway, scientists build temporary caves into the middle of glaciers to study the internal mechanism of glaciers. The caves are dug with warm-water jets. They begin shrinking almost as soon as they are dug and usually collapse within a couple of days. Among the things that scientists have discovered is that bottom of glaciers are filled with water pockets; and friction between sediments in the glacier and rock face is 20 times great than mathematical models predicted.
Scientists in Greenland are drilling deep into continental glaciers there to study climate change, air pollution and other things. The cores reach air pockets and ice that has been trapped for more than 100,000 years. Among the things that scientists have found are ash from the Krakatau explosion, lead pollution from ancient Rome, dust blown from Mongolia and signs that global warming is linked to human intervention.
Scientists study glacier movement dating organic objects found in them such as pieces of wood and plants and analyzing rocks found in deep sediment cores. Scientists are gaining insights into a number of fields by collecting objects that have been revealed as glaciers melts. The Iceman found in 1991 Europe is the most spectacular example of this. Frozen mummies have been found in Peru. Animals of various kinds have been found in glaciers all over the world.
Studying glaciers is often labor-intensive and time consuming. Hundreds of bamboo stakes and poles---often seven meters long---are stuck into the glacier. After a year or so the stakes are checked. The stakes at higher elevations will have snow piled around them and scientists can estimate the amount of snowfall there. The stakes at lower elevations reveal snow melt evaporation. Veteran glaciologist Ian Allison told Reuters, ‘so you can measure how much height is lowered down below, how much it gained at the top, you’ll need to know the density of the snow and ice as well.” The most carefully studied glaciers are in the Alps.
The process is often hard work. Often the glaciers are hard to reach and the equipment has to be carried in on foot or the backs of horses, mule or yaks. On top of that, especially in the Himalayas, many glaciers are in politically sensitive areas near the borders of India, China, Pakistan or Central Asia . In these places satellite phones and GPS devices are often banned.
Scientists studying glaciers and global warming sometimes carry carbon sensors, sensitive GPS systems and state-of-art, solar-powered weather stations with them on the backs of their pack animals. The teams are not all that different than those used by pioneering mountain surveyors and the first mountaineers to scale the major Himalayan peaks.
The largest natural avalanches occur in the Himalayas but no one has accurately measured them. Avalanches are landslide of ice and snow. Compared to mythical German monsters that fly without wings, sees without eyes and strikes without hands, they can reach speeds of 200mph; attain a mass of more than a million tons and produce forces 48 times stronger than those needed to demolish a frame house. Severe avalanche can snap trees like toothpicks, dump snow in 30-foot-high heaps and leave behind acres of destroyed buildings. [Source: National Geographic, September 1982]
Avalanches “may flow like rivers of icy cement, entombing everything in their path. Or they may hurtle like rockets, throwing before them blast waves that can blow houses apart and toss trucks like toys."
Describing a severe avalanche, David Cupp wrote in National Geographic, "At the start, an avalanche slab breaks off and fractures. As it gains speed the descending mass breaks up into a river of flowing snow, generating a cloud of snow that may roil upwards hundreds of feet. Inside the avalanche the dense core picks up more snow as it advances, accelerating in growth and speed...As velocity increases, the onrushing mass may rise and become airborne, riding friction free atop a cushion of air.
"The avalanche thunders down the mountain. Shock waves hit first...starting with a low whistle and swelling instantly to a screaming crescendo... Massive steel beams flex, bending and twisting as if made of rubber. As snow-laden wind shrieked through, the structure exploded. A third force, rampaging snow, destroyed almost everything still standing."
Avalanches are not dangerous because they occur but because people and property get in their way. The high population density is one of the main causes of avalanche disasters. More and more buildings are being built in harms way, more and more trees are being cleared and more resorts are being built higher and higher up in the mountains, where there is no avalanche protection from trees and avalanches are more likely to be triggered by high winds.
Causes of Avalanches
Avalanches occur on slopes pitched at angles greater than 20 degrees, with some 90 percent occurring on slopes of 20 to 45 degrees. On steeper slopes snow doesn't accumulate. On more gentle slopes, the snow doesn't slide.
The greater the snowfall the more likely an avalanche is to occur. Avalanches usually occur when a layer of snow called "sugar snow" (snow that doesn't bond well with other snow) cannot support the weight of additional snow and collapses, causing the top layers of snow to slide. Sugar snow is produced when water vapor condenses, forming loosely bonded crystals, when the temperature difference with the snowpack exceed 10̊C per meter. Unlike sugar snow, settled snow is cohesive and fairly compacted. It occurs when the temperatures in the snowpack are relatively uniform.
The worst kind of avalanches, slab avalanches, occur when a thick top layer of snow slips of a bottom layer of sugar snow. The deeper the sugar snow or the thicker the top layer, the more severe the avalanche is.
Wet snow forms strong bonds and is less likely to be involved in an avalanche than dry powder, which doesn't bond so well. The snow closer to the ground is generally warmer than the snow near the surface. It tends to give off vapor that passes through the upper layers of snow and condenses on the snow crystals, causing them to become angular "faceted crystals", which don't bond so well and make sugar snow.
Other factors that cause avalanches include: 1) strong winds that produce cornices (overhangs of snow) that can break off; 2) surface snow that melts and freezes, providing a perfect surface for sliding snow;. 3) accumulations of new snow more than an inch an hour; 4) fluffy layers of light snow that create an unstable barrier for snow above it.
Weather and Avalanches
One weather pattern that produces severe avalanches starts with dry, powder snow early in the season, which bonds less well than wet snow and is more affected by temperature change and can more easily change into sugar snow. If a weak unstable layer is topped by heavy snowfall all that is needed to set off an avalanche is a trigger such as high wind, stress from the weight of the snow, or even a loud noise or the weight of a skier.
The worst avalanches occur after severe storms that dump two or three feet of snow for four or five days on top of already deep snow pack. Another dangerous combination that occurs in coastal areas is when a blizzards is followed by a warm spell and the thresholds between new layers are lubricated by meltwater.
Trees help avalanches back and slws them down. Pollution and the development of ski resorts have striped many mountains of the trees, making avalanches a real problem. The threat of avalanches may or may not be made worse by global warming.
Avalanche Avoidance and Survival
1) Stay out of areas that have just had heavy snows. 2) Avoid slopes with chutes loaded with windblown snow. 3) Stay on the windward side of mountains. 4) Avoid terrain where an avalanche could carry you over a cliff or bury you in a gully. 5) If the snow settles with a "woomph" below you you could be in trouble
Stay out of dangerous back country areas. The dangers of avalanches have become greater since more and more skiers, snowboarders and snowmobiler are going off-piste, heading into back country areas and tackling steeper slopes at higher elevations. The people most vulnerable to avalanches sometimes trigger them.
Avalanche victims usually die of suffocation. They have an 86 percent chance of survival if they are found within 15 minutes because they are often buried with a little air to breath. There is a 50 percent chance of survival if found within 30 minutes. Only five percent of avalanche victims are found alive. The trick is finding them quickly before they suffocate.
Dogs, shovels, probing poles, beacons, metal detectors and long metal probes are used to find avalanche victims. Lasers are not useful because laser beams penetrates only half a meter. Many skiers and hikers carry beepers that can send and receive homing signals so they can be located under an avalanche.
If one is caught in an avalanche one should sit quietly and save their energy for a rescue. The average victim is buried under only a meter of snow. Why can't people just claw their way out? One reason is that after an avalanche runs its course the snow coalesces into an ice-like consistency.
A woman who was rescued after five days in a collapsed building under an avalanche told National Geographic that after she woke up "it was black; I had no idea where I was or what had happened." She was pinned under wooden lockers and survived by eating snow and wearing clothes pulled out of lockers near where he was strapped.
On the fifth day she became dangerously dehydrated as her supply of snow was running out. "I was just grabbing snow and eating it as fast as I could...I also prayed a lot that day,” she said.
The woman was rescued with the help of 150 rescuers, who dug through 15 feet of snow and debris, and German shepherd rescue dogs. "All of a sudden,” she told National Geographic, "there was a small area where some light shone through, and I saw snow sifting in. I was thirsty, and snow meant water. I grabbed for it ." When the rescuers saw her hand, one shouted, "Anna is that you?"..."I'm Ok, I'm alive," she called back.
Describing the ordeal of another survivor, Cup wrote. "As the building exploded, Jeff grabbed a counter top...The sound changed pitch, to a roar louder than anything Jeff had ever heard. He dived behind the counter as the wall behind him disintegrated...then he floated across the room disappearing in the whiteness...Jeff was hurled 100 feet and except for one hand, buried." He was dug out by a friend, who was protected by 22-ton concrete ski-lift counterweight. and survived.
One avalanche expert who was buried by an avalanche told National Geographic, he had a radio that he could use to call for help but when he was buried it took him 45 minutes to get his hands on the radio
Avalanche Prevention and Prediction
Avalanche prevention measures include 1) banning buildings in avalanche chutes and other danger zones; 2) erecting large walls outside resort towns to protect them form avalanches; 3) covering roads with reinforced roofs. Some places have zoning laws that restrict construction in high risk areas. Residents are often reluctant to go along with such measures. Many of the buildings destroyed by avalanches are relatively new, which implies that new buildings were built in avalanche-prone areas avoided by builders of the older buildings.
Other efforts to combat avalanche damage include preventing deforestation, planting trees, and utilizing avalanche forecasting systems, victim detection equipment, and building materials with greater strength and flexibility.
Avalanche patterns are often well known. Avalanches tend to occur at the same places year after year, often open slopes, bowls or gullies above tree line. Scientists are better at predicting avalanches and getting word to authorities to have people moved out of vulnerable areas before a dangerous avalanche can strike.
Scientists attempt to predict avalanches by determining when the snowpack is danger of giving way. To do this scientist typically dig away around a column of snow to determine how deep the sugar snow is. They also check the stress that top layers can bear by dropping weights on the surface of the snow.
Seismic studies have indicated avalanche patterns.
Avalanche Barriers and Explosives
A variety of fences, nets and barriers have been built to prevent avalanches. Avalanche-halting barriers include 300-foot-long earthen walls, giant one-ton boulders, funnels made with 75-foot-high concrete walls, snow barriers constructed of tripod-like concrete wharf-making materials and acres of iron netting to keep rocks in place. These barriers are often built at the avalanche starting zones.
Among the most effective avalanche barriers are long parallel fences made wood or steel. They are designed to stop or reroute avalanches away from buildings and people. The problem with them is they don't always work and they are expensive (about $1 million to save an area of 10,000 square meters).
One of the primary methods of avalanche control used at ski resorts in the Rockies and elsewhere in North America is setting of explosives to trigger small, controlled avalanches to avoid snow build up that can cause dangerous avalanches that can kill a lot of people. In the Alps there are often so many people and buildings in harms way that even small avalanches can not be triggered without risks. Most the dynamiting is done on steep slopes above the timberline.
The small avalanches are created by lobbing explosive devises by hand or firing 75mm or 105mm recoilless rifles into the snowpack. Hand explosives are used for places that can be reached by ski patrols. Cannons are used for places that are hard to get at. To bring down a cornice on a ridge an overland ski patrols set off 60 two-pound charges
Image Sources: NASA, Purdue University
Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
© 2008 Jeffrey Hays
Last updated July 2011