Do glaciers affect people?
Today, glaciers often are tourist attractions in mountainous areas. But glaciers are also a natural resource, and people all over the world are trying to harness the power of these frozen streams.
- Glaciers Provide Drinking Water
People living in the city of La Paz, Bolivia, rely on glacial melting from a nearby ice cap to provide water during the significant dry spells they experience.
Although parts of Japan receive tremendous amounts of snow, there are no glaciers. Because the Japanese must endure frequent droughts, scientists are examining ways to create artificial glaciers that could provide more water for people when the weather is dry.
Over a thousand years ago, farmers in Asia knew that dark colors absorb the solar energy. So, they spread dark-colored materials such as soil and ashes over snow to promoted melting, and this is how they watered their crops in the springtime. Chinese and Russian researchers have recently tried something similar by sprinkling coal dust onto glaciers, hoping that the melting will provide water to the drought-stricken countries of India, Afghanistan, and Pakistan. However, the experiment proved to be too costly, and they have abandoned the idea.
In Switzerland's Rhone Valley, farmers have irrigated their crops for hundreds of years, by channeling meltwater from glaciers to their fields.
- Glaciers Help Generate Hydroelectric Power
Scientists and engineers in Norway, Canada, New Zealand and the Alps have worked together to tap into glacial resources, using electricity that has been generated in part by damming glacial meltwater.
How do glaciers affect the land?
Glaciers not only transport material as they move, but they also sculpt and carve away the land beneath them. A glacier's weight, combined with its gradual movement, can drastically reshape the landscape. Over hundreds or even thousands of years, the ice totally changes the landscape. The ice erodes the land surface and carries the broken rocks and soil debris far from their original places, resulting in some interesting glacial landforms.
Common all over the world, glaciated valleys are probably the most readily visible glacial landform. Similar to fjords, they are trough-shaped, often with steep vertical cliffs where entire mountainsides were removed by glacial action. One of the most striking examples of glaciated valleys can be seen in Yosemite National Park, where glaciers literally sheared away mountainsides, creating deep valleys with vertical walls.
Fjords, such as those in Norway, are long, narrow coastal valleys that were originally carved out by glaciers. Steep sides and rounded bottoms give them a trough-like appearance. Because of glacial erosion on the below sea level land surface, when glaciers finally disappear, sea water covers the valley floor.
The famous Matterhorn in Switzerland displays three types of glacial erosion:
- Cirques are created when glaciers erode backwards, into the mountainside, creating rounded hollows shaped like a shallow bowls.
- Aretes are jagged, narrow ridges created where the back walls of two cirque glaciers meet, eroding the ridge on both sides.
- Horns, such as the famous Matterhorn in Switzerland, are created when several cirque glaciers erode a mountain until all that is left is a steep, pointed peak with sharp, ridge-like aretes leading up to the top.
Fjords, glaciated valleys, and horns are all erosional types of landforms, created when a glacier cuts away at the landscape. Another type of glacial landform is created by deposition, or what a glacier leaves as it retreats or melts away.
Till is material that is deposited as glaciers retreat, leaving behind mounds of gravel, small rocks, sand and mud. It is made from the rock and soil ground up beneath the glacier as it moves. Glacial till can form excellent soil for farmland.
Material a glacier picks up or pushes as it moves forms moraines along the surface and sides of the glacier. As a glacier retreats, the ice literally melts away from underneath the moraines, so they leave long, narrow ridges that show where the glacier used to be. Glaciers don't always leave moraines behind, because sometimes the glacier's own meltwater carries the material away.
Streams flowing from glaciers often carry some of the rock and soil debris out with them. These streams deposit the debris as they flow. Consequently, after many years, small steep-sided mounds of soil and gravel begin to form adjacent to the glacier, called kames.
Kettle lakes form when a piece of glacier ice breaks off and becomes buried by glacial till or moraine deposits. Over time the ice melts, leaving a small depression in the land, filled with water. Kettle lakes are usually very small, and are more like ponds than lakes.
Glaciers leave behind anything they pick up along the way, and sometimes this includes huge rocks. Called erratic boulders, these rocks might seem a little out of place, which is true, because glaciers have literally moved them far away from their source before melting away.
Drumlins are long, tear-drop-shaped sedimentary formations. What caused drumlins to form is poorly understood, but scientists believe that they were created subglacially as the ice sheets moved across the landscape during the various ice ages. Theories suggest that drumlins might have been formed as glaciers scraped up sediment from the underlying ground surface, or from erosion or deposition of sediment by glacial meltwater, or some combination of these processes. Because the till, sand and gravel that form drumlins, are deposited and shaped by glacier movement, all drumlins created by a particular glacier face the same direction, running parallel to the glacier's flow. Often, hundreds to thousand of drumlins are found in one place, looking very much like whalebacks when seen from above.
How do glaciers reflect climate change?
Glacial ice can range in age from several hundred to several hundreds of thousands years, making it valuable for climate research. To see a long-term climate record, an ice core is drilled and extracted from the glacier. Ice cores have been taken from around the world, including Peru, Canada, Greenland, Antarctica, Europe, and Asia. These cores are continuous records providing scientists with information regarding past climate. Scientists analyze various components of cores, particularly trapped air bubbles, which reveal past atmospheric composition, temperature variations, and types of vegetation. Glaciers literally preserve bits of atmosphere from thousands of years ago in these tiny air bubbles. This is how scientists know that there have been several Ice Ages. Past eras can be reconstructed, showing how and why climate changed, and how it might change in the future.
Scientists are also finding that glaciers reveal clues about global warming. How much does our atmosphere naturally warm up between Ice Ages? How does human activity affect climate? Because glaciers are so sensitive to temperature fluctuations accompanying climate change, direct glacier observation may help answer these questions. Since the early twentieth century, with few exceptions, glaciers around the world have been retreating at unprecedented rates. Some scientists attribute this massive glacial retreat to the Industrial Revolution, which began around 1760. In fact, some ice caps, glaciers and even an ice shelf have disappeared altogether in this century. Many more are retreating so rapidly that they may vanish within a matter of decades. Scientists are discovering that production of electricity, along with coal and petroleum use in industry, affects our environment in ways we did not understand before. Within the past 200 years or so, human activity has increased the amount of carbon dioxide and other greenhouse gases released into the atmosphere.
The 1991 discovery of the 5,000 year-old "ice man," preserved in a glacier in the European Alps, fascinated the world (see National Geographic, June 1 1993, volume 183, number 6, for an article titled "Ice Man" by David Roberts). Tragically, this also means that this glacier is retreating farther now than it has in 5,000 years, and no doubt other glaciers are as well. Scientists, still trying to piece together all of the data they are collecting, want to find out whether human-induced global warming is tipping the delicate balance of the world's glaciers.
Original Source: National Snow and Ice Data Center
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