A glacier is a mass of thick ice that stays frozen and can move slowly over land. During the Ice Age, which ended about 10,000 years ago, many parts of the world were covered with glaciers. Almost all of Canada and the northern parts of Europe, like Scandinavia and Siberia were covered with ice.
Today, the large ice masses of the Ice Age are gone but there are still glaciers all over the world. Most of them exist high up in mountain regions but even around the equator there are places where snow falls and never melts.
How Glaciers form
Glaciers can form in places where the snow that falls in winter months cannot completely melt away during the summer. The layers of snow get thicker and thicker. When it melts and freezes over and over again it turns into ice. This ice can become very heavy and starts to move down valleys.
The speed at which glaciers move depends on the climate. When it gets colder glaciers get bigger and move downwards. When it gets warmer over a longer period of time glaciers melt and retreat back to the tops of the mountains. In some cases glaciers can move up to 1 km or even more every year. When a glacier moves over land slowly it picks up rock and dirt and carries these materials along with it. When a glacier comes to a standstill it piles up this material to form moraines. The gigantic weight and power of glaciers can even reshape mountains. This happened to the Alps and other mountain ranges during the Ice Age.
The earth’s glaciers hold about 75 % of the world’s freshwater. Many people think that if temperatures around the world increase, more and more ice will melt. Sea levels will go up and flood many coastal areas.
Types of Glaciers
Valley glaciers grow high up in the mountains. They form in places where it stays cold the whole year and where snow falls even in the summertime. These glaciers flow down valleys and start to melt when it becomes too warm. Over the years rivers of ice have carved out many mountain valleys and given them the shape we see today.
Near the equator such glaciers can be very short, maybe only two or three kilometers, but in North America and Europe valley glaciers are much longer and larger. The Lambert Glacier in Antarctica is the longest in the world. It has a length of 700 km. The Aletsch Glacier in Switzerland is about 23 km long. Austria’s longest glacier is the Pasterze, which lies at the foot of the Großglockner and is about 8 km long.
The Aletsch Glacier in Switzerland -Didier Baertschiger
Ice caps and ice sheets
When a glacier lies on a high mountain plateau and moves out in all directions it is called an ice cap. When ice caps grow to cover whole islands or continents we call them ice sheets.
There are two big ice sheets in the world. In Greenland over 80% of the island is covered with ice and almost all of Antarctica has ice on it. In these places ice can grow to be 3,000 meters thick. Ice sheets continue to grow even if there is not a lot of snowfall. Sometimes ice sheets extend out into the oceans. Huge chunks of ice break off and turn into icebergs that float in the ocean
Since the 19th century scientists have learned a lot about how climate works and how it changes. Today we know that at times during the earth’s history there have been colder periods . During the last three million years there have been four Ice Ages that we know of. After each of these colder periods it became warmer and glaciers retreated. The last Ice Age probably ended about 10,000 years ago and today we are in an interglacial period.
Parts of the world covered with ice during the last Ice Age
- Climate Change Could Melt Himalayan Glaciers
- Geological History of the Earth
- Antarctic Ice on the Rise
- Iceberg Traps Antarctic Penguins
- at times = sometimes
- carve out = cut out of an object
- chunk = a large piece of something
- coastal = where the sea meets land
- completely =totally
- continue = to go on
- cover =to form a layer over something
- depend on =to be affected by something
- direction =path, route
- equator = the line around the middle of the earth
- extend =reach out into
- float = to swim on the sea
- flood = to cover land with water
- flow =move into
- form = start to exist
- freeze-froze-frozen = if an object is very cold and becomes hard
- freshwater = water that has no salt
- gigantic = very big
- in some cases = sometimes
- increase = to go up
- interglacial = between two Ice Ages
- layer =material that lies between two other parts
- length =how long something is
- melt =to become water
- moraine = the rocks that are moved along at the bottom of a glacier
- period = a time in history
- pile = more and more material is left there
- probably =likely, almost certainly
- range =a group of mountains
- reshape =to give another form
- retreat = to go back
- rock = hard objects that you can find on earth
- scientist =a person who is trained in science
- sea level =the average height of the sea; it is a standard which is used to measure how high mountains, cities and other objects are
- shape = form
- speed =how fast something is
- standstill = if something doesn’t move
- valley = the low land between two mountains
- weight =how heavy something is
- Earth Science
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- Earth Science
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Most of today’s landscapes were carved out by the extensive glaciers of the most recent ice age. The perfectly modified landscapes robustly reflect the handiwork of ice. This carving ability explains why they are known as nature’s bulldozers. Europe harbors most of the world’s glaciers. The largest glacier is eastern Antarctica’s Lambert Glacier, which is approximately 60 miles wide, more than 250 miles long and more than 8,000 feet thick. Glaciers form where snow builds up over time. It takes decades or centuries for glaciers to form.
A glacier by definition is a slow moving mass of ice. It mainly occurs in the high mountain valleys and colder Polar Regions. However, not all masses of ice qualify to be a glacier. To be called a glacier, ice must be at least six hundreds of a square mile in size and more than 164 feet in thickness. The chief raw material for glacial ice is snow. This means glaciers develop in regions where a lot of snow falls during winter than it melts in summer. The extremely low temperatures in these regions allow huge amounts of snow to pile up and transform into ice. Whenever this phenomenon happens each passing year, there is slow accumulation of snow. These areas where snow rests year in year out are called snowfields.
How do Glaciers Form?
A substantial amount of snow build up is needed for glacial ice to form. It’s paramount that snow accumulating during winter surpasses that which melts away in the summer, by far. Snowflakes are the hexagonal water crystals. However, you need to know that layers of fluffy snowflakes are not considered glacial ice yet.
As the accumulation of snow continues, the snowflakes buried underneath become a lot more firmly packed together. The tight packing triggers the snowflakes to assume round shapes while the hexagonal snowflake’s shape gets disintegrated. Over time, the well-rounded grains buried deep become heavily packed, driving out a lot of the air that’s imprisoned between the grains. The grainy shaped snow grains are referred to as firn and take about a year to form.
The dense, towering snowpark apply huge amount of pressure on the layers of firns under. This pressure causes the layers of firn to begin to melt slowly. The firn and meltwater gradually recrystallize to form glacial ice. This conversion process may well take years, decades or even centuries due to the fact that glacial ice formation is hugely pegged on the quantity of snowfall.
The weight of the glacier combined with the gravitational pressure might cause the ice occurring along the base of the glacier to start melting. Melting is enabled because the temperature required for ice to melt is minimized as a result of the pressure applied by the weight of the top glacial ice. When the ice melts, the glacier may start to move. Although glaciers are known to move slowly, some move fast, 100 feet per day to be specific. Glacier movement occurs in two ways; either retreating or advancing. However, these movements of glacier pretty much depend on where the cone-like nose is facing. The downhill movement of the glacier causes chopping and remolding of the landscape, which explains the gorgeous landscaping sceneries on mountains.
Types of Glaciers
They are similar to mountain ranges. They are bowl shaped and form high up in the mountains. As the glacier builds up in size, the ice below the towing glacier begins to melt, and is channeled into a valley.
These are large alpine glaciers that are confined to steep-walled valleys. They usually follow the path of an ancient river valley. They carry along rock debris they stumble across on the way or those that fall into them. The downhill movement of valley glaciers causes massive erosion, eventually carving the valley into a U shape, as opposed to V shape characteristically formed by early stages of river erosion.
A piedmont glacier comes about when a huge Alpine glacier slides to the bottom of the mountain range. While at the bottom of the mountain range, it can spread to become bigger than its valley source. They grow even bigger over time by constantly being fed by from alpine glaciers.
A Cirque is an amphitheatre-like valley carved out by glacial erosion. Cirque glaciers are bowl in shape on the mountain. The majority of Cirque glaciers are relatively small, less than one km across. As they fall downhill, they mix up with other glaciers to become a broader valley glacier.
These kinds of glaciers rise when Alpine glaciers plunge into the ocean. They later break off to form icebergs floating on the surface of the water.
An ice sheet is a relatively big, uncontrolled ice mass that flows downhill in every direction. A classic example of an ice sheet is the one found in Greenland.
An icecap is a domed shaped, unrestricted glacial mass. It’s capable of flowing in any direction. It can cover up an entire island or mountain range. When an ice cap goes beyond 50,000 square kilometers, it becomes an ice sheet.
Where are Glaciers Found (Location)?
Although a vast majority of glacial ice is located in Antarctica and Greenland. Glaciers are found all over the world, Africa including. Because specific geographic and climatic conditions must be present for glaciers to form, they are most prevalent above snowline. This means areas that experience high winter snow and cool summer temperatures form lots of glaciers.
This weather condition enables lots of snow to accumulate on the glacier during winter and will slightly melt during summer, which is why the majority of glaciers are situated in either Polar or mountainous regions. However, snow line can happen at diverse altitudes. For example, in Washington State, the snow line stands at 1600 meters. In Africa, it’s well over 5100 meters.
In Antarctica, snow line is at sea level. The quantity of snow that a glacier is able to convert into ice is critical to its survival. This explains why a cold place such as Siberia lacks a sizable amount of glaciers despite the right conditions. The reason is that there is absence of enough snow falls. The combined glaciers of the world cover more than 15,800,000 square kilometers. This represents an area almost the size of South America. The 5 longest glaciers in the world include:
The Lambert Glacier: Located in the Antarctica and measures about 515 kilometers long. It drains one-fifth of the Antarctica ice sheet every year. The Lambert Glacier feeds more than 35 km2 of ice to Prydz Bay every year.
The Novaya Zemlya Glacier: Located in the Arctic Ocean in northern Russia. It measures about 418 km in length.
The Arctic Institute Glacier: Located in the Antarctica and measures about 362 kms in length.
The Nimrod-Lennox-King Glacier: Located in the Antarctica. It measures about 290 kms in length
The Denman Glacier: Located in the Antarctica. Measures about 241 kms in length.
When most people think of the benefits of glaciers, their scenic value quickly pops to mind. On top of that, Glaciers bring more tangible benefits such as water for hydroelectric power production and irrigation. Also, sediments from glaciers contribute to underground water supplies. Meltwater from glacier is the purest water on earth. Most of it is harnessed to produce drinking water.
Photo by: girlart39
Presentation on theme: «Topic 2 – Earth’s Frozen Water What is a Glacier? Large bodies of moving mass of ice and snow are called glaciers. An ‘ Ice Cap ’ is a glacier that forms.»— Presentation transcript:
Topic 2 – Earth’s Frozen Water What is a Glacier? Large bodies of moving mass of ice and snow are called glaciers. An ‘ Ice Cap ’ is a glacier that forms on an extensive area of relatively level land that flows out from its source. An ’ icefield ‘ is an upland area of ice that feeds two or more glaciers. (The Columbia Icefield, in the Rocky Mountains, feeds 6 glaciers, is the source of three of Canada’s major rivers and replenishes three different oceans.) How Do Glaciers Form? All glaciers begin as snowflakes. These snowflakes accumulate, becoming grains, ice crystals and the weight of the snow creates pressure that gradually changes the ice crystals into glacial ice.
Valley Glaciers Glaciers form high in the mountains and move through valleys between mountain peaks. These are called valley glaciers. Continental Glaciers Those covering large areas of land are called continental glaciers or icecaps. Continental glaciers cover Antarctica and Greenland.
Glacial Features The shapes that develop in flowing ice are unique. Where a glacier flows over a steep cliff and breaks up, an icefall results. A crevasse is a fissure, or crack, in the ice. Glacial Movement The movement of glaciers depends on the climate. In colder climates, little melting occurs and the glacier continues to grow or move forward (this is called an advancing glacier). If the climate is warmer, the glacier melts faster than it grows and leaves the rocks, soil and large boulders it once contained. These glaciers are called retreating glaciers.
Pack Ice and Icebergs Pack ice is a sheet of ice that is rarely more than 5 meters thick that breaks easily. This usually happens in freezing sea water when large pieces break off as they move into warmer water. Icebergs are large chunks of ice that break loose, or calve, from continental glaciers as the glaciers flow into the ocean. These chunks are visible as they move through the ocean, melting faster below the surface than above.
How Glaciers Shape The Land Glacial Erosion As glaciers advance or retreat, they create specific glacial features across the landscape. Evidence of Valley Glaciers Valley glaciers carve (erode) bowl-shaped basins, called cirques in the sides of mountains. When two or more glaciers act on a mountain – eroding it from two different directions, a ridge forms, called an arête. If it forms a sharpened peak it is called a horn.
Glacial Deposition The collection of rocks, boulders, sand, clay and silt that is left behind as a glacier slows down and melts, is called till. Moraine Drumlin Esker Kettle Lakes Till
Outwash Plain Erratic “Big Rock” Okotoks
Meltwater Features Meltwater — water formed by the melting of snow and ice – carves channels in and throughout glaciers. A millwell is a rounded drain in the ice that is chiselled by a stream as it plunges downward. The Importance of Glaciers Icefields, glaciers, and snow – high up in the mountains – act as natural reservoirs, collecting snow in the cold months and releasing it as meltwater as it warms up. This meltwater helps run hydroelectric plants, irrigate crops, water cattle and supply drinking water. Glaciers slow the water cycle and provide important clues to understand historical climate patterns.
Ice Ages The Earth has had 7 major Ice Ages over the last several million years. During this time glaciers covered approx. 28% of the Earth’s surface. In the last Ice Age, Canada was completely covered by a continental glacier. At the peak of the Ice Age the average temperatures around the world were 5 o C colder than they are now. Ice Ages and Climate Change A small change in the average temperature is enough to start a chain of events that can produce an Ice Age. There might be reduced thermal energy from the Sun. There might be increased volcanic activity – adding clouds of ash into the atmosphere, thus reducing how much thermal energy from the Sun reaching Earth. Mountain building may cause more snow to accumulate and reflect sunlight – thus reducing the temperature. The movement of Earth’s tectonic plates alters the shape of the oceans and affects ocean currents, causing less mixing of hot and cold water. A change in the tilt of the Earth’s axis may also alter the temperature.
Climate Changes Today The greenhouse effect and global warming are two unrelated events that affect the average temperature on the Earth. The greenhouse effect is the natural warming of the Earth caused by gases in the Earth’s atmosphere trapping heat. Without it, life would not be able to survive. Global warming is the increase of these greenhouse gases, which causes more heat to be trapped and the temperature around the world increases – causing ice caps to melt producing widespread flooding.