Ice capsare found in polar and subpolar areas of high mountain ranges with ice and snow on the peaks all through the year. Ice caps are smaller versions of ice sheets. They cover an area less than 50,000 square kilometers. Ice caps can be thousands of meters long and hundreds of meters deep. The mountain ranges of Alaska and Norway, as well as polar islands like Iceland, have ice-capped peaks. When an ice cap covers a single peak like Mount Rainier, it is called a carapace
ice cap.
When snow that falls on high mountain peaks and plateaus builds up year after year with little summer melt, an alpine ice fieldis formed. After the snow
An ice capis the area of ice that spreads out equally in all directions from the center of a glacier.
gets to be about 30 meters deep, the bottom layers become compressed into ice. Snow keeps falling on the mountains and the snow gets deeper. Eventually, the snow overflows nearby valleys and starts flowing downhill. When this happens, you have a glacier!
Canada has experienced four major Ice Ages. Of these, the Columbia Ice Field remains as part of a huge sheet of ice that originally covered nearly all of the Rocky Mountains. Though currently shrinking from global warming, the Columbia Ice Field’s glaciers once extended much farther south during the last Ice Age. This ice field includes nearly all the parts of an active ice field and gla- cier system.
The Columbia Ice Field, the largest body of ice in the Canadian Rocky Mountains, measures 325 km2in area and is estimated to be 365 meters thick.
Mount Columbia is the highest point in the ice field at 3745 meters. The aver- age snowfall on the Columbia Ice Field is about 7 meters per year. The Columbia Ice Field spread out during the last ice age and has three main outlets, including the Athabasca Glacier.
Ice sheets can be divided into two types: land-based ice sheets and marine- based ice sheets. The base of a land-based ice sheet lies mostly above sea level. The East Antarctic Ice Sheet and the Greenland Ice Sheet are land-based ice sheets.
Conversely, the greater part of the West Antarctic Ice Sheet lies below sea level. The West Antarctic Ice Sheet is a marine-based ice sheet. Much of the West Antarctic Ice Sheet is grounded well over a kilometer below sea level and more than two kilometers below sea level near its center. Its surface slope is less than that of the East Antarctic Ice Sheet. This sloping profile leads glaciologists to believe that the West Antarctic Ice Sheet is flowing and shrinking faster than its East Antarctic counterpart.
Acontinental ice sheetis the largest of the glacial masses. It builds up in the coldest regions with the most yearly snowfall. As the snow gets deeper and the base ice gets thicker, the ice sheet covers mountains and spreads over and across everything in its path. When a continental ice sheet comes to a valley, it
When an ice cap carves a valley and emerges at the lower end, it is called an outlet glacier.
An ice sheetor ice fieldis a thick layer of pressure-packed ice located on a high, nearly level area of land.
pours into it and fills it. Tall peaks are pushed up against and around shaping ice at the sheets’ edge to bend and melt forming streams. The longest glacier in North America is the Bering Glacier in Alaska, extending 204 km.
Greenland’s continental ice sheet, with ice over 125,000 years old, covers an area of over 1 million km2. This sheet is the largest glacier in the Northern
Hemisphere. It reaches a maximum thickness of nearly 3000 meters near the center of the island where it lies on the land’s surface. Near the coast, large masses of the glacier break off to form icebergs. Ice covers everything except coastal areas and the tops of some mountain peaks. These summits, sticking though the ice, are called nunataks. Narrow outlet glaciers drifting down from the northern continental ice sheet in Greenland drop over 10,000 icebergs into the Atlantic Ocean each year, some the size of office buildings.
Pack icedescribes the first ice formed on the surface of the sea. Exposed to different climatic conditions, it becomes broken, piled up, and packed together. Pack ice is constantly on the move, driven by the winds and ocean currents. Stress from the wind forms cracks in thinner ice, which the wind then widens. A large crack in the ice is called a lead.
During frigid winter months, the water in a lead will freeze again quickly. If the water is calm, it forms nilas.Nilas is a gray, greasy-looking ice that freezes into a thin, transparent ice layer filling the lead. Since it is so thin, the nilas is easily cracked again by the wind. New thin ice is also easily crushed by thicker floes to form a pressure ridge.
Pack ice presents a challenge to navigation. However, there are powerful ice- breaking ships that can slice a path through pack ice. Breaking ice is not just a matter of forcing ice out of the way, as you might think, but happens when a ship rides up onto and over the ice in front of it. Icebreakers are specially designed for this and have sloping bows, heavy displacement (weight) for their size, and lots of power. They are also specifically reinforced to handle the force of the ship hitting the ice at speed. Then, once the ship is on top of the ice, its huge weight (around 13,000 to 15,000 tons) breaks and crushes the ice beneath it. Countries and companies who trade in and around the northeast and northwest passages of the Arctic use icebreakers.