An official website of the United States government. Here's how you knowHere's how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Latest Earthquake | Chat Share
Glaciers are a big item when we talk about the world's water supply. Almost 10 percent of the world's land mass is currently covered with glaciers, mostly in places like Greenland and Antarctica. You can think of a glacier as a frozen river, and like rivers, they "flow" downhill, erode the landscape, and move water along in the Earth's water cycle.
• Water Science School HOME • Surface Water topics • Water Basics topics •
Even though you've maybe never seen a glacier or massive extents of ice, they are a big item when we talk about the world's water supply. Almost 10 percent of the world's land mass is currently covered with glaciers and ice caps, mostly in places like Greenland and Antarctica. Glaciers are important features in Earth's water cycle and affect the volume, variability, and water quality of runoff in areas where they occur.
In a way, glaciers are just frozen rivers of ice flowing downhill. Glaciers begin life as snowflakes. When the snowfall in an area far exceeds the melting that occurs during summer, glaciers start to form. The weight of the accumulated snow compresses the fallen snow into ice. These "rivers" of ice are tremendously heavy, and if they are on land that has a downhill slope the whole ice patch starts to slowly grind its way downhill. These glaciers can vary greatly in size, from a football-field sized patch to an ice patch a hundred miles (161 kilometers) long.
Glaciers have had a profound effect on the topography (lay of the land) in some areas, as in the northern U.S. You can imagine how a trillion-ton ice cube can rearrange the landscape as it slowly grinds its way overland. In this picture you can see the bowl-shaped valley in a glacial valley in Wyoming where an ancient glacier forced its way through the landscape. Many lakes, such as the Great Lakes, and valleys have been carved out by ancient glaciers. A massive icecap can be found in Greenland, where practically the whole country is covered with ice (shouldn't it be called Whiteland)? The ice on Greenland approaches two miles (3.2 kilometers) in thickness in some places and is so heavy that some of the land has been compressed so much that it is way below sea level.
Here's a map of where glaciers and icecaps exist in the world. White areas show glaciers and ice sheets around the world. The white spots in the oceans are islands where glaciers are found.
There are many long-term weather patterns that the Earth goes through. The climate, on a global scale, is always changing, although usually not at a rate fast enough for people to notice. There have been many warm periods, such as when the dinosaurs lived and many cold periods, such as the last ice age of about 20,000 years ago. During the last ice age much of the northern hemisphere was covered in ice and glaciers, and, as this map of Europe shows.
Glaciers are still around today; tens of thousands of them are in Alaska. Climatic factors still affect them today and during the current warmer climate today, they can retreat in size at a rate easily measured on a yearly scale.
►► Facts and myths about glaciers
Do you really like glaciers?
If so, vote for your favorite water body in our Activity Center!
Sources and more information
Activity icon made by Eucalyp from www.flaticon.com
Learn more about glaciers, icecaps, and related topics.
Pictures about glaciers and ice:
Publications about glaciers and ice caps:
Below is a list of Frequently Asked Questions associated with glaciers and ice caps.
A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity. Typically, glaciers exist and may even form in areas where:mean annual temperatures are close to the freezing pointwinter precipitation produces significant accumulations of snowtemperatures...
There is still some uncertainty about the full volume of glaciers and ice caps on Earth, but if all of them were to melt, global sea level would rise approximately 70 meters (approximately 230 feet), flooding every coastal city on the planet.Learn more:USGS Water Science School: Glaciers and IcecapsNational Snow and Ice Data Center: Facts about GlaciersU.S. Global Change Research Program: Sea...
Repeat photography and aerial / satellite photo analysis provide evidence of glacier loss in terms of shape and area. The USGS Benchmark Glacier project has collected mass balance data on a network of glaciers in Alaska, Washington, and Montana for decades, quantifying trends of mass loss at all sites. Extensive field data collection at these sites includes twice yearly visits to measure seasonal...
About 2.1% of all of Earth's water is frozen in glaciers.97.2% is in the oceans and inland seas2.1% is in glaciers0.6% is in groundwater and soil moistureless than 1% is in the atmosphereless than 1% is in lakes and riversless than 1% is in all living plants and animals.About three-quarters of Earth's freshwater is stored in glaciers. Therefore, glacier ice is the second largest reservoir of water...