What is a glacier?
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 point
- winter precipitation produces significant accumulations of snow
- temperatures throughout the rest of the year do not result in the complete loss of the previous winter’s snow accumulation
Over multiple decades this continuing accumulation of snow results in the presence of a large enough mass of snow for the metamorphism from snow to glacier ice process to begin. Glaciers are classified by their size (i.e. ice sheet, ice cap, valley glacier, cirque glacier), location, and thermal regime (i.e., polar vs. temperate). Glaciers are sensitive indicators of changing climate.
Learn more: USGS Water Science School: Glaciers and Icecaps
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Which mountain in the conterminous U.S. has the most glaciers?
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How old is glacier ice?
Was all of Alaska covered by glaciers during the Pleistocene Ice Age?
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Glaciers Rapidly Shrinking and Disappearing: 50 Years of Glacier Change in Montana
The warming climate has dramatically reduced the size of 39 glaciers in Montana since 1966, some by as much as 85 percent, according to data released by the U.S. Geological Survey and Portland State University.
EarthView–As Glaciers Worldwide Are Retreating, One Defies the Trend
In this Landsat EarthView, one glacier in Chile bucks the global trend:
Fifty Years of Glacier Change Research in Alaska
ANCHORAGE, Alaska — This year marks the 50th anniversary of one of the longest continuous glacier research efforts in North America.
From Icefield to Ocean - What Glacier Change Might Mean for the Future of Alaska
Frozen bodies of ice cover nearly 10 percent of the state of Alaska, but the influence of glaciers on the environment, tourism, fisheries, hydropower, and other important Alaska resources is rarely discussed.
Rare Insect Found Only in Glacier National Park Imperiled by Melting Glaciers
The persistence of an already rare aquatic insect, the western glacier stonefly, is being imperiled by the loss of glaciers and increased stream temperatures due to climate warming in mountain ecosystems, according to a new study released in Freshwater Science.
Washington’s Benchmark Glacier Still Shrinking
TACOMA, Wash. — Washington’s only “benchmark” glacier continues to lose mass as a result of changes in climate, according to a report by the U.S. Geological Survey.
Glaciers Retreating in Asia
Many of Asia’s glaciers are retreating as a result of climate change.
Footloose Glaciers Crack Up
Glaciers that lose their footing on the seafloor and begin floating behave very erratically, according to a new study published in the journal Geophysical Research Letters. Floating glaciers produce larger icebergs than their grounded cousins and do so at unpredictable intervals.
Salazar Releases Long-Term Report Detailing Glaciers Shrinking in Alaska and Washington
A report on long-term glacier measurements released today by Secretary of the Interior Ken Salazar shows that glaciers are dramatically changing in mass, length and thickness as a result of climate change.
Most Alaskan Glaciers Retreating, Thinning, and Stagnating, Says Major USGS Report
Most glaciers in every mountain range and island group in Alaska are experiencing significant retreat, thinning or stagnation, especially glaciers at lower elevations, according to a new book published by the U.S. Geological Survey. In places, these changes began as early as the middle of the 18th century.
Decline of World's Glaciers Expected to Have Global Impacts Over This Century
The great majority of the world’s glaciers appear to be declining at rates equal to or greater than long-established trends, according to early results from a joint NASA and United States Geological Survey (USGS) project designed to provide a global assessment of glaciers. At the same time, a small minority of glaciers are advancing.
Alaskan Glaciers Yield Massive Floods
Torrents of meltwater are unleashed suddenly from the margins of the great moving sheets of snow and ice, known as glaciers. In Alaska, these pulses of activity, called "outburst floods," are usually caused by the failure of ice dams that restrain the meltwater of glacial margin lakes.
Endpoint of Mendenhall Glacier, Juneau, United States.
Glaciers: "Rivers" of Frozen Water
Even though you've maybe never seen a glacier, 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, mostly in places like Greenland and Antarctica. Glaciers are important features in the hydrologic cycle and affect the volume
...Image of the Week - New Rift on Greenland's Petermann Glacier
A new rift is forming across the Petermann Glacier. If this rift connects to existing rifts, it could result in another large iceberg breaking free.
At the USGS EROS Center, we study land change, operate the Landsat satellites, and maintain the longest, continuously acquired collection of images of the Earth's land surface.
USGS EROS Center (
Image of the Week - Pine Island Glacier’s Newest Iceberg
These Landsat 8 images show the latest iceberg to break free in Antarctica's Pine Island. Warmer ocean waters are melting the ice from beneath, causing increasing instability.
At the USGS EROS Center, we study land change, operate the Landsat satellites, and maintain the longest, continuously acquired collection of images of the Earth's land surface.
USGS
USGS Public Lecture: Warm Ice—Dynamics of Rapidly Changing Glaciers
- Glacier Numerology – The how big, how long, how thick, how much, how often, of glacier science.
- Glacier Photography – While a picture may be worth a thousand words, a collection of images may tell a complete forensic story.
- Glacier Geophysics – How new technologies are being introduced to reexamine and refine decades old glacier analyses.
Monitoring glaciers in Glacier National Park.
Monitoring glaciers in Glacier National Park.
Petermann Glacier
Located on the northwestern coast of Greenland, Petermann Glacier covers 1,295 square kilometers (500 square miles). The glacier's floating tongue of ice extends from the lower right corner of the image toward the top center. At 15–20 kilometers (9–12 miles) wide and 70 kilometers (43 miles) long, it is the longest floating glacier in the Northern Hemisphere. Infrared
...Getting the Shot, Grinnell Glacier, Glacier National Park.
USGS scientist shoots a repeat photograph of Grinnell Glacier in Glacier National Park to illustrate glacial recession due to impacts of climate change.
*note – logo on scientists hat is logo from USGS Northern Rocky Mountain Science Center, not private.
USGS Public Lecture Series: Baked Alaska--What's Happening to the Glaciers in Alaska?
Glaciers are Earth's largest reservoir of freshwater. As they change, so does global sea level. Alaska has one of the largest accumulations of glaciers anywhere on Earth outside of the Polar regions. For most of the past half century, Alaska has experienced a significant increase in temperature that has profoundly impacted its glaciers. Join USGS scientist Dr. Bruce F.
Surprise Glacier
Surprise Glacier (in background), Harriman Fiord, western Prince William Sound.
Bear Glacier
Oblique aerial photograph that shows the terminus of Bear Glacier, Kenai Mountains, Kenai Fjords National Park, Alaska.