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:

  1. mean annual temperatures are close to the freezing point
  2. winter precipitation produces significant accumulations of snow
  3. 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.

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Which mountain in the conterminous U.S. has the most glaciers?

Mount Rainier, Washington, at 14,410 feet (4,393 meters), the highest peak in the Cascade Range, is a dormant volcano whose glacier ice cover exceeds that of any other mountain in the conterminous United States. Mount Rainier has approximately 26 glaciers. It contains more than five times the glacier area of all the other Cascade volcanoes...

How long can we expect the present Interglacial period to last?

No one knows for sure. In the Devils Hole, Nevada, paleoclimate record, the last four interglacials lasted over ~20,000 years with the warmest portion being a relatively stable period of 10,000 to 15,000 years duration. This is consistent with what is seen in the Vostok ice core from Antarctica and several records of sea level high stands. These...

Are today's glaciers leftovers from the Pleistocene ice age?

Yes and no. It depends on which glaciers you are considering. Parts of the Antarctic Continent have had continuous glacier cover for perhaps as long as 20 million years. Other areas, such as valley glaciers of the Antarctic Peninsula and glaciers of the Transantarctic Mountains may date from the early Pleistocene. For Greenland, ice cores and...

How many glaciers currently exist in Alaska?

Based on the most recent comprehensive survey in 2011, there were about 27,000 glaciers in Alaska. However, the number of glaciers is a misleading statistic. Scientists are more interested in total glacial land coverage as a measure. The number of glaciers is less important since large ones can split up into several as they retreat. The amount of...

How old is glacier ice?

The age of the oldest glacier ice in Antarctica may approach 1,000,000 years old The age of the oldest glacier ice in Greenland is more than 100,000 years old The age of the oldest Alaskan glacier ice ever recovered (from a basin between Mt. Bona and Mt. Churchill) is about 30,000 years old. Glacier flow moves newly formed ice through the entire...

Was all of Alaska covered by glaciers during the Pleistocene Ice Age?

No--most of interior Alaska, south of the Brooks Range and north of the Alaska Range, was a non-glaciated grassland refuge habitat for a number of plant and animal species during the maximum Pleistocene glaciation. This ice-free corridor also provided one route for humans to move into North America.

Do ice worms exist?

Yes, ice worms do, in fact, exist! They are small worms that live in glacial ice in Alaska, Washington, Oregon, and British Columbia; they have not been found in glaciers elsewhere. Contrary to stories and songs, they do not give glacier ice its blue color and they don't grow to lengths of 50 feet. (These myths were made popular by poet Robert...

Is glacier ice a type of rock?

Yes – glacier ice, like granite, is a type of rock. Glacier ice is actually a mono-mineralic rock (a rock made of only one mineral, like limestone which is composed of the mineral calcite). The mineral ice is the crystalline form of water (H 2 O). It forms through the metamorphism of tens of thousands of individual snowflakes into crystals of...

Why is glacier ice blue?

Because the red (long wavelengths) part of white light is absorbed by ice and the blue (short wavelengths) light is transmitted and scattered. The longer the path light travels in ice, the more blue it appears.

How much of the Earth's water is stored in glaciers?

About 2.1% of all of Earth's water is frozen in glaciers. 97.2% is in the oceans and inland seas 2.1% is in glaciers 0.6% is in groundwater and soil moisture less than 1% is in the atmosphere less than 1% is in lakes and rivers less than 1% is in all living plants and animals. About three-quarters of Earth's freshwater is stored in glaciers...

Where are Earth’s glaciers located?

Glaciers exist on every continent except Australia. Approximate distribution is: 91% in Antarctica 8% in Greenland Less than 0.5% in North America (about 0.1% in Alaska) 0.2% in Asia Less than 0.1% is in South America, Europe, Africa, New Zealand, and Irian Jaya.

What are the impacts of glacier loss, other than losing an aesthetic landscape feature?

Glaciers act as reservoirs of water that persist through summer. Continual melt from glaciers contributes water to the ecosystem throughout dry months, creating perennial stream habitat and a water source for plants and animals. The cold runoff from glaciers also affects downstream water temperatures. Many aquatic species in mountainous...
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Date published: May 10, 2017

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.

Date published: September 28, 2016

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.

Date published: March 18, 2015

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.

Date published: December 4, 2014

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.

Date published: August 25, 2010

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.

Attribution: Land Resources
Date published: August 25, 2010

Glaciers Retreating in Asia

Many of Asia’s glaciers are retreating as a result of climate change.

Attribution: Land Resources
Date published: July 14, 2010

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.

Date published: August 10, 2009

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.

Date published: October 6, 2008

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.

Date published: May 29, 2002

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.

Date published: August 28, 1998

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.

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A glacier, with a lake below it.
December 31, 2018

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

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December 8, 2017

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 (

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October 5, 2017

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

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July 27, 2017

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.
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Monitoring glaciers in Glacier National Park.
April 5, 2016

Monitoring glaciers in Glacier National Park.

Monitoring glaciers in Glacier National Park.

Earth As Art image of glacier in Greenland
June 24, 2014

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

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Image: Getting the Shot, Grinnell Glacier, Glacier National Park.
January 1, 2010

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. 

video thumbnail: USGS Public Lecture Series: Baked Alaska--What's Happening to the Glaciers in Alaska?
September 1, 2009

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.

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Attribution:
Image: Surprise Glacier
August 22, 2008

Surprise Glacier

Surprise Glacier, Harriman Fiord, western Prince William Sound.

Image: Surprise Glacier
August 22, 2008

Surprise Glacier

Surprise Glacier (in background), Harriman Fiord, western Prince William Sound.

Image: Barry Glacier
August 20, 2008

Barry Glacier

Barry Glacier, Barry Arm, western Prince William Sound.

August 6, 2005

Bear Glacier

Oblique aerial photograph that shows the terminus of Bear Glacier, Kenai Mountains, Kenai Fjords National Park, Alaska.