How does present glacier extent and sea level compare to the extent of glaciers and global sea level during the Last Glacial Maximum (LGM)?

The Last Glacial Maximum (LGM) occurred about 20,000 years ago, during the last phase of the Pleistocene epoch. At that time, global sea level was more than 400 feet lower than it is today, and glaciers covered approximately:

  • 8% of Earth’s surface
  • 25% of Earth’s land area
  • 33% of Alaska

Beginning about 15,000 years ago, continental glaciers retreated and sea level began to rise. Sea level reached its current height about 8,000 years ago and has fluctuated ever since.

Today, glaciers cover approximately:

  • 3% of Earth’s surface
  • 11% of Earth’s land area
  • 5% of Alaska.

Learn more: USGS Water Science School - Glaciers: Things to Know 

Related Content

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Does the USGS monitor global warming?

Not specifically. Our charge is to understand characteristics of the Earth, especially the Earth's surface, that affect our Nation's land, water, and biological resources. That includes quite a bit of environmental monitoring. Other agencies, especially NOAA and NASA, are specifically funded to monitor global temperature and atmospheric phenomena...

What is the difference between global warming and climate change?

Although people tend to use these terms interchangeably, global warming is just one aspect of climate change. “Global warming” refers to the rise in global temperatures due mainly to the increasing concentrations of greenhouse gases in the atmosphere. “Climate change” refers to the increasing changes in the measures of climate over a long period...

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...

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. Learn more: USGS Water Science School - Glaciers...

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...

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 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...

How would sea level change if all glaciers melted?

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 Icecaps National Snow and Ice Data Center: Facts about...

How do we know glaciers are shrinking?

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...
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Date published: February 21, 2018

New USGS-Led Study Could Help Pacific Wetlands Adapt to Sea Level Rise

SAN FRANCISCO BAY, Calif. — A new study published Wednesday in Science Advances introduces an innovative tool to help resource managers preserve Pacific coastal wetlands from rising sea levels.

Date published: May 18, 2017

In Next Decades, Frequency of Coastal Flooding Will Double Globally

The frequency and severity of coastal flooding throughout the world will increase rapidly and eventually double in frequency over the coming decades even with only moderate amounts of sea level rise, according to a new study released today in “Scientific Reports.”

Date published: March 27, 2017

Disappearing Beaches: Modeling Shoreline Change in Southern California

Using a newly-developed computer model called “CoSMoS-COAST” (Coastal Storm Modeling System – Coastal One-line Assimilated Simulation Tool) scientists predict that with limited human intervention, 31 to 67 percent of Southern California beaches may become completely eroded (up to existing coastal infrastructure or sea-cliffs) by the year 2100 under scenarios of sea-level rise of one to two meters.

Date published: October 3, 2016

Rising Sea Levels, Coastal Development’s Effect on Gulf Coast Wetlands

As coastal development along the Gulf Coast continues to expand, tidal saline wetlands could have difficulty adjusting to rising sea levels.

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: July 12, 2016

Cape Cod susceptible to potential effects of sea-level rise

New USGS study highlights Cape Cod's risk to rising sea levels

Date published: October 1, 2015

Many Atolls May be Uninhabitable Within Decades Due to Climate Change

SANTA CRUZ, Calif. — A new study shows that the combined effect of storm-induced wave-driven flooding and sea level rise on island atolls may be more severe and happen sooner than previous estimates of inundation predicted by passive “bathtub” modeling for low-lying atoll islands, and especially at higher sea levels forecasted for the future due to climate change.

Date published: August 27, 2015

New Sea-Level Rise Handbook for Non-Scientists

Coastal managers and planners now have access to a new U.S. Geological Survey handbook that, for the first time, comprehensively describes the various models used to study and predict sea-level rise and its potential impacts on coasts.

Date published: August 14, 2015

Study Shows Sea Level Rise to Threaten West Coast Tidal Wetlands Over the Next 100 Years

The U.S. Geological Survey and Oregon State University released a report this week examining Pacific Northwest tidal wetland vulnerability to sea level rise. Scientists found that, while vulnerability varies from marsh to marsh, most wetlands would likely be resilient to rising sea levels over the next 50-70 years.

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: June 24, 2012

Sea Level Rise Accelerating in U.S. Atlantic Coast

Rates of sea level rise are increasing three-to-four times faster along portions of the U.S. Atlantic Coast than globally, according to a new U.S. Geological Survey report published in Nature Climate Change. 

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Glacier off Sargent Icefield
December 31, 2017

Glacier off Sargent Icefield

Landscape view of an un-named glacier off the Sargent Icefield, directly across from Wolverine Glacier, above the Nellie Juan River, in Alaska. Taken during a visit to a wolverine glacier field site as part of a study to examine how alpine areas are changing as temperatures rise in Alaska. 

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.
March 24, 2016

Marine Terraces of California: Landscapes from the Waves

  • Did you know soils on California’s marine terraces can be over a million years old? 
  • Have you wondered why California’s rugged shorelines are terraced?
  • Soils on marine terraces aid our understanding of soil formation, water movement, and carbon transformations under changing climate.
September 30, 2010

PubTalk 9/2010 — Great Missoula & Ice Age Floods Natl. Geologic Trail

- a journey through the landscape of Earth's greatest floods

by Richard Waitt, Geologist


  • Glacial Lake Missoula released scores of cataclysmic floods, sculpting the bizarre landscape of Washington's Channeled Scabland
  • New video depicts the enormous 3-day flood releasing 500 cubic miles of water
video thumbnail: USGS Public Lecture Series: Climate Change 101
August 24, 2009

USGS Public Lecture Series: Climate Change 101

Climate change is an issue of increasing public concern because of its potential effects on land, water, and biological resources. In the next several years, the United States will be challenged to make management and policy decisions as well as develop adaptation and mitigation strategies that will require anticipating the effects of a changing climate and its impacts on

Sea terrace at Año Nuevo Point, California
June 19, 2008

Sea terrace at Año Nuevo Point, California

Marine terrace dated to ~80,000 years by U-series methods on corals, overlain by eolian sand (Muhs, D.R., Simmons, K.R., Kennedy, G.L., Ludwig, K.R., and Groves, L.T., 2006, A cool eastern Pacific Ocean at the close of the last interglacial complex: Quaternary Science Reviews, v. 25, p. 235-262).

image of sea level rise animation
November 30, 2000

Sea Level Rise Animation - New York

Sea Level Rise Animation

World map showing location of major ice bodies and estimated sea level rise contributed by their melting
November 30, 2000

World map showing location of major ice bodies and estimated sea level

When past sea levels were higher, where did the water come from? Here are the possibilities, with the amount of sea level rise they could provide now.

Last-interglacial sea level as determined by dated corals

Last-interglacial sea level as determined by dated corals

Elevations of corals we have dated from last-interglacial marine deposits on tectonically stable coastlines indicate a paleo-sea level of +5 meters to +10 meters.

Washington D.C. with a 12 meters higher sea level

Washington D.C. with a 12 meters higher sea level

What would Washington D.C. look like with a sea level 12 meters higher? Some studies have suggested that 400,000 years ago, sea level could have been even higher than during the last interglacial (12 meters or more above present).

National Parks that could be threatened by higher sea level

National Parks that could be threatened by higher sea level

National Parks and Seashores on coasts that could be affected by future sea level rise.