Facts about glaciers

Photograph of blue glacier iceCalved off a glacier, the thick, clear ice in this iceberg radiates an ethereal blue color. Coarse ice crystals, and few bubbles or particles in the ice to scatter light, allow the light to penetrate deep into the surface before reflecting back. This increases the tendency for ice to slightly absorb red and infrared light to impart the blue tint. —Credit: Richard Droker

Presently, 10 percent of land area on Earth is covered with glacial ice, including glaciers, ice caps, and the ice sheets of Greenland and Antarctica. Glacierized areas cover over 15 million square kilometers (5.8 million square miles).

Glaciers store about 75 percent of the world's freshwater.

During the maximum point of the last ice age, glaciers covered about 32 percent of the total land area.

From the 17th century to the late 19th century, the world experienced a “Little Ice Age,” when temperatures were consistently cool enough for glaciers to advance in many areas of the world.

In the United States, glaciers cover over 75,000 square kilometers (30,000 square miles), with most of the glaciers located in Alaska.

If all land ice melted, sea level would rise approximately 70 meters (230 feet) worldwide.

Satellite image of Bering Glacier, AlaskaThis Landsat satellite image shows Bering Glacier in Alaska, the largest glacier in North America. Although the glacier has been retreating and thinning recently, it still surges about every 20 years or so. —Credit: NASA image by Robert Simmon, based on data provided by the Landsat 7 Science Team

Glacier ice crystals can grow to be as large as baseballs.

Glacial ice often appears blue when it has become very dense. Years of compression gradually make the ice denser over time, forcing out the tiny air pockets between crystals. When glacier ice becomes extremely dense, the ice absorbs a small amount of red light, leaving a bluish tint in the reflected light, which is what we see. When glacier ice is white, that usually means that there are many tiny air bubbles still in the ice.

North America's longest glacier is the Bering Glacier in Alaska, measuring 190 kilometers (118 miles) long.

The Kutiah Glacier in Pakistan holds the record for the fastest glacial surge. In 1953, it raced more than 12 kilometers (7.5 miles) in three months, averaging about 112 meters (367 feet) per day.

Satellite image of a large iceberg calving off the Larsen Ice Shelf in AntarcticaSatellite images caught this large iceberg, named A54, calving off of what remains of the Larsen Ice Shelf in Antarctica. Scientists installed research equipment on the smaller AMIGOSberg to study how icebergs melt. —Credit: Images courtesy of Terry Haran, National Snow and Ice Data Center, using data from NASA MODIS.

In Washington State, the state with the largest area of glaciers in the contiguous United States, melting glaciers provide 1.8 trillion liters (470 billion gallons) of water each summer.

The largest glacier in the world is the Lambert-Fisher Glacier in Antarctica. At 400 kilometers (250 miles) long, and up to 100 kilometers (60 miles) wide, this ice stream alone drains about 8 percent of the Antarctic Ice Sheet.

Antarctic ice is up to 4.7 kilometers (3 miles) thick in some areas.

Antarctic ice shelves may calve icebergs that are over 80 kilometers (50 miles) long.

The Antarctic continent has been at least partially covered by an ice sheet for the past 40 million years.

The land underneath parts of the West Antarctic Ice Sheet may be up to 2.5 kilometers (1.6 miles) below sea level.