Although they've been on the retreat since Earth's last ice age, glaciers still have the power to amaze. These frozen masses of ice cover 10 percent of Earth's land area, appearing on every continent, even Africa, according to the National Snow and Ice Data Center (NSIDC). Here are a few notables. (Above, glacial ice at Parque Nacional los Glaciares in Argentina.)
The largest and longest glacier in Europe snakes among mountain peaks like a river frozen in time. Glaciers form when layers of snow build upon one another year after year. Eventually, the lower layers re-crystallize into ice. Tiny air bubbles in the ice preserve bits of ancient atmosphere, making glaciers an important research tool for scientists looking to understand the climate of thousands of years ago.
Snow-covered glaciers on the summit of Mount Kilimanjaro in Tanzania. Unfortunately, Kilimanjaro glaciers are retreating rapidly in recent years, according to research published in November 2009 in the journal Proceedings of the National Academy of Sciences. Between 1912 and 1953, the mountain's ice cover shrank by about 1 percent each year. Between 1989 and 2007, that rate increased to 2.5 percent per year.
The Briksdal Glacier in Norway. According to NSIDC, glacial ice gets its blue color when it becomes very dense. White-colored glacial ice has many tiny air bubbles embedded amidst its ice crystals. As the ice becomes dense, those air bubbles get forced out. The ice that is left behind absorbs all colors in the ice spectrum except blue.
An ice cave or englacial melt channel. This ice cave was formed by meltwater flowing within the glacier ice. Belcher Glacier, Devon Island, Nunavut, Canada.
A mountain-climbing expedition makes camp on a glacier on the slopes of Mount Elbrus, an inactive volcano in the Caucasus mountains of Russia.
Iceland is known for its glaciers with tongue-twisting names. Breiðamerkurjökull is in the southeastern part of the country.
Breiðamerkurjökull terminates at Jökulsárlón, the largest glacial lagoon in Iceland. The glacier expanded between the 1600s and the 1900s, during a cold period known as "The Little Ice Age." Warming temperatures since sent the glacier into retreat. Starting in about 1935, Jökulsárlón began to form in its wake. The glacial lagoon is now about 650 feet (200 meters) deep where the glacier's nose once was.
Fog crosses Hailuoguo glacier on Mount Gongga in the Sichuan province of China.
An aerial view of the Kennicott and Rott glaciers in the Wrangell Mountains of Alaska. Most of the United States' glaciers are located in Alaska.
The largest glacier in North America is Alaska's Bering Glacier, which currently terminates in the Vitus Lake about 6 miles (10 km) from the Gulf of Alaska.
The retreat of the Bering glacier, which has been ongoing since 1900, has the side effect of increasing the number of earthquakes in the area. The weight of the glacier once stabilized the boundary between the Pacific and North American tectonic plates, which meet along the Alaska coast. As the ice retreated, that compression disappeared, enabling the two plates to move against one another more freely.
Meltwaters flow from the Trift glacier in the Swiss alps.
Even Indonesia has glaciers — for now, at least. The ice fields of Puncak Jaya in Papua, Indonesia are, like other glaciers worldwide, shrinking
The Viedma, Agassiz, and Onelli glaciers are visible on this International Space Station photograph of Argentine Patagonia.
A web of cracks in meltwater ice found along the edge of Byrd Glacier in Antarctica. The 85 mile ( 137 kilometers) long glacier flows into the Ross Ice Shelf. About the size of France, the Ross Ice Shelf is the largest ice field in Antartica.
A grotto in an iceberg, photographed during the British Antarctic Expedition of 1911-1913. Photographer Herbert Ponting snapped this photograph in January 1911.
NOAA researchers took this picture of an enormous glacier while flying over the Antarctic landscape to McMurdo Station.
A natural glacial arch at Norsel Point on Anvers Island, Antarctica.
Almost a century ago, Antarctic explorers were awed by the natural ice sculptures they found on the continent. Frank Hurley took this photograph during Ernest Shackleton's "Endurance" Expedition in 1915. The expedition ship became trapped in sea ice during the voyage, forcing the crew to camp on ice for five months. Shackleton and a few crew members eventually took a lifeboat to South Georgia Island for help, a treacherous open-ocean journey that paid off when he was able to rescue all of his men.
Crevasses in the Guyot glacier near Ice Bay, Alaska.
The Aletsch Glacier of Switzerland is the largest in the Alps, but scour marks on the valley reveal that the ice used to extend much higher.
The ice of Argentina's Upsala Glacier appears almost neon blue.
A small valley glacier exiting the Devon Island Ice Cap in Nunavut, Canada.
Argentina's Upsala Glacier in Los Glaciares National Park has experienced rapid retreat.
Argentina's Perito Moreno Glacier is the third-largest reservoir of freshwater in the world.
The cracks and crevices of Argentina's Perito Moreno Glacier illustrate the slow movement of the ice.
Researchers dig a 13-foot (4 meter) pit into the snow of the Devon Island Ice Cap in Nunavut, Canada to examine annual snow layers.
A time-lapse camera keeps an eye on Nunavut, Canada's Belcher Glacier. Ground observations help researchers understand how much ice is calving into the ocean.
An aerial view of Nunavut, Canada's Sverdrup Glacier, which flows from the Devon Island Ice Cap to the ocean.
Meltwater ponded at the Columbia Glacier in Alaska, as seen in July 2008.
Crevasses in the accumulation zone of the Columbia Glacier in Alaska. The accumulation zone is the area of the glacier where snow accumulates and packs into ice.
Peripheral glaciers and ice caps in eastern Greenland. In the background, the ice sheet is visible, with glacier fingers protruding.
The terminus of Alaska's Columbia Glacier. The glacier retreated 8.7 miles (14 km) between 1984 and 2004.
A stranded iceberg from the Columbia Glacier in Prince William Sound, Alaska.