An ice sheet is a mass of glacial land ice larger than 50,000 square kilometers. Earth has just two: one covering most of Greenland and one across Antarctica. As of November 2026, the Greenland Ice Sheet covers about 1.7 million square kilometers, 80 percent of Greenland, the world's largest island. That is about three times the size of Texas. The Antarctic Ice Sheet holds about 30 million cubic kilometers of ice, while the Greenland Ice Sheet holds about 2.9 million. An ice cap is a smaller, dome-shaped mass.

Ice sheets are not still. Near the top of an ice sheet, where the slope is shallowest, ice moves a few centimeters to a few meters per year. Near the coast, ice flowing into outlet glaciers can move hundreds of meters or even several kilometers per year. Ice shelves are floating sheets of ice that are connected to the land. Antarctica has 15 major ice shelf areas and many smaller ones. Most of the world's ice shelves fringe the Antarctic coast, and the largest are as big as Texas or France. Antarctic ice shelves can break off icebergs more than 80 kilometers (50 miles) long.

Sea ice is a different kind of ice. It is frozen seawater that floats on the ocean. As of November 2026, about 34 million square kilometers of the world's oceans, about 9 percent, have sea ice at some point in the year. That is about three times the area of Canada. In late winter Arctic sea ice covers on average about 15.5 million square kilometers and Antarctic sea ice about 18.5 million. By summer's end, Antarctic sea ice falls to about 2.5 million square kilometers, and Arctic sea ice to about 6.5 million (1981 to 2010 average).

Antarctic sea ice is typically 1 to 2 meters thick, while Arctic sea ice is typically 2 to 3 meters thick, as of November 2026. Arctic ice stays in the cold basin and piles into ridges as floes collide. Turn now to the land itself. The Transantarctic Mountains run across Antarctica and divide it into East and West. East Antarctica's ice is thicker and rests on rock that is mostly above the ocean surface. In the west the ice is thinner and much of the rock beneath it lies below the ocean surface. Less than 1 percent of Antarctica is free of ice.

The Arctic has two main climate types. Near the ocean the climate is maritime, with stormy, wet winters. Inland the climate is continental, drier, with winters that can be severe and summers that can be very warm. As of November 2026, permafrost covers about 23 million square kilometers, about 25 percent of the exposed land in the Northern Hemisphere. Far less has been found in the Southern Hemisphere, but some is in Antarctica, including the McMurdo Dry Valleys. Caribou make one of the world's great large-animal migrations. Some herds travel up to 800 miles to their summer grazing grounds, then turn back south when the first snow falls.

People have long lived in the Arctic. The Inuit of Canada and Greenland built snow houses, known as igloos, from stacked blocks of ice insulated with snow. Blocks were stacked in a spiral to make a dome, and an igloo could hold from two to 20 people. The Sami of northern Scandinavia and the Nenets of Russia's Arctic herd reindeer and use them for meat. Nunavut, Canada's largest territory, was created in 1999 after an agreement between the government of Canada and Inuit bands. As of November 2026, more than half of its people identify as Inuit, and Inuktitut is the most-spoken language. Antarctica, by contrast, has no native people.

Words to know

• outlet: way out
• floes: ice pieces
• permafrost: frozen ground
• maritime: near the sea