Glacier - a large, slow-moving mass of ice, formed from compacted layers of snow, that slowly flows in response to gravity and high pressure. The word glacier comes from Latin glacies meaning ice. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water. Glaciers cover vast areas of polar regions, and are found in mountain ranges of every continent, and are restricted to the highest mountains in the tropics. Glaciers are sensitive monitors of climate conditions and are crucial to both world water resources and sea level variation.
Permafrost - soil that remains frozen all year and has been frozen for at least two consecutive years. About 20 percent of Earth's landmass is covered by permafrost, which is generally 2-12 feet thick.