Glaciers can be found in both polar and more temperate climates. They are the most abundant in the polar regions, where it remains so cold that only a minor amount of water is lost through melting or evaporation. They can also be found in the highest mountains in temperate or even tropical latitudes where temperatures remain cold throughout the year, such as in the Pacific Northwest of the United States and Canada, Alaska, and South America. More snow and ice accumulate during the winter months in these mountain ranges than is lost as meltwater in the summer.
About one‐tenth of the land surface on Earth is covered by glaciers today. Over 75 percent of this amount is on Antarctica, and 10 percent is on Greenland. The remainder occurs in mountain regions across the world. If the entire Antarctic ice sheet melted, it would raise the sea level about 60 meters (200 feet) and flood many cities in low‐lying coastal areas around the world.
Ice sheets are associated with continental glaciation and cover large areas of a landmass (over tens of thousands of square kilometers). Ice sheets exist in Greenland and Antarctica. Ice caps are similar to ice sheets but are much smaller—they are usually found in the highest part of a mountain range, where the snow accumulation is the greatest. An ice cap can be a source for multiple valley glaciers.
Valley glaciers (or alpine glaciers) are masses of ice that are restricted to high mountain valleys. As they move downslope, they can connect with larger valley glaciers. The majority of alpine glaciation is the result of the repeated advance and retreat of valley glaciers. Valley glaciers are common in the mountain ranges of the United States and Canada. Piedmont glaciers are the forwardmost extension of valley glaciers and form where the ice emerges at the front of the mountain range. The ice spreads out on the flat terrain to form a wide sheet at the mouth of the valley.