Concept

Ice cap

Summary
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Ice caps are not constrained by topographical features (i.e., they will lie over the top of mountains). By contrast, ice masses of similar size that are constrained by topographical features are known as ice fields. The dome of an ice cap is usually centred on the highest point of a massif. Ice flows away from this high point (the ice divide) towards the ice cap's periphery. Ice caps have significant effects on the geomorphology of the area that they occupy. Plastic moulding, gouging and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. On Earth, there are about of total ice mass. The average temperature of an ice mass ranges between . The core of an ice cap exhibits a constant temperature that ranges between . Ice caps are formed when snow is deposited during the cold season but doesn’t completely melt during the hot season. Over time, the snow builds up and becomes dense, well-bonded snow known as perennial firn. Finally, the air passages between snow particles close off and it transforms into ice. The shape of an ice cap is determined by the landscape it lies on, as melting patterns can vary with terrain. For example, the lower portions of an ice cap are forced to flow outwards under the weight of the entire ice cap and will follow the downwards slopes of the land. Ice caps have been used as indicators of global warming, as increasing temperatures cause ice caps to melt and lose mass faster than they accumulate mass. Ice cap size can be monitored through different remote-sensing methods such as aircraft and satellite data. Ice caps accumulate snow on their upper surfaces, and ablate snow on their lower surfaces. An ice cap in equilibrium accumulates and ablates snow at the same rate.
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