Glaciers are part of Earth's hydrologic cycle. A. Glaciers, which at present contain 80 percent of Earth's freshwater, form when accumulated snow is compressed and recrystallized into ice over a period of years. B. When there are glaciers on Earth, water is cycled through the glacier system, but the cycle period may be hundreds of thousands of years during periods of ice ages. C. The glacial system is governed by precipitation and temperature in such a way that glaciers cannot form in temperate latitudes. D. When glacial ice reaches a depth of 30 meters, the weight of the ice causes ice crystals at the bottom to flow, and the resulting movement of the glacier carves the landscape. E. If global warming melted the world's glaciers, sea level would rise about 60 meters worldwide. F. Glaciers have had little effect on Earth's surface because only 2 percent of Earth's water is currently contained in glaciers, and there are fewer glaciers now than at most times in the past.