When precipitation falls in very cold areas-at high elevations or high latitudes-the water may not immediately soak in, run off, or evaporate. Instead, it may become part of a snowfie glacier. In this way, glaciers store large quantities of on land. If present-day glaciers were to melt and release all their water, sea level would rise by several dozen meters. This would submerge many heavily populated coastal areas. As you will see in Chapter 6, over the past 2 million years, huge ice sheets have formed and melted on several occasions, each time changing the balance of the hydrologic cycle.