Most lakes are fated to disappear over time. They can fill up with silt from the surrounding environment through rainfall, wind, or river deposits.
Because water is always seeking a lower base, lakes may be drained by water seeping into the land. Great geological events can make lakes disappear, such as the destruction of a huge ice dam in Montana 15,000 years ago.
Once the ice dam broke, the waters of the great Lake Missoula flooded the land and made its way to the ocean. Lakes may dry up through decreased precipitation and increased evaporation. The formation of new rivers can channel lake water away from its basin.
The destruction of lakes is not as dire as it sounds, however, because new lakes can be formed just as well. Almost everything that destroys a lake can also create one. Silt deposits can dam up rivers to form lakes. Drained lake water can form underground lakes or reemerge miles away.
Geological activity creates lakes by filling up volcanic craters with water, or creating basins through earthquakes that are later filled by rain, groundwater, or melting glaciers.
If the rate of precipitation outstrips evaporation, a lake may form. And rivers can run into obstacles that prevent them from continuing, so they pool up into lakes.