water cycle

The water cycle describes how water evaporates from the surface of the earth, rises into the atmosphere, cools and condenses into rain or snow in clouds, and falls again to the surface as precipitation.

Sun's heat causes glaciers and snow to melt into liquid water. This water goes into oceans, lakes and streams. Evaporation occurs when liquid water on Earth's surface turns into water vapor in our atmosphere.

The water cycle has no starting point. But, we'll begin in the oceans, since that is where most of Earth's water exists. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air.

Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff. ... Over time, though, all of this water keeps moving, some to reenter the ocean, where the water cycle "ends" and it "begins."