Earth’s water is always in movement, and the global water cycle describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening both rapidly and over millions of years. Explore the Water Cycle Interactive with Dr. David Yoxtheimer, Assistant Research Professor at the Earth and Environmental Systems Institute at Penn State University, to explore the major components of the global water cycle.