The rock cycle is driven by two forces: (1) Earth's internal heat engine, which moves material around in the core and the mantle and leads to slow but significant changes within the crust, and (2) the hydrological cycle, which is the movement of water, ice, and air at the surface, and is powered by the sun.
The Fertile Crescent is bounded on the west by the Mediterranean Sea and on the East by the Persian Gulf. The Tigris and Euphrates rivers flow through the heart of the Fertile Crescent.
