Depth to Bedrock on Hillslopes (IMAGE) University of California - Berkeley Caption Weathered rock (light brown), an often thick layer of fractured rock underlying the thin veneer of soil (dark brown) and just above the impermeable bedrock (gray), can hold more water than soil and plays a major role in determining runoff, landslides and the evolution of mountainous or hilly terrain. Berkeley geologists argue that the rate at which water drains from bedrock (blue arrows) determines the thickness of weathered rock. Credit William Dietrich and Daniella Rempe, UC Berkeley Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.