We explored the ways that boulders and bedrock affect the shapes of hills and valleys by testing how quickly they erode compared to soil. We found that bedrock and boulders mostly erode more slowly than soil and predict that fracture patterns affect where they exist. We also found that streams generally follow fault orientations. Together, our data imply that fractures influence landscapes by weakening bedrock, causing it to erode faster and to eventually form a valley where a stream may flow.