evidence: Mesas are flat-topped hills found in the American Southwest. They form over millions of years through a fascinating geological process. Wind and water erode the land around them, creating these iconic shapes. [...] The mesa’s flat top is thanks to a hard caprock. This layer, often sandstone or limestone, shields the softer layers beneath. As time goes on, the areas around the caprock erode, leaving the distinctive mesa shape. [...] Mesas are amazing geological wonders that have fascinated people for centuries. They are shaped by erosion over millions of years. These flat-topped hills and mountains are found in dry areas worldwide, especially in the American Southwest.