Erosion controlled by joints. Stronger bed forms a cap rock that holds up the arch. Some arches are almost 100 m long. Canyons are cut into the cuesta. The canyons sheltered Native American people from the harsh winter climate of the Plateau, and provided a year-around water source.
Rain seeps into the ground at the surface of the cuesta.
Then, the water percolates down through porous, permeable Mesa Verde sandstone. Until it reaches the underlying Mancos shale. These are pueblos. Population reached several thousand. Some pueblos had 200 rooms.