This results in a fan-shaped deposits as the streams change flow around previously deposited material. A bajada is the coalescence of several alluvial fans. Alluvial fans are common in arid environments. As mesas are reduced by erosion they become buttes. Often a resistant layer, like sandstone, at the top protects less resistant layers below from erosion.
Buttes are common in the American southwest.
About 100 MYA this area was covered by an transgressive-regressive sea which deposited alternating layers of limestone. Some layers are more resistant than others. Harder deposits produce steeper, often cliff-like terrain, whereas softer layers produce slopes. Exfoliation domes are the result of erosion and uplift exposing batholiths. Batholiths are igneous intrusions formed beneath the earth's surface.