Southwestern Formation is a geological term used to describe the landforms found in the southwestern United States. It is characterized by flat-topped mesas, buttes, and canyons. The term 'mesa' is derived from the Spanish word for 'TABLE' and is a four-letter word that is often used to describe this type of formation. Mesas are formed when erosion wears away the softer sedimentary rocks, leaving behind the harder, more resistant rocks. This type of formation is common in the arid regions of the southwestern United States, where the climate is dry and the land is mostly flat.