Due to its size and geologic features such as the Balcones Fault, Texas contains diverse landscapes common to both the U.S. Southern and the Southwestern regions. Although Texas is popularly associated with the U.S. southwestern deserts, less than ten percent of Texas's land area is desert. Most of the population centers are in areas of former prairies, grasslands, forests, and the coastline. Traveling from east to west, one can observe terrain that ranges from coastal swamps and piney woods, to rolling plains and rugged hills, and finally the desert and mountains of the Big Bend.