The vast majority of North America is on the North American Plate. Parts of California and western Mexico form the partial edge of the Pacific Plate, with the two plates meeting along the San Andreas fault. The southern-most portion of the continent and much of the West Indies lie on the Caribbean Plate, while the Juan de Fuca and Cocos Plates border the North American Plate on its western frontier. The continent can be divided into four great regions (each of which contains many sub-regions): the Great Plains stretching from the Gulf of Mexico to the Canadian Arctic; the geologically young, mountainous west, including the Rocky Mountains, the Great Basin, California and Alaska; the raised but relatively flat plateau of the Canadian Shield in the northeast; and the varied eastern region, which includes the Appalachian Mountains, the coastal plain along the Atlantic seaboard, and the Florida peninsula. Mexico, with its long plateaus and cordilleras, falls largely in the western region, although the eastern coastal plain does extend south along the Gulf. The western mountains are split in the middle, into the main range of the Rockies and the coast ranges in California, Oregon, Washington, and British Columbia with the Great Basin—a lower area containing smaller ranges and low-lying deserts—in between. The highest peak is Denali in Alaska. The United States Geographical Survey states that the geographic center of North America is "6 miles west of Balta, Pierce County, North Dakota" at approximately 48°10′N 100°10′W, approximately 15 miles (25 km) from Rugby, North Dakota. The USGS further states that “No marked or monumented point has been established by any government agency as the geographic center of either the 50 States, the conterminous United States, or the North American continent.” Nonetheless, there is a 15-foot (4.5 m) field stone obelisk in Rugby claiming to mark the center.