Plateaus can be formed by a number of processes, including upwelling ofvolcanic magma, extrusion of lava, and erosion by water and glaciers. read more
According to Wiki, (Piedmont (United States) - Wikipedia), : “The surface relief of the Piedmont is characterized by relatively low, rolling hills with heights above sea level between 200 feet (50 m) and 800 feet to 1,000 feet (250 m to 300 m). read more
Piedmont Plateau, looking east from Rocky Ridge in Maryland, c. 1898 The Piedmont is a plateau region located in the eastern United States. It sits between the Atlantic Coastal Plain and the main Appalachian Mountains, stretching from New Jersey in the north to central Alabama in the south. read more