Columbia plateau is a region covering more than 200,000 square miles (518,000 sq. km) in Washington , Oregon,  Idaho and the Canadian province of British Colombia. Colombia river basin is a triangular area measuring 250 miles on each side. on its fingers the elevation  of the plateau is about 4,000 feet above sea level  and its lowest point is about 400 feet , plateau is formed about 16 million years ago  

Columbia plateau is a region covering 200,000 miles in washington , oregon and Idaho.The surface of the region is not a simple plateau.It includes plains and basins at low elevations; small plateaus , some level , some sloping ; hill lands , both gently and rolling and rough;and rugged mountain ranges rising above 10,000 feet . The climate is generally warm in summer and cold in winter . The slpoes of the mountain furnish lumber , principally from ponderosa and other pines.