Geology of the Pacific Northwest along their course. The larger cataract was that of the upper Grand Coulee, where the river roared over an waterfall. The eroding power of the water plucked pieces of basalt from the precipice, causing the falls to retreat and self-destruct by cutting through to the Columbia River valley near what is now the Grand Coulee Dam. The other major cataract is now known as Dry Falls. It started near Soap Lake in Washington State, where less resistant basalt layers gave way before the great erosive power of this tremendous torrent and waterfalls developed. As in the upper Grand Coulee, the
Plum Coulee Plum Coulee Plum Coulee is an unincorporated urban community in the Municipality of Rhineland within the Canadian province of Manitoba that held town status prior to January 1, 2015. It is west of Altona, one hour southwest of Winnipeg and half an hour from the United States border. It is also the former home to the Plum Coulee Xpress hockey club. It has a man-made beach located in town. Philanthropist Saidye Bronfman was born in Plum Coulee. Plum Coulee's population of 800 is growing through land development. Working with local land owners, the former Town of Plum Coulee developed a