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
Birch Coulee Battlefield Birch Coulee Battlefield Birch Coulee Battlefield in Renville County, Minnesota, United States, was the site of the Battle of Birch Coulee, the costliest military engagement for U.S. forces during the Dakota War of 1862. It is now a historic site with self-guided trails and markers interpreting the battle from both sides. Birch Coulee was nominated to the National Register of Historic Places for having state-level significance in military history, and was listed in 1973. Birch Coulee Battlefield lies on what, in 1862, was open prairie stretching on to the north and west, with woods to the south. Defining the east