 It is characterized by a number of dikes called the Chief Joseph Dike Swarm near Joseph, Enterprise, Troy and Walla Walla through which the lava upwelling occurred (estimates range to up to 20,000 such dikes).Many of the dikes were fissures wide and up to in length, allowing for huge quantities of magma upwelling.Much of the lava flowed north into Washington as well as down the Columbia River channel to the Pacific Ocean; the tremendous flows created the Columbia River Plateau.