Rock Island Dam Island Pool. Rock Island Dam is constructed on Columbia River basalt similar to that which is exposed on the cliffs near the dam. These columnar basalts were formed from lava flows during the mid- to late-Miocene Epoch, some 14 to 16 million years ago. The rock is strong and durable and provides a very stable foundation for the structure. Columbia River stream flows at the Project averaged 73,700 cubic feet per second (2090 m³/s), a decrease of 37% from 2000 and 63% of the 20 year average of 116,700 cubic feet per second (3305 m³/s). The Rock Island Hydro Project
Little Lava Lake Little Lava Lake Little Lava Lake lies in the Cascade Range about west-southwest of Bend in the U.S. state of Oregon. A close neighbor of Lava Lake, from which it is separated by solidified lava, Little Lava Lake is at an elevation of in the Deschutes National Forest. Generally considered the source of the Deschutes River, the lake covers to an average depth of . Lava Lake, Little Lava Lake, and other nearby lakes formed after lava flows from Mount Bachelor altered drainage patterns in the area. Solidified lava flows are visible along the shorelines of both lakes, and the