Columbia River Basalt Group
- Tetrahedron (Wikipedia)
In geometry, a tetrahedron (pl.: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertices. The tetrahedron is the simplest of all the ordinary convex polyhedra.
- Klickitat River (Wikipedia)
The Klickitat River is a tributary of the Columbia River, nearly 96 miles (154 km) long, in south-central Washington in the United States. It drains a rugged plateau area on the eastern side of the Cascade Range northeast of Portland, Oregon. In 1986, 10 miles (16 km) of the river were designated Wild and Scenic from the confluence with Wheeler Creek, near the town of Pitt, to the confluence with the Columbia River.
Columbia River Basalt Group map shows main regions of basalt exposure in Washington, Oregon, Idaho and Nevada, USA. (usgs.gov)