Columbia River Basalt Group
- Diatomaceous earth (Wikipedia)
Diatomaceous earth (/ˌdaɪ.ətəˈmeɪʃəs/ DY-ə-tə-MAY-shəs), also known as diatomite (/daɪˈætəmaɪt/ dy-AT-ə-myte), celite, or kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 mm to less than 1 μm, but typically 10 to 200 μm. Depending on the granularity, this powder can have an abrasive feel, similar to pumice powder, and has a low density as a result of its high porosity. The typical chemical composition of oven-dried diatomaceous earth is 80–90% silica, with 2–4% alumina (attributed mostly to clay minerals), and 0.5–2% iron oxide.
- Steens Mountain (Wikipedia)
Steens Mountain is a large fault-block mountain in the northwest United States, located in Harney County, Oregon. Stretching some fifty miles (80 km) north to south, on its west side it rises from the Alvord Desert at an elevation of about 4,200 feet (1,280 m) to 9,738 feet (2,968 m) at the summit. Steens Mountain is not part of a mountain range but is properly a single mountain, the largest of Oregon’s fault-block mountains.
Columbia River Basalt Group map shows main regions of basalt exposure in Washington, Oregon, Idaho and Nevada, USA. (usgs.gov)