The Tennant plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
Tennant’s center stands about 4,820 ft above sea level. Within three miles the land runs from 4,670 ft to 6,230 ft, a difference of 1,560 ft: steep hill country. The highest named summit within 15 miles is The Whaleback, about 8,510 ft, 12 miles west-southwest.
Under the town center the state geologic map shows Quaternary volcanic flow rocks, unit 1 (Cascade Volcanic Field) (andesite, basalt), from the Late Pliocene to Pleistocene, less than 3.6 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Andesite, basalt. Age: Late Pliocene to Pleistocene, less than 3.6 million years old. About 14 mi of the line.
Andesite, basalt. Age: Late Pliocene to Pleistocene, less than 3.6 million years old. About 9 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.4 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.