The Placerville 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.
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Placerville’s center stands about 1,920 ft above sea level. Within three miles the land runs from 1,030 ft to 2,590 ft, a difference of 1,560 ft: steep hill country. The highest named summit within 15 miles is Saddle Mountain, about 5,170 ft, 14 miles northeast.
Under the town center the state geologic map shows Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (slate, graywacke), from the Triassic to Late Jurassic, 145 to 252 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. 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. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 7 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 5 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 million years old. About 4 mi of the line.
Slate, graywacke. Age: Triassic to Late Jurassic, 145 to 252 million years old. About 3 mi of the line.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 2 mi of the line.
Schist, gneiss. Age: Paleoproterozoic to Cretaceous, 66 to 2,500 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 smaller units along the line are not listed.
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.
A raindrop that lands in Placerville reaches San Francisco Bay and the Pacific Ocean by way of Hangtown Creek, Weber Creek and the Sacramento: about 110 river miles.
Lake on the way: Folsom Lake.
55 miles of the trip are on the Sacramento.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Placerville; river miles along the main stem, rounded.
