The Kelly Ridge 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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Kelly Ridge’s center stands about 1,100 ft above sea level. Within three miles the land runs from 280 ft to 1,680 ft, a difference of 1,400 ft: steep hill country. The highest named summit within 15 miles is Swain Hill, about 4,100 ft, 13 miles east-northeast.
Under the town center the state geologic map shows Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains) (mafic-volcanic), from the Jurassic, 145 to 202 million years old.
The section below crosses 6 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.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 13 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 4 mi of the line.
Basalt. Age: Early Miocene to Middle Miocene, 14 to 16 million years old. About 2 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 million years old. About 1 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 1 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 0.7 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.
A raindrop that lands in Kelly Ridge reaches San Francisco Bay and the Pacific Ocean by way of the Feather and the Sacramento: about 150 river miles.
75 miles of the trip are on the Sacramento.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Kelly Ridge; river miles along the main stem, rounded.
