The Challenge-Brownsville 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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Challenge-Brownsville’s center stands about 2,560 ft above sea level. Within three miles the land runs from 1,730 ft to 3,120 ft, a difference of 1,390 ft: steep hill country. The highest named summit within 15 miles is Quartz Hill, about 4,380 ft, 12 miles north-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 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. 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 16 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 6 mi of the line.
Peridotite, serpentinite. Age: Neoproterozoic to Early Jurassic, 175 to 1,000 million years old. About 2 mi of the line.
Argillite, phyllite. Age: Permian to Jurassic, 145 to 299 million years old. About 0.6 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 million years old. About 0.5 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 Challenge-Brownsville reaches San Francisco Bay and the Pacific Ocean by way of Dry Creek, the Yuba, the Feather and the Sacramento: about 140 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 Challenge-Brownsville; river miles along the main stem, rounded.
