The Groveland 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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Groveland’s center stands about 2,900 ft above sea level. Within three miles the land runs from 2,040 ft to 3,560 ft, a difference of 1,520 ft: steep hill country. The highest named summit within 15 miles is Duckwall Mountain, about 5,800 ft, 11 miles northeast.
Under the town center the state geologic map shows Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada) (argillite, quartzite, phyllite), from the Ordovician to Triassic, 202 to 487 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.
Argillite, quartzite, phyllite. Age: Ordovician to Triassic, 202 to 487 million years old. About 14 mi of the line.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 6 mi of the line.
Slate, graywacke. Age: Triassic to Late Jurassic, 145 to 252 million years old. About 2 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 1 mi of the line.
Mafic-volcanic, greenstone. Age: Paleozoic to Mesozoic, 66 to 542 million years old. About 1 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 Groveland reaches San Francisco Bay and the Pacific Ocean by way of Big Creek, the Tuolumne, the San Joaquin and New York Slough: about 170 river miles.
Lake on the way: Don Pedro Reservoir.
80 miles of the trip are on the San Joaquin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Groveland; river miles along the main stem, rounded.
