The El Portal 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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El Portal’s center stands about 1,920 ft above sea level. Within three miles the land runs from 1,740 ft to 5,500 ft, a difference of 3,760 ft: mountain country. The highest named summit within 15 miles is Mount Starr King, about 9,000 ft, 15 miles east.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 3×. 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 11 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 11 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Mafic-volcanic. Age: Jurassic, 145 to 202 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 El Portal reaches San Francisco Bay and the Pacific Ocean by way of the Merced, the San Joaquin and New York Slough: about 230 river miles.
Lake on the way: Lake McClure.
120 miles of the trip are on the San Joaquin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of El Portal; river miles along the main stem, rounded.
