The San Antonio Heights 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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San Antonio Heights’s center stands about 2,160 ft above sea level. Within three miles the land runs from 1,430 ft to 4,780 ft, a difference of 3,350 ft: mountain country. The highest named summit within 15 miles is Mount San Antonio, about 10,040 ft, 9 miles north.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 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 2×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 12 mi of the line.
Schist, gneiss. Age: Paleoproterozoic to Cretaceous, 66 to 2,500 million years old. About 3 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 3 mi of the line.
Gneiss. Age: Paleoproterozoic to Miocene, 5.3 to 2,500 million years old. About 2 mi of the line.
Mica-schist. Age: Late Cretaceous to Eocene, 34 to 100 million years old. About 2 mi of the line.
Plutonic, gneiss. Age: Paleoproterozoic to Late Cretaceous, 66 to 2,500 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.
