The Yucaipa 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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Yucaipa’s center stands about 2,630 ft above sea level. Within three miles the land runs from 2,100 ft to 3,750 ft, a difference of 1,650 ft: steep hill country. The highest named summit within 15 miles is San Gorgonio Mountain, about 11,470 ft, 13 miles east-northeast.
Under the town center the state geologic map shows Older Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene, 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.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 5 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 5 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 5 mi of the line.
Gneiss. Age: Paleoproterozoic to Miocene, 5.3 to 2,500 million years old. About 4 mi of the line.
Tonalite. Age: Middle Jurassic to Late Cretaceous, 66 to 175 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 3 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 Yucaipa reaches the Pacific Ocean by way of Oak Glen Creek and the Santa Ana: about 75 river miles.
60 miles of the trip are on the Santa Ana.
Often dry. About 50% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Yucaipa; river miles along the main stem, rounded.
