The Lytle Creek 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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Lytle Creek’s center stands about 3,450 ft above sea level. Within three miles the land runs from 2,490 ft to 5,870 ft, a difference of 3,380 ft: mountain country. The highest named summit within 15 miles is Mount San Antonio, about 10,040 ft, 9 miles west-northwest.
Under the town center the state geologic map shows Schist of various types and ages, unit 2 (Southern and West-central California) (mica-schist), from the Late Cretaceous to Eocene, 34 to 100 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 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.
Mica-schist. Age: Late Cretaceous to Eocene, 34 to 100 million years old. About 13 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 3 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 1 mi of the line.
Gneiss. Age: Paleoproterozoic to Miocene, 5.3 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.
A raindrop that lands in Lytle Creek reaches the Pacific Ocean by way of Middle Fork Lytle Creek, Lytle Creek and the Santa Ana: about 80 river miles.
60 miles of the trip are on the Santa Ana.
Often dry. About 40% 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 Lytle Creek; river miles along the main stem, rounded.
