The Spring Valley 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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82° on Nov. 12, 2014, the hottest reading for this week of the year since 1954. Next is 81° in 1995.
Spring Valley’s center stands about 1,310 ft above sea level. Within three miles the land runs from 1,120 ft to 2,840 ft, a difference of 1,720 ft: steep hill country. The highest named summit within 15 miles is Goat Mountain, about 6,100 ft, 15 miles north-northwest.
Under the town center the state geologic map shows Plio-Pleistocene and Pliocene loosely consolidated deposits (sandstone, conglomerate), from the Miocene to Pleistocene, less than 23 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 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.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 11 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 8 mi of the line.
Serpentinite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 3 mi of the line.
Melange. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 1 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 0.9 mi of the line.
Siltstone-mudstone. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 0.6 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 Spring Valley reaches San Francisco Bay and the Pacific Ocean by way of North Fork Cache Creek, Cache Creek, Prospect Slough, Cache Slough and the Sacramento: about 130 river miles.
110 miles of the trip are on Cache Creek.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Spring Valley; river miles along the main stem, rounded.
Spring Valley has a hot-summer Mediterranean climate. Summer afternoons average 91° in July; winter nights fall to about 32° in December. About 30 inches of rain fall in a normal year.
On November 14 Spring Valley normally reaches 64° and falls to 36°. The record high is 81°, in 1995; the record low 23°, in 1978. The most rain on this date, 3.07 in, fell in 1965.
Normals 1991–2020 and records since 1954 at Clearlake 4 SE, 11 miles south. NOAA, through RCC-ACIS.
