The Green 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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87° on Nov. 15, 2008, the hottest reading for this week of the year since 1950. Next is 82° in 2010.
Green Valley’s center stands about 120 ft above sea level. Within three miles the land runs from 20 ft to 1,460 ft, a difference of 1,440 ft: steep hill country. The highest named summit within 15 miles is Mount Vaca, about 2,800 ft, 11 miles north-northeast.
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 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 9 mi of the line.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 4 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 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. 2 smaller units along the line are not listed.
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 Green Valley reaches San Francisco Bay and the Pacific Ocean by way of Green Valley Creek and Suisun Slough: about 18 river miles.
Often dry. About 30% 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 Green Valley; river miles along the main stem, rounded.
Green Valley has a hot-summer Mediterranean climate. Summer afternoons average 90° in July; winter nights fall to about 40° in January. About 24 inches of rain fall in a normal year.
On November 14 Green Valley normally reaches 66° and falls to 46°. The record high is 79°, in 2008; the record low 22°, in 1985. The most rain on this date, 2.15 in, fell in 1972.
Normals 1991–2020 and records since 1950 at Fairfield, 5 miles east-northeast. NOAA, through RCC-ACIS.
