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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87° on Nov. 12, 1999, the hottest reading for this week of the year since 1925. Next is 85° in 1967.
Spring Valley’s center stands about 3,940 ft above sea level. Within three miles the land runs from 3,700 ft to 4,360 ft, a difference of 660 ft: hilly country. The highest named summit within 15 miles is Mount Union, about 7,940 ft, 15 miles west-northwest.
Under the town center the state geologic map shows Pliocene to middle Miocene deposits (conglomerate, sandstone), from the Early Miocene to Pleistocene, 2 to 16 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 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt. Age: Early Miocene to Late Miocene, 8 to 16 million years old. About 14 mi of the line.
Metavolcanic. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 4 mi of the line.
Conglomerate, sandstone. Age: Early Miocene to Pleistocene, 2 to 16 million years old. About 3 mi of the line.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 2 mi of the line.
Metasedimentary, schist. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 0.7 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 the Gulf of California by way of Big Bug Creek, the Agua Fria, the Gila and the Colorado: about 420 river miles.
200 miles of the trip are on the Gila.
Often dry. About 70% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
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 cold semi-arid climate. Summer afternoons average 96° in July; winter nights fall to about 33° in December. About 15 inches of rain fall in a normal year, with about 1 inch of snow.
On November 14 Spring Valley normally reaches 68° and falls to 40°. The record high is 84°, in 2021; the record low 26°, in 2000. The most rain on this date, 1.05 in, fell in 1993.
Normals 1991–2020 and records since 1925 at Cordes, 3 miles south, 170 ft lower. NOAA, through RCC-ACIS.
