The Williamson 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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79° on Nov. 15, 2016, the hottest reading for this week of the year since 1948. Next is 77° in 1967.
Williamson’s center stands about 5,050 ft above sea level. Within three miles the land runs from 4,880 ft to 5,930 ft, a difference of 1,050 ft: steep hill country. The highest named summit within 15 miles is Granite Mountain, about 7,250 ft, 4 miles south-southwest.
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 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 12 mi of the line.
Conglomerate, sandstone. Age: Early Miocene to Pleistocene, 2 to 16 million years old. About 7 mi of the line.
Gravel, sand. Age: Late Pliocene to Pleistocene, 0.8 to 3 million years old. About 3 mi of the line.
Basalt, andesite, dacite. Age: Middle Eocene to Late Miocene, 11 to 38 million years old. About 2 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 Williamson reaches the Gulf of California by way of the Verde, the Salt River, the Gila and the Colorado: about 570 river miles.
200 miles of the trip are on the Gila.
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.
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 Williamson; river miles along the main stem, rounded.
Williamson has a cold semi-arid climate. Summer afternoons average 90° in July; winter nights fall to about 25° in December. About 13 inches of rain fall in a normal year.
On November 14 Williamson normally reaches 63° and falls to 33°. The record high is 75°, in 1999; the record low 18°, in 1985. The most rain on this date, 0.97 in, fell in 1993.
Normals 1991–2020 and records since 1948 at Prescott Love Field, 7 miles east-southeast. NOAA, through RCC-ACIS.
