The Tonto Basin 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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27° on Nov. 15, 2022, the coldest reading for this week of the year since 1905. Next is 28° in 1938.
Tonto Basin’s center stands about 2,250 ft above sea level. Within three miles the land runs from 2,190 ft to 3,920 ft, a difference of 1,730 ft: steep hill country. The highest named summit within 15 miles is Four Peaks, about 7,540 ft, 10 miles south.
Under the town center the state geologic map shows Holocene surficial deposits (silt, clay), from the Holocene, less than 10,000 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 4×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Conglomerate, sandstone. Age: Early Miocene to Pleistocene, 2 to 16 million years old. About 10 mi of the line.
Silt, clay. Age: Holocene, less than 10,000 years old. About 5 mi of the line.
Metasedimentary, metavolcanic, gneiss. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 3 mi of the line.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 3 mi of the line.
Gravel, sand. Age: Pleistocene, less than 0.8 million years old. About 2 mi of the line.
Gravel, sand. Age: Late Pliocene to Pleistocene, 0.8 to 3 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 Tonto Basin reaches the Gulf of California by way of Tonto Creek, the Salt River, the Gila and the Colorado: about 430 river miles.
200 miles of the trip are on the Gila.
Often dry. About 60% 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 Tonto Basin; river miles along the main stem, rounded.
Tonto Basin has a hot semi-arid climate. Summer afternoons average 104° in July; winter nights fall to about 40° in January. About 16 inches of rain fall in a normal year.
On November 14 Tonto Basin normally reaches 72° and falls to 48°. The record high is 85°, in 1953; the record low 28°, in 1938. The most rain on this date, 1.63 in, fell in 1968.
Normals 1991–2020 and records since 1905 at Roosevelt 1 S, 17 miles southeast, 360 ft higher. NOAA, through RCC-ACIS.
