The Round 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. 14, 1999, the hottest reading for this week of the year since 1940. Next is 79° in 1995.
Round Valley’s center stands about 4,890 ft above sea level. Within three miles the land runs from 4,040 ft to 5,570 ft, a difference of 1,530 ft: steep hill country. The highest named summit within 15 miles is Mazatzal Peak, about 7,840 ft, 13 miles southwest.
Under the town center the state geologic map shows Early Proterozoic granitic rocks (granite, granodiorite, tonalite), from the Paleoproterozoic, 1.6 to 1.8 billion 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 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.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 12 mi of the line.
Metavolcanic. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 6 mi of the line.
Conglomerate, sandstone. Age: Early Miocene to Pleistocene, 2 to 16 million years old. About 4 mi of the line.
Quartzite. Age: Paleoproterozoic, 1.6 to 1.7 billion years old. About 2 mi of the line.
Metasedimentary, metavolcanic, gneiss. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 0.9 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 Round Valley reaches the Gulf of California by way of Gibson Creek, Tonto Creek, the Salt River, the Gila and the Colorado: about 470 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 Round Valley; river miles along the main stem, rounded.
Round Valley has a hot-summer Mediterranean climate. Summer afternoons average 93° in July; winter nights fall to about 26° in January. A normal year brings about 18 inches of snow; with the rain, that comes to about 20 inches of water.
On November 14 Round Valley normally reaches 65° and falls to 31°. The record high is 82°, in 1999; the record low 20°, in 1971. The most rain on this date, 0.85 in, fell in 1993.
Normals 1991–2020 and records since 1940 at Payson, 4 miles northwest. NOAA, through RCC-ACIS.
