The Alta 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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68° on Nov. 15, 1999, the hottest reading for this week of the year since 1909. Next is 67° in 1934.
Alta’s center stands about 6,440 ft above sea level. Within three miles the land runs from 6,200 ft to 8,180 ft, a difference of 1,980 ft: steep hill country. The highest named summit within 15 miles is Grand Teton, about 13,280 ft, 12 miles east.
Under the town center the state geologic map shows Alluvium and Colluvium (clay, silt, sand), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 10 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.
Coarse-detrital, fine-detrital. Age: Pleistocene, less than 2.6 million years old. About 7 mi of the line.
Limestone, dolostone. Age: Late Devonian to Carboniferous, 324 to 384 million years old. About 5 mi of the line.
Gravel. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Granite. Age: Archean. About 2 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 2 mi of the line.
Dolostone, limestone. Age: Middle Cambrian to Late Ordovician, 445 to 521 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. 4 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 Alta reaches the Pacific Ocean by way of the Teton, the Henrys Fork, the Snake and the Columbia: about 1,240 river miles.
Lakes on the way: American Falls Reservoir, Lake Umatilla, Brownlee Reservoir and Cove Arm Lake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alta; river miles along the main stem, rounded.
Alta has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 12° in January. A normal year brings about 113 inches of snow; with the rain, that comes to about 25 inches of water.
On November 14 Alta normally reaches 39° and falls to 20°. The record high is 66°, in 1999; the record low −13°, in 1916. The most rain on this date, 0.90 in, fell in 1988.
Normals 1991–2020 and records since 1909 at Alta 1 NNW, here. NOAA, through RCC-ACIS.
