The Silverton 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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5° on Nov. 14, 2014, the coldest reading for this week of the year since 1975. Next is 7° in 2011.
Silverton’s center stands about 2,730 ft above sea level. Within three miles the land runs from 2,520 ft to 5,460 ft, a difference of 2,940 ft: mountain country. The highest named summit within 15 miles is Stevens Peak, about 6,810 ft, 10 miles east-southeast.
Under the town center the state geologic map shows Piegan Group (metasiltstone, quartzite), from the Mesoproterozoic, 1 to 1.6 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.
Quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 8 mi of the line.
Metasiltstone, quartzite, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 7 mi of the line.
Metasiltstone, quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 5 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 2 mi of the line.
Quartzite, argillite, metasiltstone. Age: Mesoproterozoic, 1 to 1.6 billion 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.
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 Silverton reaches the Pacific Ocean by way of the South Fork Coeur d'Alene, the Coeur d'Alene, the Spokane and the Columbia: about 820 river miles.
Lakes on the way: Harrison Slough and Lake Umatilla.
360 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Silverton; river miles along the main stem, rounded.
Silverton has a dry-summer warm-summer continental climate. Summer afternoons average 81° in July; winter nights fall to about 22° in February. About 37 inches of rain fall in a normal year.
On November 14 Silverton normally reaches 41° and falls to 28°. The record high is 57°, in 2021; the record low 5°, in 2014. The most rain on this date, 0.80 in, fell in 1990.
Normals 1991–2020 and records since 1975 at Mullan, 7 miles east-southeast, 470 ft higher. NOAA, through RCC-ACIS.
