The Sylvanite 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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69° on Nov. 12, 1999, the hottest reading for this week of the year since 1960. Next is 63° in 2021.
Sylvanite’s center stands about 2,730 ft above sea level. Within three miles the land runs from 2,650 ft to 5,400 ft, a difference of 2,750 ft: mountain country. The highest named summit within 15 miles is Rock Candy Mountain, about 7,170 ft, 13 miles north-northwest.
Under the town center the state geologic map shows Lower Prichard Formation (metasiltstone, argillite), from the Mesoproterozoic, 1 to 1.6 billion years old.
The section below crosses 9 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.
Metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 8 mi of the line.
Quartzite, metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 5 mi of the line.
Quartzite, argillite, metasiltstone. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 4 mi of the line.
Metasiltstone, argillite, quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 2 mi of the line.
Unconsolidated. Age: Pleistocene to Holocene, less than 1.8 million years old. About 2 mi of the line.
Metasiltstone, quartzite, argillite. Age: Mesoproterozoic, 1 to 1.6 billion 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. 3 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 Sylvanite reaches the Pacific Ocean by way of the Yaak, the Kootenai and the Columbia: about 820 river miles.
Lake on the way: Lake Umatilla.
460 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sylvanite; river miles along the main stem, rounded.
Sylvanite has a dry-summer warm-summer continental climate. Summer afternoons average 87° in July; winter nights fall to about 23° in January. About 24 inches of rain fall in a normal year.
On November 14 Sylvanite normally reaches 41° and falls to 30°. The record high is 63°, in 2021; the record low 6°, in 1978. The most rain on this date, 0.60 in, fell in 2021.
Normals 1991–2020 and records since 1960 at Troy, 16 miles south, 740 ft lower. NOAA, through RCC-ACIS.
