The Troy 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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73° on Nov. 12, 1999, the hottest reading for this week of the year since 1893. Next is 67° in 2016.
Troy’s center stands about 2,510 ft above sea level. Within three miles the land runs from 2,440 ft to 2,910 ft, a difference of 470 ft: hilly country. The highest named summit within 15 miles is Moscow Mountain, about 4,970 ft, 6 miles northwest.
Under the town center the state geologic map shows Volcanic rocks (basalt, andesite), from the Early Oligocene to Late Oligocene, 26 to 32 million years old.
The section below crosses 4 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.
Basalt, basaltic-andesite. Age: Early Miocene to Late Miocene, 6 to 18 million years old. About 12 mi of the line.
Granodiorite, granite. Age: Early Cretaceous to Late Cretaceous, 67 to 107 million years old. About 10 mi of the line.
Basalt, andesite. Age: Early Oligocene to Late Oligocene, 26 to 32 million years old. About 2 mi of the line.
Quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 0.2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Troy reaches the Pacific Ocean by way of West Fork Little Bear Creek, Little Bear Creek, the Potlatch, the Clearwater, the Snake and the Columbia: about 500 river miles.
Lake on the way: Lake Umatilla.
210 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Troy; river miles along the main stem, rounded.
Troy has a dry-summer warm-summer continental climate. Summer afternoons average 86° in August; winter nights fall to about 22° in January. A normal year brings about 51 inches of snow; with the rain, that comes to about 28 inches of water.
On November 14 Troy normally reaches 45° and falls to 28°. The record high is 65°, in 1999; the record low −4°, in 1955. The most rain on this date, 0.72 in, fell in 1941.
Normals 1991–2020 and records since 1893 at Moscow U Of I, 9 miles west, 120 ft higher. NOAA, through RCC-ACIS.
