The Union 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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70° on Nov. 11, 2016, the hottest reading for this week of the year since 1965. Next is 69° in 1999.
Union’s center stands about 2,790 ft above sea level. Within three miles the land runs from 2,700 ft to 4,090 ft, a difference of 1,390 ft: steep hill country. The highest named summit within 15 miles is Cúuy’em Butte, about 7,850 ft, 15 miles east.
Under the town center the state geologic map shows Fanglomerate (mixed-clastic), from the Pleistocene to Holocene, less than 2.6 million 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 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.
Basalt. Age: Early Miocene to Middle Miocene, 12 to 23 million years old. About 15 mi of the line.
Basalt. Age: Middle Miocene to Late Miocene, 5.3 to 16 million years old. About 4 mi of the line.
Mixed-clastic. Age: Pleistocene to Holocene, less than 2.6 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 0.6 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 Union reaches the Pacific Ocean by way of Catherine Creek, the Grande Ronde, the Snake and the Columbia: about 640 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 Union; river miles along the main stem, rounded.
Union has a dry-summer warm-summer continental climate. Summer afternoons average 87° in August; winter nights fall to about 24° in December. A normal year brings about 9 inches of snow; with the rain, that comes to about 17 inches of water.
On November 14 Union normally reaches 48° and falls to 30°. The record high is 70°, in 2016; the record low 2°, in 1985. The most rain on this date, 0.63 in, fell in 1988.
Normals 1991–2020 and records since 1965 at La Grande, 13 miles northwest. NOAA, through RCC-ACIS.
