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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16° on Nov. 16, 1996, the coldest reading for this week of the year since 1988. Next is 17° in 2017.
Union’s center stands about 590 ft above sea level. Within three miles the land runs from 530 ft to 790 ft, a difference of 260 ft: rolling country. The highest named summit within 15 miles is High Rock, about 1,210 ft, 9 miles northeast.
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 29×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Siltstone-mudstone, shale. Age: Triassic, 202 to 252 million years old. About 5 mi of the line.
Phyllite, mica-schist. Age: Paleozoic, 252 to 542 million years old. About 4 mi of the line.
Arkose. Age: Triassic, 202 to 252 million years old. About 3 mi of the line.
Mica-schist, quartzite. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Quartzite. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Basalt. Age: Jurassic, 145 to 202 million 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. 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 Union reaches Chesapeake Bay and the Atlantic Ocean by way of South Branch Conewago Creek, Conewago Creek and the Susquehanna: about 120 river miles.
Lake on the way: Lake Aldred.
50 miles of the trip are on Conewago Creek.
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 hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 24° in January. A normal year brings about 34 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Union normally reaches 54° and falls to 36°. The record high is 73°, in 1993; the record low 22°, in 2019. The most rain on this date, 1.59 in, fell in 1995.
Normals 1991–2020 and records since 1988 at Millers 4 NE, 13 miles east, 270 ft higher. NOAA, through RCC-ACIS.
