The Armagh 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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12° on Nov. 13, 1981, the coldest reading for this week of the year since 1938. Next is 16° in 1986.
Armagh’s center stands about 1,250 ft above sea level. Within three miles the land runs from 770 ft to 2,240 ft, a difference of 1,470 ft: steep hill country. The highest named summit within 15 miles is Thickhead Mountain, about 2,420 ft, 11 miles west.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 12×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, shale. Age: Ordovician, 445 to 487 million years old. About 7 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 7 mi of the line.
Sandstone. Age: Ordovician, 445 to 487 million years old. About 3 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 2 mi of the line.
Siltstone, shale. Age: Late Devonian, 359 to 384 million 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. 5 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 Armagh reaches Chesapeake Bay and the Atlantic Ocean by way of Treaster Run, Honey Creek, Kishacoquillas Creek, the Juniata and the Susquehanna: about 150 river miles.
Lake on the way: Lake Aldred.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Armagh; river miles along the main stem, rounded.
Armagh has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 21° in January. A normal year brings about 26 inches of snow; with the rain, that comes to about 42 inches of water.
On November 14 Armagh normally reaches 53° and falls to 33°. The record high is 75°, in 1989; the record low 17°, in 1986. The most rain on this date, 0.72 in, fell in 1972.
Normals 1991–2020 and records since 1938 at Lewistown, 13 miles south-southwest, 790 ft lower. NOAA, through RCC-ACIS.
