The Yorklyn 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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76° on Nov. 15, 1973, the hottest reading for this week of the year since 1888. Next is 76° in 1993.
Yorklyn’s center stands about 430 ft above sea level. Within three miles the land runs from 350 ft to 980 ft, a difference of 630 ft: hilly country. The highest named summit within 15 miles is Chimney Rock, about 910 ft, 3 miles northeast.
The section below crosses 14 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 25×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Quartzite, schist. Age: Cambrian, 487 to 542 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.
Quartzite. Age: Cambrian, 487 to 542 million years old. About 3 mi of the line.
Schist, phyllite. Age: Paleozoic, 252 to 542 million years old. About 3 mi of the line.
Arkose. Age: Triassic, 202 to 252 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. 8 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 Yorklyn reaches Chesapeake Bay and the Atlantic Ocean by way of Kreutz Creek and the Susquehanna: about 55 river miles.
Lake on the way: Lake Aldred.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Yorklyn; river miles along the main stem, rounded.
Yorklyn has a hot-summer humid continental climate. Summer afternoons average 87° in July; winter nights fall to about 23° in January. A normal year brings about 30 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Yorklyn normally reaches 54° and falls to 36°. The record high is 74°, in 1989; the record low 19°, in 1986. The most rain on this date, 1.74 in, fell in 1995.
Normals 1991–2020 and records since 1888 from the Middletown-Harrisburg Area threaded record (Middletown Harrisburg Int'L Airport, 16 miles north-northwest, 130 ft lower). NOAA, through RCC-ACIS.
