The Derry 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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77° on Nov. 16, 1928, the hottest reading for this week of the year since 1895. Next is 72° in 1902.
Derry’s center stands about 550 ft above sea level. Within three miles the land runs from 520 ft to 1,070 ft, a difference of 550 ft: hilly country. The highest named summit within 15 miles is Knob Mountain, about 1,790 ft, 14 miles east.
Under the town center the state geologic map shows Hamilton Group (black-shale), from the Early Devonian to Middle Devonian, 384 to 422 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 19×. 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, shale. Age: Late Devonian, 359 to 384 million years old. About 12 mi of the line.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 7 mi of the line.
Shale, sandstone. Age: Silurian, 422 to 445 million years old. About 1 mi of the line.
Sandstone, siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 0.9 mi of the line.
Limestone. Age: Silurian to Devonian, 359 to 445 million years old. About 0.6 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million 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. 3 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 Derry reaches Chesapeake Bay and the Atlantic Ocean by way of Mud Creek, Chillisquaque Creek, the West Branch Susquehanna and the Susquehanna: about 150 river miles.
Lake on the way: Lake Aldred.
85 miles of the trip are on the Susquehanna.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Derry; river miles along the main stem, rounded.
Derry has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 20° in January. A normal year brings about 36 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Derry normally reaches 51° and falls to 34°. The record high is 69°, in 1989; the record low 13°, in 1986. The most rain on this date, 1.53 in, fell in 1972.
Normals 1991–2020 and records since 1895 from the Williamsport Area threaded record (Williamsport Regional Airport, 20 miles northwest). NOAA, through RCC-ACIS.
