The Hemlock 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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74° on Nov. 11, 2020, the hottest reading for this week of the year since 1926. Next is 72° in 1973.
Hemlock’s center stands about 840 ft above sea level. Within three miles the land runs from 500 ft to 1,200 ft, a difference of 700 ft: hilly country. The highest named summit within 15 miles is Knob Mountain, about 1,790 ft, 10 miles east-northeast.
Under the town center the state geologic map shows Trimmers Rock Formation (siltstone, shale), from the Late Devonian, 359 to 384 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 14×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 7 mi of the line.
Siltstone, sandstone. Age: Late Devonian, 359 to 384 million years old. About 5 mi of the line.
Siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 5 mi of the line.
Siltstone. Age: Late Devonian, 359 to 384 million years old. About 3 mi of the line.
Sandstone. Age: Carboniferous, 324 to 359 million years old. About 2 mi of the line.
Shale. Age: Silurian, 422 to 445 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. 2 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 Hemlock reaches Chesapeake Bay and the Atlantic Ocean by way of West Hemlock Creek, Hemlock Creek, Fishing Creek and the Susquehanna: about 160 river miles.
Lake on the way: Lake Aldred.
110 miles of the trip are on the Susquehanna.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hemlock; river miles along the main stem, rounded.
Hemlock has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 19° in January. A normal year brings about 29 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Hemlock normally reaches 51° and falls to 32°. The record high is 70°, in 1964; the record low 18°, in 2019. The most rain on this date, 0.97 in, fell in 1972.
Normals 1991–2020 and records since 1926 at Sunbury, 17 miles southwest, 260 ft lower. NOAA, through RCC-ACIS.
