The Gregg 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.
Gregg’s center stands about 490 ft above sea level. Within three miles the land runs from 450 ft to 1,740 ft, a difference of 1,290 ft: steep hill country. The highest named summit within 15 miles is Jones Mountain, about 2,180 ft, 14 miles southwest.
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 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.
Shale, sandstone. Age: Silurian, 422 to 445 million years old. About 5 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 5 mi of the line.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 4 mi of the line.
Sandstone, shale. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Shale. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Shale. Age: Silurian, 422 to 445 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. 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 Gregg reaches Chesapeake Bay and the Atlantic Ocean by way of White Deer Hole 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 Gregg; river miles along the main stem, rounded.
Gregg 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 Gregg 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, 9 miles north). NOAA, through RCC-ACIS.
