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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9° on Nov. 16, 1933, the coldest reading for this week of the year since 1882. Next is 12° in 1883.
Gregg’s center stands about 1,240 ft above sea level. Within three miles the land runs from 1,060 ft to 1,960 ft, a difference of 900 ft: hilly country. The highest named summit within 15 miles is Thickhead Mountain, about 2,420 ft, 11 miles southwest.
Under the town center the state geologic map shows Coburn Formation through Nealmont Formation, undivided (limestone, shale), from the Ordovician, 445 to 487 million years old.
The section below crosses 12 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. Age: Ordovician, 445 to 487 million years old. About 7 mi of the line.
Sandstone, shale. Age: Ordovician, 445 to 487 million years old. About 4 mi of the line.
Limestone, shale. 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.
Sandstone. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Dolostone. Age: Cambrian, 487 to 542 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. 6 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 Penns Creek and the Susquehanna: about 180 river miles.
Lake on the way: Lake Aldred.
75 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 81° in July; winter nights fall to about 21° in January. A normal year brings about 44 inches of snow; with the rain, that comes to about 42 inches of water.
On November 14 Gregg normally reaches 49° and falls to 34°. The record high is 70°, in 1902; the record low 13°, in 1986. The most rain on this date, 0.66 in, fell in 1972.
Normals 1991–2020 and records since 1882 at State College, 16 miles west-southwest. NOAA, through RCC-ACIS.
