The Grugan 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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75° on Nov. 11, 2020, the hottest reading for this week of the year since 1982. Next is 68° in 2012.
Grugan’s center stands about 1,790 ft above sea level. Within three miles the land runs from 590 ft to 2,170 ft, a difference of 1,580 ft: steep hill country. The highest named summit within 15 miles is Hyner Mountain, about 2,180 ft, 5 miles north-northeast.
Under the town center the state geologic map shows Burgoon Sandstone, from the Carboniferous, 324 to 359 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 11×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone. Age: Carboniferous, 324 to 359 million years old. About 11 mi of the line.
Sandstone, siltstone. Age: Devonian to Carboniferous, 324 to 422 million years old. About 10 mi of the line.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 million years old. About 2 mi of the line.
Sandstone, siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 0.9 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Grugan reaches Chesapeake Bay and the Atlantic Ocean by way of the West Branch Susquehanna and the Susquehanna: about 220 river miles.
Lake on the way: Lake Aldred.
90 miles of the trip are on the West Branch Susquehanna.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grugan; river miles along the main stem, rounded.
Grugan has a cold desert climate. Summer afternoons average 82° in July; winter nights fall to about 18° in January. Barely 0.0 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1982 at Alvin R Bush Dam, 17 miles west-northwest, 860 ft lower. NOAA, through RCC-ACIS.
