The Shirleysburg 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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Shirleysburg’s center stands about 580 ft above sea level. Within three miles the land runs from 560 ft to 1,840 ft, a difference of 1,280 ft: steep hill country. The highest named summit within 15 miles is Butler Knob, about 2,340 ft, 5 miles west.
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 18 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.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 5 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 million years old. About 3 mi of the line.
Limestone. Age: Silurian to Devonian, 359 to 445 million years old. About 2 mi of the line.
Sandstone. Age: Carboniferous, 324 to 359 million years old. About 2 mi of the line.
Siltstone, shale. Age: Late Devonian, 359 to 384 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. 12 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 Shirleysburg reaches Chesapeake Bay and the Atlantic Ocean by way of Aughwick Creek, the Juniata and the Susquehanna: about 170 river miles.
Lake on the way: Lake Aldred.
80 miles of the trip are on the Juniata.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Shirleysburg; river miles along the main stem, rounded.
