The Decatur 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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Decatur’s center stands about 1,860 ft above sea level. Within three miles the land runs from 1,480 ft to 2,000 ft, a difference of 520 ft: hilly country. The highest named summit within 15 miles is Lost Mountain, about 2,650 ft, 13 miles south-southwest.
Under the town center the state geologic map shows Allegheny Formation (sandstone), from the Carboniferous, 299 to 324 million years old.
The section below crosses 6 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.
Sandstone. Age: Carboniferous, 299 to 324 million years old. About 14 mi of the line.
Sandstone. Age: Carboniferous, 324 to 359 million years old. About 5 mi of the line.
Sandstone, siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Carboniferous, 299 to 324 million years old. About 2 mi of the line.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 million years old. About 0.9 mi of the line.
Sandstone, siltstone, mudstone. Age: Late Devonian, 359 to 384 million years old. About 0.7 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 Decatur reaches Chesapeake Bay and the Atlantic Ocean by way of Little Laurel Run, Laurel Run, Moshannon Creek, the West Branch Susquehanna and the Susquehanna: about 300 river miles.
Lake on the way: Lake Aldred.
140 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 Decatur; river miles along the main stem, rounded.
