The Madison 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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Madison’s center stands about 500 ft above sea level. Within three miles the land runs from 420 ft to 910 ft, a difference of 490 ft: hilly country. The highest named summit within 15 miles is Mount Byrd, about 920 ft, 2 miles south.
Under the town center the state geologic map shows Dillsboro Formation (limestone, shale), from the Ordovician, 445 to 487 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 32×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Silurian, 422 to 445 million years old. About 9 mi of the line.
Dolostone. Age: Silurian, 422 to 445 million years old. About 4 mi of the line.
Limestone, 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.
Dolostone. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Madison reaches the Gulf of America by way of Crooked Creek, the Ohio and the Mississippi: about 1,390 river miles.
970 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Madison; river miles along the main stem, rounded.
