The Herculaneum 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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Herculaneum’s center stands about 450 ft above sea level. Within three miles the land runs from 380 ft to 660 ft, a difference of 280 ft: rolling country. The highest named summit within 15 miles is Frisco Hill, about 860 ft, 9 miles north-northwest.
Under the town center the state geologic map shows Decorah Group, Plattin Group (limestone), from the Middle Ordovician, 459 to 471 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 37×. 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: Carboniferous, 324 to 359 million years old. About 7 mi of the line.
Limestone. Age: Middle Ordovician, 459 to 471 million years old. About 5 mi of the line.
Limestone, dolostone. Age: Late Ordovician, 447 to 454 million years old. About 5 mi of the line.
Dolostone, limestone. Age: Late Ordovician, 454 to 459 million years old. About 4 mi of the line.
Limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 2 mi of the line.
Sandstone, limestone, dolostone. Age: Middle Ordovician to Late Ordovician, 454 to 468 million years old. About 0.6 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 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 Herculaneum reaches the Gulf of America by way of Joachim Creek and the Mississippi: about 1,130 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Herculaneum; river miles along the main stem, rounded.
