The Sedan 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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Sedan’s center stands about 5,550 ft above sea level. Within three miles the land runs from 5,360 ft to 6,170 ft, a difference of 810 ft: hilly country. The highest named summit within 15 miles is Sacagawea Peak, about 9,600 ft, 7 miles southwest.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Age: Pleistocene to Holocene, less than 1.8 million years old. About 8 mi of the line.
Claystone. Age: Late Cretaceous, 66 to 84 million years old. About 4 mi of the line.
Volcanic, conglomerate, sandstone. Age: Late Cretaceous, 72 to 84 million years old. About 4 mi of the line.
Conglomerate, quartzite, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 3 mi of the line.
Sandstone, limestone, shale. Age: Middle Jurassic to Early Cretaceous, 100 to 172 million years old. About 1 mi of the line.
Sandstone, conglomerate-sandstone. Age: Late Cretaceous, 66 to 72 million years old. About 0.8 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 6 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 Sedan reaches the Gulf of America by way of Flathead Creek, the Shields, the Yellowstone, the Missouri and the Mississippi: about 3,280 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Sharpe and Lake Francis Case.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sedan; river miles along the main stem, rounded.
