The Gilman 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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Gilman’s center stands about 650 ft above sea level. Within three miles the land runs from 630 ft to 660 ft, a difference of 30 ft: nearly flat ground.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale, sandstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 9 mi of the line.
Shale, sandstone, coal. Age: Middle Pennsylvanian to Late Pennsylvanian, 304 to 315 million years old. About 7 mi of the line.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 6 mi of the line.
Limestone. Age: Middle Devonian, 384 to 394 million years old. About 1 mi of the line.
Shale. Age: Middle Devonian to Late Devonian, 359 to 388 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.
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 Gilman reaches the Gulf of America by way of Prairie Creek, Spring Creek, the Iroquois, the Kankakee, the Illinois and the Mississippi: about 1,540 river miles.
Lake on the way: Peoria Lake.
1,190 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Gilman; river miles along the main stem, rounded.
