The Island 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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Island’s center stands about 430 ft above sea level. Within three miles the land runs from 370 ft to 560 ft, a difference of 190 ft: gently rolling country. The highest named summit within 15 miles is Barrett Hill, about 660 ft, 8 miles northeast.
Under the town center the state geologic map shows Carbondale Formation (siltstone), from the Carboniferous, 299 to 324 million years old.
The section below crosses 3 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.
Sand, silt. Age: Pleistocene to Holocene, less than 2.6 million years old. About 18 mi of the line.
Siltstone. Age: Carboniferous, 299 to 324 million years old. About 3 mi of the line.
Siltstone. Age: Carboniferous, 299 to 324 million years old. About 3 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 Island reaches the Gulf of America by way of Cypress Creek, the Green River, the Ohio and the Mississippi: about 1,240 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 Island; river miles along the main stem, rounded.
