The Bluffs 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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4.38 inches of rain fell in two days, the most for this week of the year since records began in 1992. The next wettest, 3.15 inches, fell in 2015.
Bluffs’s center stands about 480 ft above sea level. Within three miles the land runs from 430 ft to 630 ft, a difference of 200 ft: gently rolling country. The highest named summit within 15 miles is Calvert Hill, about 740 ft, 13 miles southwest.
Under the town center the state geologic map shows Warsaw Formation and Salem Limestone, from the Middle Mississippian, 331 to 347 million years old.
The section below crosses 4 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, coal. Age: Middle Pennsylvanian to Late Pennsylvanian, 304 to 315 million years old. About 11 mi of the line.
Limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 9 mi of the line.
Shale, sandstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 3 mi of the line.
Limestone. Age: Middle Mississippian, 331 to 347 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 Bluffs reaches the Gulf of America by way of Wolf Run, Coon Run, the Illinois and the Mississippi: about 1,260 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Bluffs; river miles along the main stem, rounded.
Bluffs has a hot-summer humid continental climate. Summer afternoons average 87° in July; winter nights fall to about 18° in January. A normal year brings about 21 inches of snow; with the rain, that comes to about 39 inches of water.
Normals 1991–2020 and records since 1992 at Perry 6 NW, 16 miles west-northwest, 170 ft higher. NOAA, through RCC-ACIS.
