The Grand Tower 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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Mostly sunny; warmer
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4.93 inches of rain fell in two days, the most for this week of the year since records began in 1898. The next wettest, 4.54 inches, fell in 1993.
Grand Tower’s center stands about 360 ft above sea level. Within three miles the land runs from 320 ft to 640 ft, a difference of 320 ft: rolling country. The highest named summit within 15 miles is Bald Knob, about 1,020 ft, 10 miles east-southeast.
Under the town center the state geologic map shows Tamms Group (limestone), from the Silurian to Early Devonian, 394 to 425 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: Middle Ordovician, 459 to 471 million years old. About 9 mi of the line.
Limestone. Age: Silurian to Early Devonian, 394 to 425 million years old. About 7 mi of the line.
Limestone, sandstone, shale. Age: Late Mississippian, 324 to 331 million years old. About 3 mi of the line.
Shale, sandstone. Age: Early Pennsylvanian, 315 to 324 million years old. About 2 mi of the line.
Limestone, sandstone. Age: Early Devonian to Late Devonian, 359 to 422 million years old. About 0.8 mi of the line.
Limestone. Age: Silurian, 422 to 445 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. 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 Grand Tower reaches the Gulf of America by way of the Mississippi: about 1,050 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grand Tower; river miles along the main stem, rounded.
Grand Tower has a humid subtropical climate. Summer afternoons average 88° in July; winter nights fall to about 25° in January. About 44 inches of rain fall in a normal year.
On November 14 Grand Tower normally reaches 57° and falls to 35°. The record high is 78°, in 1978; the record low 10°, in 1986. The most rain on this date, 1.60 in, fell in 1993.
Normals 1991–2020 and records since 1898 from the Carbondale Area threaded record (Carbondale Southern Illinois Airport, 18 miles northeast). NOAA, through RCC-ACIS.
