The Griffin 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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3.70 inches of rain fell in two days, the most for this week of the year since records began in 1888. The next wettest, 3.52 inches, fell in 1957.
Griffin’s center stands about 380 ft above sea level. Within three miles the land runs from 360 ft to 540 ft, a difference of 180 ft: gently rolling country. The highest named summit within 15 miles is Boyd Hill, about 610 ft, 15 miles west.
Under the town center the state geologic map shows Mattoon Formation (shale, sandstone), 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.
Shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 13 mi of the line.
Shale. Age: Late Pennsylvanian, 304 to 307 million years old. About 7 mi of the line.
Shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 4 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 Griffin reaches the Gulf of America by way of the Black River, the Old Channel Wabash, the Ohio and the Mississippi: about 1,160 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 Griffin; river miles along the main stem, rounded.
Griffin has a humid subtropical climate. Summer afternoons average 88° in July; winter nights fall to about 23° in January. A normal year brings about 8 inches of snow; with the rain, that comes to about 47 inches of water.
On November 14 Griffin normally reaches 57° and falls to 36°. The record high is 83°, in 1955; the record low 12°, in 1986. The most rain on this date, 2.64 in, fell in 1957.
Normals 1991–2020 and records since 1888 at Mount Vernon, 19 miles south. NOAA, through RCC-ACIS.
