The Irwin 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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3.85 inches of rain fell in two days, the most for this week of the year since records began in 1890. The next wettest, 3.40 inches, fell in 1985.
Irwin’s center stands about 970 ft above sea level. Within three miles the land runs from 890 ft to 990 ft, a difference of 100 ft: gently rolling country.
Under the town center the state geologic map shows Cherokee Group - Cabaniss Subgroup, Krebs Subgroup (shale, sandstone, siltstone), from the Carboniferous, 299 to 324 million years old.
The section below crosses 2 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, siltstone, mudstone. Age: Carboniferous, 299 to 324 million years old. About 14 mi of the line.
Shale, sandstone, siltstone. Age: Carboniferous, 299 to 324 million years old. About 10 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 Irwin reaches the Gulf of America by way of Little Dry Wood Creek, the Marmaton, the Little Osage, the Osage, the Missouri and the Mississippi: about 1,630 river miles.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Irwin; river miles along the main stem, rounded.
Irwin has a hot-summer humid continental climate. Summer afternoons average 88° in July; winter nights fall to about 22° in January. A normal year brings about 7 inches of snow; with the rain, that comes to about 49 inches of water.
On November 14 Irwin normally reaches 57° and falls to 35°. The record high is 82°, in 1999; the record low 6°, in 1986. The most rain on this date, 2.25 in, fell in 1926.
Normals 1991–2020 and records since 1890 at Lamar 7 N, here. NOAA, through RCC-ACIS.
