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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80° on Nov. 11, 2020, the hottest reading for this week of the year since 1943. Next is 72° in 2021.
Irwin’s center stands about 1,040 ft above sea level. Within three miles the land runs from 870 ft to 1,250 ft, a difference of 380 ft: rolling country. The highest named summit within 15 miles is Sheppler Hill, about 1,430 ft, 13 miles south-southwest.
Under the town center the state geologic map shows Monongahela Group (limestone, shale, sandstone), from the Carboniferous, 299 to 324 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 26×. 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, shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 12 mi of the line.
Shale, clastic. Age: Carboniferous, 299 to 324 million years old. About 7 mi of the line.
Shale. Age: Carboniferous, 299 to 324 million years old. About 4 mi of the line.
Sandstone, shale. Age: Carboniferous to Permian, 252 to 324 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 Irwin reaches the Gulf of America by way of Tinkers Run, Brush Creek, Turtle Creek, the Monongahela, the Ohio and the Mississippi: about 1,970 river miles.
970 miles of the trip are on the Ohio.
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 84° in July; winter nights fall to about 22° in January. About 41 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1943 at Braddock Lock 2, 10 miles west-northwest, 310 ft lower. NOAA, through RCC-ACIS.
