The Allison 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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78° on Nov. 13, 1999, the hottest reading for this week of the year since 1914. Next is 76° in 2012.
Allison’s center stands about 1,050 ft above sea level. Within three miles the land runs from 950 ft to 1,060 ft, a difference of 110 ft: gently rolling country.
Under the town center the state geologic map shows Cedar Valley Group (limestone, dolostone), from the Middle Devonian to Late Devonian, 374 to 388 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.
Limestone, dolostone. Age: Middle Devonian to Late Devonian, 374 to 388 million years old. About 21 mi of the line.
Shale, limestone, dolostone. Age: Late Devonian, 374 to 384 million years old. About 3 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 Allison reaches the Gulf of America by way of Freddeke Creek, the West Fork Cedar, the Cedar River, the Iowa and the Mississippi: about 1,640 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Allison; river miles along the main stem, rounded.
Allison has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 8° in January. About 35 inches of rain fall in a normal year.
On November 14 Allison normally reaches 45° and falls to 26°. The record high is 71°, in 1964; the record low −5°, in 1916. The most rain on this date, 0.82 in, fell in 1997.
Normals 1991–2020 and records since 1914 at Allison, here. NOAA, through RCC-ACIS.
