The Garrison 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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76° on Nov. 13, 1999, the hottest reading for this week of the year since 1893. Next is 75° in 1941.
Garrison’s center stands about 890 ft above sea level. Within three miles the land runs from 820 ft to 1,000 ft, a difference of 180 ft: gently rolling country.
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 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 13 mi of the line.
Shale, limestone, dolostone. Age: Late Devonian, 374 to 384 million years old. About 8 mi of the line.
Dolostone, limestone. Age: Middle Devonian, 384 to 394 million years old. About 3 mi of the line.
Limestone. Age: Silurian, 431 to 440 million years old. About 0.4 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 Garrison reaches the Gulf of America by way of Hinkle Creek, the Cedar River, the Iowa and the Mississippi: about 1,570 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Garrison; river miles along the main stem, rounded.
Garrison has a warm-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 8° in January. A normal year brings about 34 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Garrison normally reaches 45° and falls to 26°. The record high is 73°, in 1950; the record low 1°, in 1959. The most rain on this date, 1.25 in, fell in 1902.
Normals 1991–2020 and records since 1893 at Vinton, 7 miles east. NOAA, through RCC-ACIS.
