The Duncombe 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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79° on Nov. 14, 1999, the hottest reading for this week of the year since 1893. Next is 77° in 2001.
Duncombe’s center stands about 1,110 ft above sea level. Within three miles the land runs from 1,090 ft to 1,120 ft, a difference of 30 ft: nearly flat ground.
Under the town center the state geologic map shows Augusta Group (dolostone, limestone), from the Early Mississippian to Middle Mississippian, 331 to 359 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 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, siltstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 17 mi of the line.
Dolostone, limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 4 mi of the line.
Dolostone, limestone. Age: Middle Mississippian to Late Mississippian, 324 to 347 million years old. About 3 mi of the line.
Shale, siltstone. Age: Middle Pennsylvanian, 307 to 315 million years old. About 0.5 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 Duncombe reaches the Gulf of America by way of Brushy Creek, the Des Moines and the Mississippi: about 1,630 river miles.
Lakes on the way: Roberts Creek and Big Creek Pounding Area.
1,330 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Duncombe; river miles along the main stem, rounded.
Duncombe has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 7° in January. A normal year brings about 33 inches of snow; with the rain, that comes to about 37 inches of water.
On November 14 Duncombe normally reaches 46° and falls to 25°. The record high is 79°, in 1999; the record low −9°, in 1959. The most rain on this date, 1.28 in, fell in 1926.
Normals 1991–2020 and records since 1893 at Webster City, 10 miles east. NOAA, through RCC-ACIS.
