The Riverdale 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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−1° on Nov. 15, 1959, the coldest reading for this week of the year since 1871. Next is 3° in 1933.
Riverdale’s center stands about 600 ft above sea level. Within three miles the land runs from 550 ft to 710 ft, a difference of 160 ft: gently rolling country.
Under the town center the state geologic map shows Lower Cherokee Group and Raccoon Creek Group (shale, sandstone, siltstone), from the Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old.
The section below crosses 6 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.
Dolostone, mudstone. Age: Silurian, 425 to 434 million years old. About 9 mi of the line.
Shale, sandstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 8 mi of the line.
Shale, sandstone, siltstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 2 mi of the line.
Dolostone, limestone. Age: Middle Devonian, 384 to 394 million years old. About 2 mi of the line.
Limestone. Age: Middle Devonian, 384 to 394 million years old. About 1 mi of the line.
Shale. Age: Middle Devonian to Late Devonian, 359 to 388 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 Riverdale reaches the Gulf of America by way of the Mississippi: about 1,460 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Riverdale; river miles along the main stem, rounded.
Riverdale has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 15° in January. A normal year brings about 36 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Riverdale normally reaches 50° and falls to 31°. The record high is 75°, in 1971; the record low 0°, in 1959. The most rain on this date, 1.16 in, fell in 1968.
Normals 1991–2020 and records since 1871 from the Moline Area threaded record (Moline Quad City International Airport, 7 miles south-southwest). NOAA, through RCC-ACIS.
