The Chain of Rocks 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.
Sunny
Partly cloudy; warmer
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4.19 inches of rain fell in two days, the most for this week of the year since records began in 1957. The next wettest, 2.96 inches, fell in 2003.
Chain of Rocks’s center stands about 490 ft above sea level. Within three miles the land runs from 440 ft to 570 ft, a difference of 130 ft: gently rolling country. The highest named summit within 15 miles is McAdams Peak, about 830 ft, 15 miles east-northeast.
Under the town center the state geologic map shows Meramecian Series (limestone), from the Carboniferous, 324 to 359 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 60×. 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. Age: Carboniferous, 324 to 359 million years old. About 9 mi of the line.
Limestone. Age: Carboniferous, 324 to 359 million years old. About 7 mi of the line.
Clay, silt, sand. Age: Holocene, less than 12,000 years old. About 5 mi of the line.
Sandstone, limestone, dolostone. Age: Middle Ordovician to Late Ordovician, 454 to 468 million years old. About 1 mi of the line.
Limestone, dolostone. Age: Late Ordovician, 447 to 454 million years old. About 0.9 mi of the line.
Shale, limestone. Age: Late Ordovician, 445 to 454 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. 3 smaller units along the line are not listed.
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 Chain of Rocks reaches the Gulf of America by way of the Cuivre and the Mississippi: about 1,220 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Chain of Rocks; river miles along the main stem, rounded.
Chain of Rocks has a hot-summer humid continental climate. Summer afternoons average 88° in July; winter nights fall to about 21° in January. A normal year brings about 14 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Chain of Rocks normally reaches 56° and falls to 35°. The record high is 80°, in 1989; the record low 10°, in 1986. The most rain on this date, 2.00 in, fell in 1993.
Normals 1991–2020 and records since 1957 at Weldon Spring Nws, 16 miles south-southeast, 120 ft higher. NOAA, through RCC-ACIS.
