The Iron Mountain Lake 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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3° on Nov. 13, 2019, the coldest reading for this week of the year since 1893. Next is 8° in 1894.
Iron Mountain Lake’s center stands about 1,080 ft above sea level. Within three miles the land runs from 1,020 ft to 1,590 ft, a difference of 570 ft: hilly country. The highest named summit within 15 miles is Taum Sauk Mountain, about 1,800 ft, 10 miles southwest.
Under the town center the state geologic map shows Elvins Group - (including Derby-Doerun Dolomite, Davis Formation), Bonneterre Dolomite (dolostone, shale, siltstone), from the Cambrian, 487 to 497 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 21×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Alkali-feldspar-granite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 11 mi of the line.
Dolostone, shale, siltstone. Age: Cambrian, 487 to 497 million years old. About 7 mi of the line.
Rhyolite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 5 mi of the line.
Sandstone. Age: Cambrian, 487 to 497 million years old. About 2 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 Iron Mountain Lake reaches the Gulf of America by way of Indian Creek, the Saint Francis and the Mississippi: about 1,100 river miles.
690 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Iron Mountain Lake; river miles along the main stem, rounded.
Iron Mountain Lake has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 21° in January. A normal year brings about 12 inches of snow; with the rain, that comes to about 46 inches of water.
On November 14 Iron Mountain Lake normally reaches 55° and falls to 36°. The record high is 76°, in 1993; the record low 10°, in 2019. The most rain on this date, 4.20 in, fell in 1993.
Normals 1991–2020 and records since 1893 at Potosi 4 SW, 19 miles northwest. NOAA, through RCC-ACIS.
