The Alto Pass 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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6.62 inches of rain fell in two days, the most for this week of the year since records began in 1887. The next wettest, 3.32 inches, fell in 1957.
Alto Pass’s center stands about 740 ft above sea level. Within three miles the land runs from 410 ft to 910 ft, a difference of 500 ft: hilly country. The highest named summit within 15 miles is Bald Knob, about 1,020 ft, 2 miles southwest.
Under the town center the state geologic map shows Caseyville Formation (shale, sandstone), from the Early Pennsylvanian, 315 to 324 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 28×. 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. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 8 mi of the line.
Limestone. Age: Silurian to Early Devonian, 394 to 425 million years old. About 7 mi of the line.
Shale, sandstone. Age: Early Pennsylvanian, 315 to 324 million years old. About 4 mi of the line.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Limestone, sandstone, shale. Age: Late Mississippian, 324 to 331 million years old. About 2 mi of the line.
Limestone, sandstone. Age: Early Devonian to Late Devonian, 359 to 422 million years old. About 0.9 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Alto Pass reaches the Gulf of America by way of Cedar Creek, the Big Muddy and the Mississippi: about 1,090 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alto Pass; river miles along the main stem, rounded.
Alto Pass has a humid subtropical climate. Summer afternoons average 90° in July; winter nights fall to about 25° in January. A normal year brings about 10 inches of snow; with the rain, that comes to about 51 inches of water.
On November 14 Alto Pass normally reaches 60° and falls to 37°. The record high is 79°, in 1999; the record low 10°, in 1986. The most rain on this date, 2.04 in, fell in 1993.
Normals 1991–2020 and records since 1887 at Anna 4 N, 5 miles southeast, 150 ft lower. NOAA, through RCC-ACIS.
