The Modoc 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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78° on Nov. 11, 2020, the hottest reading for this week of the year since 1893. Next is 76° in 1931.
Modoc’s center stands about 1,170 ft above sea level. Within three miles the land runs from 1,090 ft to 1,220 ft, a difference of 130 ft: gently rolling country.
Under the town center the state geologic map shows Louisville Limestone through Brassfield Limestone, from the Silurian, 422 to 445 million years old.
The section below crosses 3 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.
Limestone. Age: Silurian, 422 to 445 million years old. About 21 mi of the line.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Shale, limestone. Age: Ordovician, 445 to 487 million years old. About 0.6 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 Modoc reaches the Gulf of America by way of the Whitewater, the Great Miami, the Ohio and the Mississippi: about 1,560 river miles.
970 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Modoc; river miles along the main stem, rounded.
Modoc has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 18° in January. A normal year brings about 21 inches of snow; with the rain, that comes to about 41 inches of water.
On November 14 Modoc normally reaches 52° and falls to 33°. The record high is 76°, in 1931; the record low 9°, in 1986. The most rain on this date, 3.01 in, fell in 1993.
Normals 1991–2020 and records since 1893 at Farmland 5 NNW, 14 miles north, 200 ft lower. NOAA, through RCC-ACIS.
