The Calvin 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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21° on Nov. 13, 2019, the coldest reading for this week of the year since 1893. Next is 22° in 1940.
Calvin’s center stands about 180 ft above sea level. Within three miles the land runs from 140 ft to 330 ft, a difference of 190 ft: gently rolling country.
Under the town center the state geologic map shows Alluvium (clay), from the Holocene, less than 12,000 years old.
The section below crosses 5 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.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 7 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 6 mi of the line.
Sand, clay. Age: Eocene, 34 to 56 million years old. About 5 mi of the line.
Clay, silt, sand. Age: Eocene, 34 to 56 million years old. About 4 mi of the line.
Clay, marl. Age: Eocene, 34 to 56 million years old. About 3 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 Calvin reaches the Gulf of America by way of Kyiaies Creek, the Dugdemona, the Little River, the Black River, the Red River, the Atchafalaya and the Lower Atchafalaya: about 350 river miles.
Lake on the way: Catahoula Lake.
100 miles of the trip are on the Atchafalaya.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Calvin; river miles along the main stem, rounded.
Calvin has a humid subtropical climate. Summer afternoons average 93° in July; winter nights fall to about 38° in January. About 55 inches of rain fall in a normal year.
On November 14 Calvin normally reaches 69° and falls to 45°. The record high is 86°, in 1955; the record low 25°, in 2019. The most rain on this date, 1.90 in, fell in 1998.
Normals 1991–2020 and records since 1893 from the Natchitoches Area threaded record (Natchitoches #2, 21 miles west-southwest). NOAA, through RCC-ACIS.
