The Clarence 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.
Clarence’s center stands about 120 ft above sea level. Within three miles the land runs from 90 ft to 180 ft, a difference of 90 ft: gently rolling country.
Under the town center the state geologic map shows Natural Levees (silt, clay), from the Holocene, less than 12,000 years old.
The section below crosses 6 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.
Silt, clay. Age: Holocene, less than 12,000 years old. About 8 mi of the line.
Sand, clay, lignite. Age: Paleocene, 56 to 66 million years old. About 7 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Clay, marl. Age: Eocene, 34 to 56 million years old. About 2 mi of the line.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 0.6 mi of the line.
Sand, clay. Age: Eocene, 34 to 56 million years old. About 0.4 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 Clarence reaches the Gulf of America by way of Chevreuille Bayou, the Red River, the Atchafalaya and the Lower Atchafalaya: about 300 river miles.
160 miles of the trip are on the Red River.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Clarence; river miles along the main stem, rounded.
Clarence 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 Clarence 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, 3 miles west). NOAA, through RCC-ACIS.
