The Joyce 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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Joyce’s center stands about 140 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 Prairie Terraces (clay, silt, sand), from the Pleistocene, less than 2.6 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 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: Eocene, 34 to 56 million years old. About 8 mi of the line.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Clay, marl. Age: Eocene, 34 to 56 million years old. About 5 mi of the line.
Clay. Age: Holocene, less than 12,000 years old. About 5 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 Joyce reaches the Gulf of America by way of the Dugdemona, the Little River, the Black River, the Red River, the Atchafalaya and the Lower Atchafalaya: about 330 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 Joyce; river miles along the main stem, rounded.
