The Silas 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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Silas’s center stands about 230 ft above sea level. Within three miles the land runs from 120 ft to 340 ft, a difference of 220 ft: rolling country.
Under the town center the state geologic map shows Claiborne Group; Gosport Sand and Lisbon Formation undifferentiated in part, from the Eocene, 34 to 56 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 43×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand. Age: Eocene, 34 to 56 million years old. About 6 mi of the line.
Sand. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Claystone. Age: Eocene, 34 to 56 million years old. About 4 mi of the line.
Limestone. Age: Oligocene, 23 to 34 million years old. About 3 mi of the line.
Sand. Age: Miocene, 5.3 to 23 million years old. About 2 mi of the line.
Clay, limestone. Age: Eocene, 34 to 56 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 smaller units 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 Silas reaches Mobile Bay and the Gulf of America by way of Turkey Creek, the Tombigbee and the Mobile: about 140 river miles.
75 miles of the trip are on the Tombigbee.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Silas; river miles along the main stem, rounded.
