The Seneca 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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4.14 inches of rain fell in two days, the most for this week of the year since records began in 1896. The next wettest, 3.95 inches, fell in 1935.
Seneca’s center stands about 950 ft above sea level. Within three miles the land runs from 780 ft to 980 ft, a difference of 200 ft: rolling country. The highest named summit within 15 miles is Oconee Mountain, about 1,890 ft, 15 miles north-northwest.
Under the town center the state geologic map shows Wallhalla metamorphic suite (hornblende-gneiss, amphibolite), from the Neoproterozoic to Cambrian, 487 to 1,000 million 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 34×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Hornblende-gneiss, amphibolite. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 10 mi of the line.
Biotite-gneiss, mica-schist. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 7 mi of the line.
Gneiss. Age: Ordovician, 445 to 487 million years old. About 3 mi of the line.
Metasedimentary. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 2 mi of the line.
Gneiss. Age: Silurian to Devonian, 359 to 445 million years old. About 1 mi of the line.
Gneiss. Age: Ordovician to Silurian, 422 to 487 million years old. About 0.9 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 Seneca reaches the Atlantic Ocean by way of Coneross Creek, the Seneca, Little Beaverdam Creek and the Savannah: about 320 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Seneca; river miles along the main stem, rounded.
Seneca has a humid subtropical climate. Summer afternoons average 91° in July; winter nights fall to about 32° in January. About 52 inches of rain fall in a normal year, with about 2 inches of snow.
On November 14 Seneca normally reaches 65° and falls to 40°. The record high is 82°, in 1931; the record low 23°, in 2013. The most rain on this date, 0.91 in, fell in 1908.
Normals 1991–2020 and records since 1896 at Clemson University, 8 miles east-southeast, 150 ft lower. NOAA, through RCC-ACIS.
