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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Seneca’s center stands about 4,660 ft above sea level. Within three miles the land runs from 4,660 ft to 5,290 ft, a difference of 630 ft: hilly country. The highest named summit within 15 miles is Canyon Mountain, about 7,910 ft, 15 miles north-northeast.
Under the town center the state geologic map shows Alluvial deposits (sand, gravel, silt), from the Holocene, less than 12,000 years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 9×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mudstone, shale. Age: Early Jurassic to Late Jurassic, 158 to 202 million years old. About 10 mi of the line.
Basalt, basaltic-andesite, andesite. Age: Late Oligocene to Pleistocene, 1.6 to 24 million years old. About 3 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 3 mi of the line.
Basalt, andesite. Age: Miocene, 5.3 to 23 million years old. About 3 mi of the line.
Rhyolite, dacite. Age: Early Miocene to Pliocene, 2.6 to 23 million years old. About 2 mi of the line.
Sandstone, siltstone, mudstone. Age: Miocene to Pliocene, 2.6 to 23 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. 1 smaller unit 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 Seneca reaches the desert basins of southern Oregon by way of the Silvies and the West Fork Silvies: about 110 river miles. The desert basins of southern Oregon has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
75 miles of the trip are on the Silvies.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Seneca; river miles along the main stem, rounded.
