The Harper 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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Harper’s center stands about 2,520 ft above sea level. Within three miles the land runs from 2,480 ft to 2,860 ft, a difference of 380 ft: rolling country. The highest named summit within 15 miles is South Mountain, about 5,240 ft, 12 miles west.
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 8×. 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, gravel, silt. Age: Holocene, less than 12,000 years old. About 7 mi of the line.
Sandstone, siltstone, mudstone. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 6 mi of the line.
Rhyolite, dacite. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 4 mi of the line.
Basalt. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 4 mi of the line.
Basalt, andesite. Age: Miocene, 5.3 to 23 million years old. About 2 mi of the line.
Rhyolite, diatomite, siltstone-mudstone. Age: Miocene, 5.3 to 23 million years old. About 1 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 Harper reaches the Pacific Ocean by way of Corbett Creek, the Malheur, the Snake and the Columbia: about 740 river miles.
Lakes on the way: Lake Umatilla, Brownlee Reservoir and Hells Canyon Reservoir.
240 miles of the trip are on the Snake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Harper; river miles along the main stem, rounded.
