The Brogan 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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Brogan’s center stands about 2,620 ft above sea level. Within three miles the land runs from 2,540 ft to 3,620 ft, a difference of 1,080 ft: steep hill country. The highest named summit within 15 miles is Juniper Mountain, about 6,410 ft, 12 miles west-southwest.
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 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, siltstone, mudstone. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 7 mi of the line.
Basalt, basaltic-andesite, andesite. Age: Late Oligocene to Pleistocene, 1.6 to 24 million years old. About 7 mi of the line.
Basalt. Age: Miocene, 5.3 to 23 million years old. About 4 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 2 mi of the line.
Rhyolite. Age: Miocene, 5.3 to 23 million years old. About 1 mi of the line.
Basalt. Age: Miocene to Pliocene, 2.6 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. 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 Brogan reaches the Pacific Ocean by way of Willow Creek, the Malheur, the Snake and the Columbia: about 730 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 Brogan; river miles along the main stem, rounded.
