The Monument 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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Monument’s center stands about 2,020 ft above sea level. Within three miles the land runs from 1,970 ft to 3,790 ft, a difference of 1,820 ft: steep hill country. The highest named summit within 15 miles is Hamilton Mountain, about 5,330 ft, 10 miles south-southeast.
Under the town center the state geologic map shows John Day Formation of east-central Oregon (sandstone-mudstone), from the Late Eocene to Early Miocene, 16 to 38 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt. Age: Early Miocene to Middle Miocene, 12 to 23 million years old. About 19 mi of the line.
Sandstone-mudstone. Age: Late Eocene to Early Miocene, 16 to 38 million years old. About 3 mi of the line.
Andesite. Age: Paleocene to Early Oligocene, 28 to 66 million years old. About 0.7 mi of the line.
Quartz-diorite, granitic, granodiorite. Age: Late Triassic to Late Cretaceous, 66 to 208 million years old. About 0.6 mi of the line.
Metaandesite, metabasalt, spilite. Age: Permian to Triassic, 202 to 299 million years old. About 0.3 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 Monument reaches the Pacific Ocean by way of the North Fork John Day, the John Day and the Columbia: about 410 river miles.
Lake on the way: Lake Umatilla.
210 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Monument; river miles along the main stem, rounded.
