The Cobden 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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Cobden’s center stands about 1,040 ft above sea level. Within three miles the land runs from 1,000 ft to 1,040 ft, a difference of 40 ft: nearly flat ground.
Under the town center the state geologic map shows Undifferentiated (conglomerate, sandstone, mudstone), from the Late Cretaceous, 72 to 100 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 60×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Conglomerate, sandstone, mudstone. Age: Late Cretaceous, 72 to 100 million years old. About 20 mi of the line.
Orthogneiss, migmatite. Age: Paleoarchean to Mesoarchean, 2.8 to 3.6 billion years old. About 2 mi of the line.
Granitic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 1 mi of the line.
Age: Paleoproterozoic, 1.8 to 2 billion 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.
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 Cobden reaches the Gulf of America by way of Sleepy Eye Creek, the Cottonwood, the Minnesota and the Mississippi: about 2,000 river miles.
Lake on the way: Lake Pepin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Cobden; river miles along the main stem, rounded.
