The Johnson 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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Johnson’s center stands about 1,430 ft above sea level. Within three miles the land runs from 1,380 ft to 1,490 ft, a difference of 110 ft: gently rolling country.
Under the town center the state geologic map shows Felsic metavolcanic rocks of 1835- to 1845-Ma age group (rhyolite, dacite), from the Paleoproterozoic, 1.8 to 1.8 billion years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 58×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Gneiss, amphibolite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 9 mi of the line.
Basalt, basaltic-andesite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 4 mi of the line.
Granodiorite, tonalite. Age: Paleoproterozoic, 1.8 to 1.8 billion years old. About 3 mi of the line.
Alkali-feldspar-granite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Metavolcanic. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Rhyolite, dacite. Age: Paleoproterozoic, 1.8 to 1.8 billion years old. About 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 Johnson reaches the Gulf of America by way of Randall Creek, the Big Eau Pleine, the Wisconsin and the Mississippi: about 1,900 river miles.
Lakes on the way: Petenwell Lake, Lake Wisconsin, Lake Du Bay and Wisconsin River Flowage 4964.
1,610 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Johnson; river miles along the main stem, rounded.
