The Ontonagon 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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Ontonagon’s center stands about 640 ft above sea level. Within three miles the land runs from 590 ft to 810 ft, a difference of 220 ft: rolling country. The highest named summit within 15 miles is Adventure Mountain, about 1,480 ft, 13 miles east-southeast.
Under the town center the state geologic map shows Oronto Group; Freda Sandstone (shale, siltstone, arkose), from the Mesoproterozoic, 1 to 1.6 billion 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 23×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale, siltstone, arkose. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 11 mi of the line.
Conglomerate, sandstone. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 1 mi of the line.
Siltstone, shale, sandstone. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 0.3 mi of the line.
Andesite, basalt. Age: Mesoproterozoic, 1.1 to 1.1 billion 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 Ontonagon reaches Lake Superior by way of the Ontonagon: about 2 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Ontonagon; river miles along the main stem, rounded.
