The St. Ignace 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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St. Ignace’s center stands about 610 ft above sea level. Within three miles the land runs from 570 ft to 780 ft, a difference of 210 ft: rolling country. The highest named summit within 15 miles is Maple Hill, about 1,060 ft, 9 miles north-northwest.
Under the town center the state geologic map shows Point Aux Chenes Shale, from the Silurian, 422 to 428 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 45×. 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. Age: Silurian, 422 to 428 million years old. About 13 mi of the line.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 6 mi of the line.
Limestone. Age: Silurian, 428 to 445 million years old. About 3 mi of the line.
Dolostone. Age: Silurian, 428 to 445 million years old. About 2 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.
Rain that falls on St. Ignace runs straight into Lake Huron. 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 St. Ignace; river miles along the main stem, rounded.
