The Sullivan 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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66° on Nov. 15, 1939, the hottest reading for this week of the year since 1893. Next is 66° in 2005.
Sullivan’s center stands about 830 ft above sea level. Within three miles the land runs from 810 ft to 840 ft, a difference of 30 ft: nearly flat ground.
Under the town center the state geologic map shows Upper Ordovician (limestone, dolostone), from the Late Ordovician, 445 to 459 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 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone, dolostone. Age: Late Ordovician, 445 to 459 million years old. About 9 mi of the line.
Granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 8 mi of the line.
Shale, sandstone. Age: Ordovician, 445 to 487 million years old. About 5 mi of the line.
Limestone, dolostone. Age: Ordovician, 445 to 487 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.
A raindrop that lands in Sullivan reaches Hudson Bay by way of Grand Marais Creek, the Red River of the North and the Nelson: about 950 river miles. Past the border it runs north through Canada to Hudson Bay.
Lake on the way: Lake Winnipeg.
400 miles of the trip are on the Nelson.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sullivan; river miles along the main stem, rounded.
Sullivan has a warm-summer humid continental climate. Summer afternoons average 80° in July; winter nights fall to about −1° in January. A normal year brings about 49 inches of snow; with the rain, that comes to about 23 inches of water.
On November 14 Sullivan normally reaches 36° and falls to 20°. The record high is 62°, in 2025; the record low −17°, in 1919. The most rain on this date, 1.09 in, fell in 1944.
Normals 1991–2020 and records since 1893 at Grand Forks University (Nws), 9 miles west-southwest. NOAA, through RCC-ACIS.
