The Logan 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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74° on Nov. 12, 1999, the hottest reading for this week of the year since 1941. Next is 70° in 1990.
Logan’s center stands about 4,250 ft above sea level. Within three miles the land runs from 4,070 ft to 4,720 ft, a difference of 650 ft: hilly country. The highest named summit within 15 miles is Little Round Mountain, about 5,570 ft, 10 miles east-northeast.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 11×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Siltstone, sedimentary-breccia, conglomerate. Age: Early Eocene to Early Miocene, 16 to 56 million years old. About 5 mi of the line.
Shale, limestone, sandstone. Age: Middle Cambrian to Cambrian, 487 to 521 million years old. About 4 mi of the line.
Age: Late Miocene to Holocene, less than 7.2 million years old. About 3 mi of the line.
Dolostone, limestone, sandstone. Age: Middle Mississippian to Permian, 252 to 347 million years old. About 2 mi of the line.
Sandstone, limestone, shale. Age: Middle Jurassic to Early Cretaceous, 100 to 172 million years old. About 2 mi of the line.
Age: Pleistocene to Holocene, less than 1.8 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. 5 smaller units along the line are not listed.
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 Logan reaches the Gulf of America by way of the Gallatin, the Missouri and the Mississippi: about 3,480 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Fort Peck and Lake Sharpe.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Logan; river miles along the main stem, rounded.
Logan has a warm-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 10° in January. About 13 inches of rain fall in a normal year.
On November 14 Logan normally reaches 42° and falls to 19°. The record high is 66°, in 1963; the record low −15°, in 1959. The most rain on this date, 0.45 in, fell in 1941.
Normals 1991–2020 and records since 1941 at Bozeman Gallatin Field Airport, 14 miles east-southeast, 180 ft higher. NOAA, through RCC-ACIS.
