The Jamestown 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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70° on Nov. 17, 2016, the hottest reading for this week of the year since 1978. Next is 67° in 2005.
Jamestown’s center stands about 7,020 ft above sea level. Within three miles the land runs from 6,510 ft to 8,790 ft, a difference of 2,280 ft: mountain country. The highest named summit within 15 miles is Mount Meeker, about 13,840 ft, 15 miles northwest.
Under the town center the state geologic map shows Laramide intrusive rocks (granitic, dioritic), from the Late Cretaceous to Middle Eocene, 40 to 72 million years old.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 3×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Alkali-feldspar-granite, granite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 7 mi of the line.
Biotite-gneiss, schist, migmatite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 5 mi of the line.
Granitic, dioritic. Age: Late Cretaceous to Middle Eocene, 40 to 72 million years old. About 2 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 1 mi of the line.
Granite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 6 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 Jamestown reaches the Gulf of America by way of Little James Creek, Left Hand Creek, Saint Vrain Creek, the South Platte, the Platte, the Missouri and the Mississippi: about 2,390 river miles.
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 Jamestown; river miles along the main stem, rounded.
Jamestown has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 17° in January. A normal year brings about 99 inches of snow; with the rain, that comes to about 20 inches of water.
Normals 1991–2020 and records since 1978 at Gross Reservoir, 13 miles south, 140 ft lower. NOAA, through RCC-ACIS.
