The Orrock 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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Showers likely
74° on Nov. 13, 1999, the hottest reading for this week of the year since 1959. Next is 69° in 1990.
Orrock’s center stands about 990 ft above sea level. Within three miles the land runs from 950 ft to 1,010 ft, a difference of 60 ft: gently rolling country.
Under the town center the state geologic map shows Middle and Upper Cambrian (sandstone, siltstone, shale), from the Middle Cambrian to Cambrian, 487 to 521 million years old.
The section below crosses 5 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.
Sandstone, siltstone, shale. Age: Middle Cambrian to Cambrian, 487 to 521 million years old. About 18 mi of the line.
Granitic. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 4 mi of the line.
Siltstone, graywacke, slate. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 0.9 mi of the line.
Volcanic, sedimentary, hypabyssal. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 0.5 mi of the line.
Sandstone, siltstone, shale. Age: Cambrian, 487 to 497 million years old. About 0.4 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 Orrock reaches the Gulf of America by way of the Elk River and the Mississippi: about 1,880 river miles.
Lake on the way: Lake Pepin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Orrock; river miles along the main stem, rounded.
Orrock has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 4° in January. A normal year brings about 49 inches of snow; with the rain, that comes to about 31 inches of water.
On November 14 Orrock normally reaches 41° and falls to 24°. The record high is 69°, in 1990; the record low −3°, in 2014. The most rain on this date, 0.52 in, fell in 2010.
Normals 1991–2020 and records since 1959 at Santiago 3 E, 7 miles north. NOAA, through RCC-ACIS.
