The Alcona 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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10° on Nov. 12, 2019, the coldest reading for this week of the year since 1971. Next is 13° in 2017.
Alcona’s center stands about 830 ft above sea level. Within three miles the land runs from 740 ft to 960 ft, a difference of 220 ft: rolling country. The highest named summit within 15 miles is Chin Whisker Hill, about 1,140 ft, 14 miles west-southwest.
Under the town center the state geologic map shows Antrim Shale (black-shale), from the Late Devonian, 359 to 384 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 36×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Black-shale. Age: Late Devonian, 359 to 384 million years old. About 10 mi of the line.
Shale. Age: Carboniferous, 324 to 359 million years old. About 8 mi of the line.
Shale. Age: Late Devonian, 359 to 384 million years old. About 0.6 mi of the line.
Black-shale. Age: Devonian to Carboniferous, 324 to 422 million years old. About 0.6 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 Alcona reaches Lake Huron by way of Pettis Creek, Sucker Creek, the Lower South Branch Thunder Bay and the Thunder Bay: about 55 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
Lake on the way: Hubbard Lake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alcona; river miles along the main stem, rounded.
Alcona has a warm-summer humid continental climate. Summer afternoons average 74° in August; winter nights fall to about 13° in January. A normal year brings about 52 inches of snow; with the rain, that comes to about 29 inches of water.
On November 14 Alcona normally reaches 42° and falls to 30°. The record high is 61°, in 2005; the record low 12°, in 2019. The most rain on this date, 0.32 in, fell in 2000.
Normals 1991–2020 and records since 1971 at Harrisville State Park, 13 miles southeast, 220 ft lower. NOAA, through RCC-ACIS.
