The Mont Alto 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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1° on Nov. 16, 1908, the coldest reading for this week of the year since 1899. Next is 9° in 1933.
Mont Alto’s center stands about 880 ft above sea level. Within three miles the land runs from 730 ft to 1,920 ft, a difference of 1,190 ft: steep hill country. The highest named summit within 15 miles is Quirauk Mountain, about 2,150 ft, 10 miles south-southeast.
Under the town center the state geologic map shows Tomstown Formation (dolostone), from the Cambrian, 487 to 542 million years old.
The section below crosses 16 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 13×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Quartzite. Age: Cambrian, 487 to 542 million years old. About 4 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 3 mi of the line.
Limestone. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Graywacke. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Age: Precambrian. About 2 mi of the line.
Dolostone. Age: Cambrian, 487 to 542 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. 10 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 Mont Alto reaches Chesapeake Bay and the Atlantic Ocean by way of West Branch Antietam Creek, Antietam Creek and the Potomac: about 230 river miles.
180 miles of the trip are on the Potomac.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mont Alto; river miles along the main stem, rounded.
Mont Alto has a humid subtropical climate. Summer afternoons average 87° in July; winter nights fall to about 25° in January. About 36 inches of rain fall in a normal year.
On November 14 Mont Alto normally reaches 55° and falls to 38°. The record high is 75°, in 1989; the record low 10°, in 1920. The most rain on this date, 1.91 in, fell in 1995.
Normals 1991–2020 and records since 1899 from the Hagerstown Area threaded record (Hagerstown Regional Airport, 13 miles southwest, 190 ft lower). NOAA, through RCC-ACIS.
