The St. Marys 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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75° on Nov. 11, 2020, the hottest reading for this week of the year since 1893. Next is 72° in 2012.
St. Marys’s center stands about 1,710 ft above sea level. Within three miles the land runs from 1,500 ft to 2,140 ft, a difference of 640 ft: hilly country. The highest named summit within 15 miles is North Fork Summit, about 2,370 ft, 6 miles north.
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 19×. 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: Devonian to Carboniferous, 324 to 422 million years old. About 11 mi of the line.
Sandstone, conglomerate. Age: Carboniferous, 299 to 324 million years old. About 7 mi of the line.
Sandstone. Age: Carboniferous, 299 to 324 million years old. About 5 mi of the line.
Sandstone, siltstone, shale. Age: Late Devonian, 359 to 384 million 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.
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.
St. Marys straddles the Eastern Continental Divide. Rain on the southwest side runs to the Gulf of America; most of the rest goes to Chesapeake Bay and the Atlantic Ocean.
From the center of town, a raindrop reaches Chesapeake Bay and the Atlantic Ocean by way of South Fork West Creek, West Creek, Driftwood Branch Sinnemahoning Creek, Bennett Branch Sinnemahoning Creek, Sinnemahoning Creek, the West Branch Susquehanna and the Susquehanna: about 300 river miles. One that lands on the southwest side reaches the Gulf of America by way of Silver Run, Elk Creek, the Clarion, the Allegheny, the Ohio and the Mississippi: about 2,140 river miles.
Lake on the way: Lake Aldred.
110 miles of the trip are on the West Branch Susquehanna.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of St. Marys; river miles along the main stem, rounded.
St. Marys has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 16° in January. A normal year brings about 53 inches of snow; with the rain, that comes to about 46 inches of water.
On November 14 St. Marys normally reaches 50° and falls to 30°. The record high is 68°, in 2010; the record low 7°, in 1996. The most rain on this date, 1.40 in, fell in 1972.
Normals 1991–2020 and records since 1893 at Ridgway, 12 miles west-southwest, 350 ft lower. NOAA, through RCC-ACIS.
