The Greenfield 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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11° on Nov. 14, 1986, the coldest reading for this week of the year since 1948. Next is 12° in 1959.
Greenfield’s center stands about 1,520 ft above sea level. Within three miles the land runs from 1,190 ft to 2,860 ft, a difference of 1,670 ft: steep hill country. The highest named summit within 15 miles is Blue Knob, about 3,140 ft, 3 miles west-southwest.
Under the town center the state geologic map shows Catskill Formation (sandstone, siltstone, shale), from the Late Devonian, 359 to 384 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 10×. 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: Late Devonian, 359 to 384 million years old. About 4 mi of the line.
Sandstone. Age: Carboniferous, 324 to 359 million years old. About 4 mi of the line.
Sandstone, shale. Age: Devonian to Carboniferous, 324 to 422 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Carboniferous, 299 to 324 million years old. About 2 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Siltstone, shale. Age: Late Devonian, 359 to 384 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 Greenfield reaches Chesapeake Bay and the Atlantic Ocean by way of South Poplar Run, the Frankstown Branch Juniata, the Juniata and the Susquehanna: about 240 river miles.
Lake on the way: Lake Aldred.
100 miles of the trip are on the Juniata.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Greenfield; river miles along the main stem, rounded.
Greenfield has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 21° in January. About 37 inches of rain fall in a normal year.
On November 14 Greenfield normally reaches 51° and falls to 34°. The record high is 73°, in 1993; the record low 11°, in 1986. The most rain on this date, 2.25 in, fell in 1972.
Normals 1991–2020 and records since 1948 at Altoona Blair County Airport, 10 miles east. NOAA, through RCC-ACIS.
