The Clay 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.
Clay’s center stands about 950 ft above sea level. Within three miles the land runs from 750 ft to 1,650 ft, a difference of 900 ft: hilly country. The highest named summit within 15 miles is Butler Knob, about 2,340 ft, 8 miles north-northeast.
The section below crosses 15 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 11×. 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, conglomerate. Age: Carboniferous, 299 to 324 million years old. About 4 mi of the line.
Sandstone. Age: Carboniferous, 299 to 324 million years old. About 3 mi of the line.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 2 mi of the line.
Siltstone. Age: Late Devonian, 359 to 384 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.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 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. 9 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 Clay reaches Chesapeake Bay and the Atlantic Ocean by way of Spring Creek, Three Springs Creek, Aughwick Creek, the Juniata and the Susquehanna: about 190 river miles.
Lake on the way: Lake Aldred.
80 miles of the trip are on the Juniata.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Clay; river miles along the main stem, rounded.
Clay 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 Clay 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, 18 miles west-northwest, 520 ft higher. NOAA, through RCC-ACIS.
