The Hartly 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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16° on Nov. 17, 1933, the coldest reading for this week of the year since 1893. Next is 19° in 1920.
Hartly’s center stands about 80 ft above sea level. Within three miles the land runs from 50 ft to 140 ft, a difference of 90 ft: gently rolling country.
Under the town center the state geologic map shows Chesapeake Group (silt), from the Tertiary, 2.6 to 66 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Silt. Age: Tertiary, 2.6 to 66 million years old. About 15 mi of the line.
Gravel, sand. Age: Pleistocene, less than 2.6 million years old. About 9 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 Hartly reaches Chesapeake Bay and the Atlantic Ocean by way of Gravelly Run, Andover Branch and the Chester: about 55 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hartly; river miles along the main stem, rounded.
Hartly has a humid subtropical climate. Summer afternoons average 87° in July; winter nights fall to about 28° in January. A normal year brings about 13 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Hartly normally reaches 58° and falls to 40°. The record high is 76°, in 1955; the record low 19°, in 2019. The most rain on this date, 2.00 in, fell in 1972.
Normals 1991–2020 and records since 1893 at Dover, 11 miles east. NOAA, through RCC-ACIS.
