The Green Valley 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. 16, 1996, the coldest reading for this week of the year since 1993. Next is 18° in 2017.
Green Valley’s center stands about 660 ft above sea level. Within three miles the land runs from 430 ft to 810 ft, a difference of 380 ft: rolling country. The highest named summit within 15 miles is Sugar Loaf Mountain, about 1,270 ft, 10 miles west-southwest.
Under the town center the state geologic map shows Marburg Schist (mica-schist, quartzite), from the Proterozoic, 542 to 2,500 million years old.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 24×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Phyllite. Age: Proterozoic, 542 to 2,500 million years old. About 4 mi of the line.
Muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 4 mi of the line.
Limestone. Age: Cambrian, 487 to 542 million years old. About 3 mi of the line.
Phyllite. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Mica-schist, quartzite. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Phyllite, metasiltstone. Age: Proterozoic, 542 to 2,500 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. 4 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 Green Valley reaches Chesapeake Bay and the Atlantic Ocean by way of Church Branch, Bush Creek, the Monocacy and the Potomac: about 180 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Green Valley; river miles along the main stem, rounded.
Green Valley has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 25° in January. A normal year brings about 31 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Green Valley normally reaches 54° and falls to 37°. The record high is 74°, in 1993; the record low 22°, in 2019. The most rain on this date, 1.90 in, fell in 1995.
Normals 1991–2020 and records since 1993 at Damascus 3 SSW, 5 miles south. NOAA, through RCC-ACIS.
