The Manassas 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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89° on Nov. 17, 1978, the hottest reading for this week of the year since 1904. Next is 88° in 1989.
Manassas’s center stands about 220 ft above sea level. Within three miles the land runs from 140 ft to 270 ft, a difference of 130 ft: gently rolling country.
Under the town center the state geologic map shows Pleistocene-Pliocene sands and gravels (sand, gravel), from the Pliocene to Pleistocene, less than 5.3 million years old.
The section below crosses 3 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.
Sand, gravel. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 12 mi of the line.
Sandstone, claystone. Age: Tertiary Neogene, 2.6 to 23 million years old. About 12 mi of the line.
Sand. Age: Quaternary, less than 2.6 million years old. About 0.5 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 Manassas reaches the Atlantic Ocean by way of Billy Fork Creek, Bull Creek, the Canoochee and the Ogeechee: about 100 river miles.
55 miles of the trip are on the Canoochee.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Manassas; river miles along the main stem, rounded.
Manassas has a humid subtropical climate. Summer afternoons average 92° in July; winter nights fall to about 37° in January. About 50 inches of rain fall in a normal year.
On November 14 Manassas normally reaches 70° and falls to 46°. The record high is 85°, in 1916; the record low 29°, in 1906. The most rain on this date, 1.45 in, fell in 2008.
Normals 1991–2020 and records since 1904 at Glennville 3 NW, 13 miles south-southeast. NOAA, through RCC-ACIS.
