The Monrovia 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.
Monrovia’s center stands about 430 ft above sea level. Within three miles the land runs from 370 ft to 680 ft, a difference of 310 ft: rolling country. The highest named summit within 15 miles is High Knob, about 1,560 ft, 13 miles west-northwest.
Under the town center the state geologic map shows Sams Creek Metabasalt, from the Proterozoic, 542 to 2,500 million years old.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 31×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mica-schist, quartzite. Age: Proterozoic, 542 to 2,500 million years old. About 6 mi of the line.
Limestone. Age: Cambrian, 487 to 542 million years old. About 4 mi of the line.
Phyllite, metasiltstone. 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 3 mi of the line.
Phyllite. Age: Proterozoic, 542 to 2,500 million years old. About 2 mi of the line.
Metabasalt. 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. 5 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 Monrovia reaches Chesapeake Bay and the Atlantic Ocean by way of 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 Monrovia; river miles along the main stem, rounded.
Monrovia 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 Monrovia 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, 8 miles south-southeast, 270 ft higher. NOAA, through RCC-ACIS.
