The Mertens 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.
Chance of showers
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3.74 inches of rain fell in two days, the most for this week of the year since records began in 1903. The next wettest, 2.79 inches, fell in 2004.
Mertens’s center stands about 540 ft above sea level. Within three miles the land runs from 480 ft to 600 ft, a difference of 120 ft: gently rolling country.
Under the town center the state geologic map shows Ozan Formation (claystone), from the Late Cretaceous, 66 to 72 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 47×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Claystone. Age: Late Cretaceous, 66 to 72 million years old. About 12 mi of the line.
Marlstone, chalk. Age: Late Cretaceous, 66 to 100 million years old. About 7 mi of the line.
Sandstone-mudstone. Age: Late Cretaceous, 66 to 72 million years old. About 2 mi of the line.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 1 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 Mertens reaches Galveston Bay and the Gulf of America by way of Richland Creek and the Trinity: about 400 river miles.
Lakes on the way: Woodlands Golf Course Lake and Navarro Mills Lake.
140 miles of the trip are on the Trinity.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mertens; river miles along the main stem, rounded.
Mertens has a humid subtropical climate. Summer afternoons average 97° in August; winter nights fall to about 34° in January. About 39 inches of rain fall in a normal year.
On November 14 Mertens normally reaches 69° and falls to 44°. The record high is 90°, in 1983; the record low 20°, in 1940. The most rain on this date, 1.10 in, fell in 1915.
Normals 1991–2020 and records since 1903 at Hillsboro, 13 miles west-southwest. NOAA, through RCC-ACIS.
