The Amistad 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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90° on Nov. 11, 2006, the hottest reading for this week of the year since 1964. Next is 89° in 2002.
Amistad’s center stands about 1,180 ft above sea level. Within three miles the land runs from 1,070 ft to 1,360 ft, a difference of 290 ft: rolling country.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 33×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Late Cretaceous, 66 to 100 million years old. About 5 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 145 million years old. About 4 mi of the line.
Limestone, shale. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 4 mi of the line.
Gravel. Age: Late Pliocene to Pleistocene, less than 3.6 million years old. About 1 mi of the line.
Sand. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.8 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 Amistad reaches the Gulf of America by way of Amistad Reservoir and the Rio Grande: about 580 river miles.
Lakes on the way: Paz Ramirez Lake and Amistad Reservoir.
270 miles of the trip are on the Rio Grande.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Amistad; river miles along the main stem, rounded.
Amistad has a hot semi-arid climate. Summer afternoons average 97° in July; winter nights fall to about 40° in January. About 19 inches of rain fall in a normal year.
On November 14 Amistad normally reaches 71° and falls to 49°. The record high is 87°, in 2025; the record low 26°, in 2018. The most rain on this date, 0.55 in, fell in 1998.
Normals 1991–2020 and records since 1964 at Amistad Dam, 9 miles east-southeast. NOAA, through RCC-ACIS.
