The Alamo 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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Alamo’s center stands about 6,240 ft above sea level. Within three miles the land runs from 6,030 ft to 6,530 ft, a difference of 500 ft: hilly country. The highest named summit within 15 miles is Blue Mesa, about 8,540 ft, 12 miles west.
Under the town center the state geologic map shows Crevasse Canyon Formation (shale, sandstone), from the Late Cretaceous, 84 to 90 million years old.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Unconsolidated. Age: Pleistocene to Holocene, less than 2.6 million years old. About 5 mi of the line.
Shale, sandstone. Age: Late Cretaceous, 84 to 90 million years old. About 4 mi of the line.
Sandstone. Age: Late Cretaceous, 90 to 94 million years old. About 3 mi of the line.
Sandstone, mudstone, conglomerate. Age: Middle Triassic to Late Triassic, 202 to 247 million years old. About 3 mi of the line.
Shale, sandstone. Age: Late Cretaceous, 94 to 100 million years old. About 2 mi of the line.
Sandstone, shale. Age: Late Cretaceous, 90 to 94 million 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. 6 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 Alamo reaches the Gulf of America by way of the Rio Salado and the Rio Grande: about 1,540 river miles.
Lakes on the way: Paz Ramirez Lake, Amistad Reservoir, Elephant Butte Reservoir and Caballo Reservoir.
760 miles of the trip are on the Rio Grande.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alamo; river miles along the main stem, rounded.
