The Grandfalls 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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Grandfalls’s center stands about 2,430 ft above sea level. Within three miles the land runs from 2,420 ft to 2,520 ft, a difference of 100 ft: gently rolling country.
Under the town center the state geologic map shows Alluvium (fine-detrital, coarse-detrital), from the Holocene, less than 12,000 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 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.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 11 mi of the line.
Chemical. Age: Pleistocene to Holocene, less than 2.6 million years old. About 8 mi of the line.
Sand. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Sand. Age: Pleistocene to Holocene, less than 2.6 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.
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 Grandfalls reaches the Gulf of America by way of the Pecos and the Rio Grande: about 880 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 Grandfalls; river miles along the main stem, rounded.
