The Congress 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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Congress’s center stands about 3,050 ft above sea level. Within three miles the land runs from 2,820 ft to 3,720 ft, a difference of 900 ft: steep hill country. The highest named summit within 15 miles is Weaver Peak, about 6,520 ft, 12 miles north-northeast.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2 million years old. About 16 mi of the line.
Basalt. Age: Early Miocene to Late Miocene, 8 to 16 million years old. About 2 mi of the line.
Granite. Age: Mesoproterozoic, 1.4 to 1.4 billion years old. About 2 mi of the line.
Metasedimentary, schist. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 1 mi of the line.
Conglomerate, sandstone. Age: Early Miocene to Pleistocene, 2 to 16 million years old. About 1 mi of the line.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 0.9 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Congress reaches the Gulf of California by way of Sols Wash, the Hassayampa, the Gila and the Colorado: about 370 river miles.
170 miles of the trip are on the Gila.
Often dry. About 80% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Congress; river miles along the main stem, rounded.
