The Black Rock 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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Black Rock’s center stands about 6,450 ft above sea level. Within three miles the land runs from 6,300 ft to 7,070 ft, a difference of 770 ft: hilly country. The highest named summit within 15 miles is South Burned Timber Mountain, about 7,350 ft, 15 miles east-northeast.
Under the town center the state geologic map shows Chinle Group (sandstone, mudstone, conglomerate), from the Middle Triassic to Late Triassic, 202 to 247 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 18×. 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 0.1 million years old. About 9 mi of the line.
Sandstone, mudstone, conglomerate. Age: Middle Triassic to Late Triassic, 202 to 247 million years old. About 4 mi of the line.
Shale, limestone. Age: Late Cretaceous, 90 to 94 million years old. About 2 mi of the line.
Sandstone, shale. Age: Middle Jurassic, 164 to 175 million years old. About 2 mi of the line.
Andesite, basalt. Age: Pleistocene, 0.1 to 2.6 million years old. About 2 mi of the line.
Shale, sandstone. Age: Late Cretaceous, 84 to 90 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. 2 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 Black Rock reaches the Gulf of California by way of the Zu¿i, the Little Colorado and the Colorado: about 1,090 river miles.
Lakes on the way: Lake Mead, Lake Mohave and Lake Havasu.
290 miles of the trip are on the Colorado.
Often dry. About 30% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Black Rock; river miles along the main stem, rounded.
