The Bonanza 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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Bonanza’s center stands about 9,590 ft above sea level. Within three miles the land runs from 9,130 ft to 11,990 ft, a difference of 2,860 ft: mountain country. The highest named summit within 15 miles is Mount Ouray, about 13,920 ft, 10 miles north-northwest.
Under the town center the state geologic map shows Ash-flow tuff of main volcanic sequence, from the Oligocene, 23 to 34 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 4×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Andesite. Age: Late Eocene to Early Oligocene, 30 to 35 million years old. About 11 mi of the line.
Andesite. Age: Oligocene, 23 to 34 million years old. About 3 mi of the line.
Volcanic. Age: Oligocene, 23 to 34 million years old. About 3 mi of the line.
Gravel, unconsolidated. Age: Pleistocene, less than 0.5 million years old. About 3 mi of the line.
Sandstone, shale. Age: Carboniferous, 299 to 324 million years old. About 1 mi of the line.
Gneiss. Age: Paleoproterozoic, 1.6 to 2.5 billion 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. 3 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 Bonanza reaches the closed basin of the San Luis Valley by way of Kerber Creek and San Luis Creek: about 85 river miles. The closed basin of the San Luis Valley has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
70 miles of the trip are on San Luis Creek.
Often dry. About 50% 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 Bonanza; river miles along the main stem, rounded.
