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      Close to Heaven… Down to Earth

 



 

Volcanic Plugs, Buttes and Cones
in Huerfano County, Colorado

Huerfano County has been described as “a broken, tilted and eroded plateau bridging
the mountains and the high plains.” Most of the tilting we see today occured during
the Sangre de Cristo upthrust, about 27 million years ago. That tilted the county
higher in the west and the easterly flow of the runoff caused the surface erosion
we see now. For whatever reason, though, the fault lines that allowed for the fault
block uplift we call the Sangre de Cristo’s run through western Huerfano County
but there was a break in the rock being pushed up from around the south side of
La Veta Pass to around the north side of Medano Pass.

In the gap between those two areas there was a bubble of magma pushing up and about
25 million years ago this solidified in open holes and vertical cracks in the sub-surface
of the Earth’s crust and formed the Spanish Peaks-White Mountains group (and the
associated radial dike system) and the Mt. Mestas-Rough Mountain-Silver Mountain-Sheep
Mountains group (and the associated radial dike system). The same flow of magma
also created Goemmer Butte, Gardner Butte, Huerfano Butte, Badito Cone, the Black
Hills, and the pile of rock atop Greenhorn Mountain (about 25 million years old
versus 1.7 billion years for the rock that makes up the lower parts of the mountain).

On his excellent website, Brian Penn goes into detail about the formation of most of these geological
features, complete with maps, photos, and timelines for the forming of certain features
and flows of magma (the East Spanish Peak was formed by two igneous intrusions…).

All of the buttes are volcanic plugs: the magma may have been flowing up a vent
towards the surface but it solidified in the form of a plug and that stopped the
motion. Goemmer Butte is in the valley between the West Spanish Peak and the Sangre
de Cristo’s. Gardner Butte is in the valley between the Mt. Mestas-Silver Mountain-Sheep
Mountains group and Greenhorn Mountain. To be different, Huerfano Butte is on the
edge of the high plains, southeast of the foot of Greenhorn Mountain, just below
the south shore of the Huerfano River. And Badito Cone is actually a conical high
point on a dike formation pointed directly uphill at the tops of Greenhorn Mountain.

In the old days, traveler’s on the Taos (or Trapper’s) Trail looked for Badito Cone
as a trail marker, that’s how the settlement at Badito happened: at the river right,
below the cone. Later, traveler’s on the San Luis Valley branch of the Santa Fe
Trail looked for Huerfano Butte as a trail marker. At one time, there was a busy
hotel, saloon and post office located beside the Huerfano River, just north of the
butte.

The Black Hills are an area where the magma flow didn’t solidify as dikes or as
plugs but as a series of ragged hills. To see what all of this really looks like,
take a trip some early morning: find your way to Greenhorn Mountain Road and follow
it to the end. You’ll be on a shelf there, looking out over all of western Huerfano
County. Sunrise is a great time to be there and watch the sun slowly creeping down
the faces of the Sangre de Cristo’s along the western horizon. Then it floods down
onto the more level surfaces of the county and, in the shadows, you can see the
folds and bends in the ground itself around the upthrust of the Mt. Mestas-Silver
Mountain-Sheeps group.