Red Mountain cinder cone, USA

red-mountain-1The Red Mountain cinder cone near Flagstaff USA is a geology puzzle and has geological features including:

  • U shaped cinder cone creating a natural amphitheatre but created after the cone was formed
  • The cinder cone is not a normal symmetrical shape
  • Cinder strata radiates downwards away from a central high point in the U shape
  • Cinder cone and its rain water streams contains lots of pyroxene and amphibole minerals

Red Mountain ... is a volcanic cinder cone that rises 1,000 feet above the surrounding landscape. It is unusual in having the shape of a "U," open to the west, and in lacking the symmetrical shape of most cinder cones. In addition, a large natural amphitheater cuts into the cone's northeast flank. Erosional pillars called "hoodoos" decorate the amphitheater, and many dark mineral crystals erode out of its walls.

... The back wall of the amphitheater is a nearly vertical 800-foot cliff, which tapers off to the right and left. Truncated layers of volcanic cinders form ledges and color bands across the amphitheater walls.

A visitor standing in the center of the amphitheater, nearly surrounded by towering cliffs of cinders, might think that this is the center of the volcano, the location of the vent where molten rock (magma) was erupted. However, the actual center of eruption was over the back wall of the amphitheater, out of sight. The amphitheater is a geologic feature that formed after the eruption ended and continues to be enlarged by erosion today.
Red Mountain Volcano | U.S. Geological Survey

Cinder cone natural amphitheater

How was the geology unique cinder cone amphitheater formed when the rest of the volcanic cone remains? Why has it only occurred in Red Mountain on this one occasion?

The origin of the Red Mountain amphitheater is something of a geologic mystery. The truncated cinder layers exposed in the amphitheater walls are clear evidence that material has been removed. However, how this removal was accomplished is not entirely clear.

It seems unlikely that the entire amphitheater was created by water erosion, because there is so little surface area to catch rainwater and snowmelt and funnel it down channels to erode the side of the volcano.
Origin of the Amphitheater - Red Mountain Volcano | U.S. Geological Survey

By carefully measuring the orientation of cinder layers over all parts of Red Mountain, geologists have mapped a radial pattern of layers, dipping away from the middle of the U in all directions. At the amphitheater, all the exposed layers dip uniformly to the northeast. This pattern indicates that the vent is somewhere in the middle of the U and not at the amphitheater.
Red Mountain Cinder Cone - Red Mountain Volcano | U.S. Geological Survey

Red Mountain mineral stream

Red Mountain pyroxene and amphibole minerals cinder cone
If you are going on the Electric Universe geology tour after the EU 2016 conference then you will be visiting the Red Mountain volcano cinder cone.

On the 30 minute stroll up to and in the walls of the mysterious cone you will be able to see and perhaps pick up some minerals.

Roughly the last half of the foot trail follows a normally dry stream bed. The stream sand includes countless black shiny grains, a few as large as walnuts ... the abundant black grains at Red Mountain are crystals of minerals (pyroxene and amphibole) eroded from the volcano. A close look at the walls of the amphitheater will reveal crystals of these minerals still embedded in cinders, waiting to be plucked out by water and wind erosion.
Red Mountain Volcano | U.S. Geological Survey

San Francisco Volcanic Field

The San Francisco Volcanic Field is millions of years old, Red Mountain volcanic cone is only 3/4s of a million years old, yet its Red Mountain's cinder cone that is partially eroded or removed by some mysterious process?

Red Mountain is one of several hundred cinder cones within a swath of volcanic landscape that extends 50 miles eastward from Williams, Arizona, through Flagstaff to the canyon of the Little Colorado River. Geologists call this belt of volcanoes the San Francisco Volcanic Field, named for San Francisco Mountain, whose tallest peak is 12,633 feet above sea level, the highest elevation in Arizona. Red Mountain rises about 1,000 feet above the surrounding landscape, and its crest is at 7,965 feet elevation. The San Francisco Volcanic Field has been active for about 6 million years, and Red Mountain is roughly 740,000 years old.

Red Mountain is unusual in that its internal structure is exposed. This is not the case at most cinder cones in the San Francisco Volcanic Field, because erosion has not had enough time to expose their internal features.
San Francisco Volcanic Field - Red Mountain Volcano | U.S. Geological Survey

More images of Red Mountains cinder cone geology