Cinder Cone in Northern Arizona

January 15, 2012

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Photographer: Phil Lachman
Summary Author: Phil Lachman

I photographed this beautiful cinder cone while touring the area north of Flagstaff, Arizona, in March and April 2010. It forms a striking pose looking over the surrounding grassy plains. The area that includes this cone and the more famous Sunset Crater is known as the San Francisco Volcanic Field. Eruptions in this field between the years 1040 and 1100 would have profoundly affected the way of life of the local inhabitants who witnessed these powerful geologic processes.

Cinder cones are made of pyroclastic material. The rock fragments, called cinders or scoria, accumulate around and downwind from a volcanic vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Handful of pumiceThe fragments are often glassy and contain numerous gas bubbles frozen into place as the magma exploded into the air and then cooled rapidly. This is how pumice, the floating rock, forms. The lower photo shows a handful of the scoria/cinders from Sunset Crater Volcano. If the eruption continues, the rock fragments form a steep conical hill. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet (300 m) or so above their surroundings. To the right and attached to the cone featured above is a lava flow that appears to have erupted through a breach on the side of the crater. Lava doesn't usually erupt over the top of a cinder cone as the rock fragments are too loosely packed to support the weight of the lava. Generally, it comes out of a breach or a vent in the side of the cone. Photo taken on April 14, 2010. Note that this cinder cone and the satellite image below (Earth Observatory) showing the SP crater were captured within three days of each other.

Photo Details: Top - Camera: FUJIFILM FinePix S7000; Focal Length: 12.0mm; Aperture: f/8.0; xposure Time: 0.0016 s (1/640); ISO equiv: 200; Software: Paint Shop Pro Photo 12.01. Bottom - Same except Focal Length: 7.8mm; Exposure Time: 0.0045 s (1/220).