This volcanic cinder cone with summit crater was formed just before
1100 AD. Its upper portion is colored as if by a sunset. Sunset Crater
appeared when molten rock was ejected into the air from a small crack in the
Earth's crust. When this material fell to the ground, it was already solid
and came down as large bombs and smaller cinders. This volcanic activity
continued over 200 years building and re-shaping the cone and eventually
creating a 1,000-foot cinder cone volcano around the vent. An 800 square
mile radius was dusted with ash from this volcano. Lava flowed from the
fissure both in 1064 and again in 1180. Over time new gas vents opened up
forming spatter cones around the main cinder cone. In a final burst of
activity, around 1250, lava containing iron and sulfur shot out of the vent.
This lava then oxidized red and yellow, these colors painting the crater
with a permanent "sunset" so bright that it appears still to glow from
intense inner heat.
Proclaimed May 26, 1930, as Sunset Crater National Monument
Acreage 3,040 all federal land.
Source: U.S. National Park Service
For more information:
Sunset Crater Volcano National Monument
Rt. 3, Box 149
Flagstaff, AZ 86004
520-526-0502
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