Geology of the National Parks Through Pictures - Sunset Crater

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You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Sunset Crater Volcano National Monument

View of the entrance sign with the volcano in the background.



The Sunset Crater Volcano is a volcano that last erupted about 1,000 years ago. It is a type of volcano known as a cinder cone, meaning that its eruptive material is small darkly colored rocks that pile up around the central vent. These rocks are typically a type of rock known as scoria, a vesicular (has lots of air holes in it), mafic (dark), volcanic rock. Since the last eruption was within the last 10,000 years, this volcano is still considered active by volcanologists.

Along with the cinder cone, there are also lots of lava flows within the park. Here you can see a lava flow that still looks as fresh as if it were a few years old. Since the desert environment does not get much rain, the volcanic rocks have a tendency to take a long time to break down, leaving these features for thousands of years.

Sunset Crater Volcano is part of a fissure eruption, which is a long crack in the ground that erupts like a volcano. Here the fissure runs along the left part of the photo ending at Sunset Crater Volcano in the middle of the photo.

Sunset Crater Volcano isn't the only volcano within the area or even within the park. There are lots of volcanos in this part of Arizona, mostly due to the plate tectonics of the area (as described in the Grand Canyon NP section above). The thinning of the crust due to the uplift of the plate causes weak spots in the crust where volcanic material can easily break through.