Thursday, March 26, 2009

House Mountain Volcano with the Sedona Westerners

On March 25 the wind stopped blowing enough in northern Arizona so that 14 individuals plus myself ventured 3 miles on the Turkey Tank Trail to the top of the House Mountain volcano. This Miocene age (15 to 13 Ma) shield is "Sedona's volcano". I completed my Master's degree by completing a 75 square mile geologic map centered around the vent. It was an awesome project that yielded great rewards. Now, 21 years later, I still lead interested folks up to the crater and we discuss the geologic history along the way. Joan Steninger served as my "sweep" on the hike and provided me with these three pictures from our wonderful day! Thank you for the use of your photos Joan!

Here I am showing off the map that I completed back in 1988. It is vividly colored for a former museum exposition and these are not the normal colors that geologists use to portray rock outcrops. It does however, clearly show the central vent in the center of the map as a heart-shaped orange object. It's actually about a mile across in diameter on the landscape.

Here I am showing the group a stack of agglutinate scoria. What is agglutinate you ask? When House Mountain first erupted, the lave was highly charged with gas and so the lava blobs were thrown into the air as volcanic bombs. When these hit the ground they were still quite hot and they splattered on one another forming agglutinate. I had never noticed this particular outcrop close to where I always have lunch with geology groups and it just shows that even the "experts" are learning all of the time.

Our group is getting ready for lunch on the summit of House Mountain. Notice the red scoria (cinders) on the ground. After my thesis was completed, one of my advisors became so curious about this volcano that he undertook his own studies of the chemistry of the lava's. He discerned that when House Mountain first erupted, it built a cinder cone that was later buried by shield lava's. These outcrops here are from the early cinder cone.

I took a number of new photo's of rock samples on this hike and will use them in the new third edition of Sedona Through Time when it comes out at the end of this year!


  1. Cool hike! I certainly would have asked what agglutinate was! Good to know! Wish I lived closer so I could attend these sorts of things..thanks for posting!

  2. great photos wayne.

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