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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.
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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.
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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!