Sunday, May 02, 2010

Sinkholes in the Kaibab Limestone


Here at the AZGS, we get many hundreds of inquiries - from homebuyers, exploration companies, news outlets, rockhounds, other government agencies, and people just curious about the geology and geography of the state.

I got an email the other day from someone who had flown over Arizona on their way from California to Texas who was amazed by Meteor Crater but puzzled by large circular holes in the ground to the east. He asked if we could explain what he had seen.

AZGS Senior Geologist Jon Spencer suspects he was looking at a cluster of sinkholes produced where evaporates dissolved from the Supai Formation, leading to collapse in the overlying Kaibab Limestone [right].

[update 5-3-10, 11:30] AZGS geologist Steve Rauzi weighed in this morning, saying that the photo shows the McCauley Sinks south of Winslow along the western edge of Permian salt in the Holbrook basin. He also pointed me to a paper by James Neal describing these features in some detail.

Ref: Neal, James T., Robert Colpitts, and Kenneth S. Johnson, 1998, "Evaporite Karst in the Holbrook Basin, Arizona," in: Land Subsidence Case Studies and Current Research, Proceedings of the Dr. Joseph F. Poland Symposium, edited by James W. Borchers, Special Publication No. 8, Association of Engineering Geologists, pp 373-384.

9 comments:

  1. Great explanation! And thanks very much for taking the time to field questions like this one. There's no better way to encourage people to show some interest in the world around them than to share your staff's knowledge.

    You know, I'd also like to see a post about your five picks for overlooked spots throughout Arizona to see some unusual geological features. Just a thought!

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  2. I think that would be a great idea, Justin. I second the motion. People are always interested in anomalies.

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  3. Debbie10:01 AM

    The Central Arizona Geology Club took a field trip to the sinkhole area this spring led by Jim Neal and Paul Lindberg. Not only are there sinkholes in many places (not just at McCauley sinks) but there are areas of large, deep cracks and fissures. It is amazing geology.

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  4. Anonymous7:09 PM

    Famous Meteor Crater would be formed by that same process (sinkhole)?

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  5. Meteor Crater is well documented as having been formed by a meteor impact in the recent geologic past. The legendary geologist Gene Shoemaker resolved the debate over whether it might have been of volcanic origin, and as a result, is widely regarded as a founder of the field of planetary geology.

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  6. Anonymous8:32 PM

    Yes, I know and respect the work of Dr. Eugene Merle Shoemaker. There is another big sinkhole in the State of Oregon aproximately the same size of Meteor Crater but shallower. You can find it on Google Earth in coordinates: 43°24'40.30"N
    121°11'52.19"W

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  7. Anonymous1:33 AM

    About 15 miles south of Holbrook, AZ there are extremely deep fissures (referred to locally as "the Cracks") They range from just a few inches wide to several feet wide, but some seem to go down for a hundred feet. When you drop a rock in the crack you can hear it bouncing down the hole for an extremely long distance. Are these formed from seizmic activity?

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  8. Lee Allison10:45 AM

    This area has low historical seismicity. We think the fractures can be explained by the dissolution of the underlying salt, causing downdropping and folding of the overlying sediments. The folds cause extensional cracking across the surface.

    AZGS Open File Report 02-07, "A Review and Bibiography of Karst Features of the Colorado Plateau, Arizona" by Ray Harris, includes excellent descriptions and photos of the the fissures, cracks, fractures, and sinkholes of the region.

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  9. Anonymous8:04 PM

    Who does one ask what to do about a small (1 square foot and growing) front yard sinkhole in Scottsdale, AZ? The hole abuts a foundation wall so it is of concern.

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