Uneven Lanes

Last week I attended the Annual Meeting for the Association of Environmental & Engineering Geologists (AEG).  This year’s meeting was held in Salt Lake City, Utah, and was once again filled to the brim with events, meetings, and last minute preparations for my presentation.  Leading into the conference was a three day field trip centered around several of the National Parks in southern Utah, including Zion, Bryce Canyon, and Kolob Canyons (ok, that last one is technically part of Zion…but on the opposite corner of the park so I’m counting it). We also made several stopped on the routes to, between, and from the parks and Salt Lake City.

While I’m in post-conference catch-up mode, I thought one of our en-route stops would be a neat thing to share.  At this stop, we pulled our bus full of geologists off the beaten path to an abandoned housing development outside of Cedar City, UT.  The roads, sidewalks, and utilities had all been installed in 2009…practically brand new.  Yet, before they could begin construction on even one house, the whole project was scraped due to the appearance of large earth fissures, which made no bones about cutting right through the nice new asphalt and concrete.

Earth Fissure down the middle of an abandoned street. Outside Cedar City, UT (bag-o-chips for scale).

Displacements up to 7″ occurred all throughout the development.  This may not sound like much, but your typical car tires and house foundations certainly wouldn’t hold up to this kind of offsetting.

Large vertical displacement is observed throughout the area (pen for scale).

Here’s an aerial view from Google Earth. Unfortunately, this image is still from 2005 (prior to the roads being completed and subsequently abandoned), but if you look closely, you can see a rather long pre-existing earth fissure trending generally North-South just north of the unpaved roads.

Google Earth aerial view of the abandoned development (2005, prior to abandonment).

This is a great example of why geologists should be consulted prior to development in many areas of the country…even in topographically flat areas such as this one.  This problem is actually pretty common, but can you figure out why this happened?  Your main hints have already been given in the text and images above.  Share your thoughts and I’ll write a quick follow-up post, with the answer, next week!

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