Saturday, May 06, 2017

Geology in the Wild - Roadside Faults

While traveling home a couple of years ago, I happened to notice some nice faults along the side of the road. So, like any good geologist, I got out to take a few pictures.

The location is in Utah, within the Eocene Green River Formation east of the Tie Fork Rest Area between Price and Provo along Route 6. It's the fancy newish rest area that has a bunch of train displays.

The image below was taken along Route 6 facing north, with the west to the left and east to the right. You can get a pretty good view of it within Google Street View Here.

West                                                                                                                                      East

Taking a closer look at the western fault above.

And an even closer look with the fault highlighter. The beds show significant offset by matching up that double bed located just above the arrows in the image below.
 This type of fault is what is known as a Normal Fault, as illustrated in the image below. It results from extensional forces where each side of the fault are moving away from each other. A Reverse Fault would be where the two blocks are being pushed towards each other.

Looking at the eastern portion of the top image.

We can see there are two, nearly vertical, faults lying very close to each other.

The bend in the fault line above is just due to the degree of erosion revealing the fault at a weird angle and also the perspective from which I am viewing the fault. In actuality, the fault is not bent like that.

Both of these faults are also Normal Faults because of the same extensional activity as to the west. This makes sense because if the fault to the west resulted from extensional activity, it would be highly likely the entire area, if not the region, had undergone extensional pressures. This means that these couple of faults here would probably not be the only normal faults in the area and there are  more normal faults spread throughout the area and/or region.

This is what is known as a scientific hypothesis. We looked the available data on the region and came up with a testable hypothesis based on it.

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