Hogbacks

San Rafael Swell and Hogbacks

On the Field Studies Fall 2011 class we went to explore the geology of the San Rafael Swell in Eastern Utah. The "swell" in this geological feature refers to dome which is pictured on the right- and on the San Rafael the west side of the dome  is at a gentler slope then the eastern side. As you drive through it you pass through a lot of time, because the closer to the center of the dome you get the older the layers get - it's like traveling through time in just a few short hours!

My favorite part about the trip was seeing the hogbacks on the eastern side of the dome. Many people believe that this geological formation is from the rock layers being pushed violently into the air from forces below (like earthquakes or the like) but those who know and understand more about geology understand that hogbacks don't have such a violent and sudden past.

Rather, this is from the dome itself and it's steeper eastern side.

As shown well in the picture to the left, you can see the angle of the rocks as they slop away from the anticline. These layers, like any other exposed formation, are then subjected to weathering. This lead to softer

shape, which leads to spectacular looking triangles that we call "flat irons". layers being eroded away and the more resist layers (like sandstone, etc) sticking around a little longer. As they erode away, little streams and rivers cut them into an ^ shape.

These are one of my favorite things in geology, I think they look so impressive and striking. And then knowing just how they were formed makes them even cooler - who needs dramatic and tragic earthquakes to make these things with you have geology to back you up?

~Tauni Sutherland