Submitted by Ben Surpless (re-posted from: http://keckutah.blogspot.com/)
How Many Rocks Can You Measure?
We’ve been out here for eleven days. Surely we’ve seen every single rock out here by now, right? Well, sometimes it feels like it, but around each corner, there’s always a new rock to sample. Still, you might be wondering, “what have we accomplished after all this time?”
Let’s start with the basic workflow of our field days. Most of our mornings are spent hiking out to cliff-like exposures of fractured sandstone. Once we’ve arrived, we set to work: starting from one end of each cliff, we stretch a long tape measure from one end of the exposed rock to the other, in order to measure how close each fracture is from one another. This is a bit trickier than it sounds, since there are often many fractures, each angled all different ways, amid bushes, trees, cacti, mountain lion dens, snake holes, and boulders. In addition to this awkward dance with the tape measure, we also record the dip and dip-direction of each fracture using a Brunton (pronounced with a heavy German accent, as Brrruhntun) geological field compass . The dip is simply the angle of the fracture in comparison to a horizontal plane. The dip-direction is just the compass direction in which the angled surface of the fracture faces. So, to record each fracture, we have the awkward tape dance, then we have to scramble up and down the slopes in order to find good surfaces to measure with a Brunton compass. All the while, we have to record the measurements we’ve obtained, of which there are many (many, many) in a little, pretty, yellow field notebook.
Most of our time in the field is spent this way, so that by the end of our time here, we will have mapped out several cliffs between fault segments in several different field regions. The idea is to digitize and plot the data, in order to see how the intensity, or the number of fractures, varies as you move closer to the main segment of the Sevier fault. Because fractures and faults are generated by stresses in the earth, we can use these data to document how the stress field varied over time as the fault system evolved.
But Hasn’t This All Been Done Before?
The Sevier fault has been studied by a few other geologists, whom we have researched and cited in preparation of our own work. But, an in-depth analysis of the transfer zone (the fractured areas between main fault segments) is ours for the taking. As such, we are all excited to start really looking at our data. Now that we’ve cataloged over 325 individual large-scale fractures on the ground and from the air (using the drone), our field time is almost up. For the next (and last) one-and-a-half days in the field, we will just be finishing up sample collection and drone work. Then, we will really dive into the data, looking at what we have and what sort of questions we might be able to propose and answer with all of the fieldwork.
Field Tip of the Day:
“Beautiful Breakfast” -Waking up at sunrise, to go into the field, can be very difficult. But, it is a well-documented fact that a good breakfast can make the process much easier. Unfortunately, when it’s early and you’re tired, even making breakfast can be too much to handle. Therefore, you might as well just give up and have breakfast for dinner. We’ve used this trick several times ourselves, and the result is both a delicious dinner and a pre-made breakfast for the next day.