An article about the use of drones to study the Sevier fault was recently featured on the Texas Public Radio website. The article, which also includes an audio recording, describes research by Project Director Ben Surpless (Trinity University) and four Keck Consortium REU students to construct 3D models of the Sevier fault system in southern Utah.
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.
Have you ever wondered what it would be like to be able to fly? Well, occasionally, us geology students find ourselves staring out of a window, asking ourselves, “What do these rocks look like to the birds?”
Today, we got to find out. With Ben piloting and the rest of us monitoring and taking notes, we recorded lots of aerial video from a drone. Besides the fact that the clips were just down-right cool looking, they also served a scientific purpose. After processing the video, we should be able to create a 3-dimensional computer model of the fractures exposed in the rocks. This data collection and processing workflow is at the cutting-edge of geology tech; people have explored similar “structure-from-motion” technology, but so far, it has not been extensively used. Essentially, we undergraduate students are getting involved in high-level research with amazing technology in a geologically significant region; we are lucky.
Taylor Teams Up
And so, we spent the day split into two teams. While one group flew the drone, the other group hiked out to the cliffs on the opposite side of the canyon, taking reconnaissance notes. While all of this was going on, a visitor from Trinity University joined us in the field. Taylor Stakes, from the marketing team at Trinity, was dispatched to record our work, so he trogged along-side us, snapping pics and filming us working. The entire day was spent in this way. Afterwards, in camp, Taylor joined us for a delicious pasta dinner. As the pasta roiled and broiled, we all received a structural geology lesson from Ben. We learned all about the nuances of geologic terms, which tend to be extremely specific, scientific, and precise. Hopefully, tomorrow, we can use some of these new terms in the field, as we examine our next site.
Field Tip of the Day:
“Remove Before Flight”- Drones are sensitive pieces of equipment, so make sure that when you chuck them as hard as you can, you aim well. You might only get once chance at a good take-off.
This morning, our fieldwork began as usual, but quickly became something more magical. After picking up where we left off yesterday, our group quickly began to experience what others come from all around the world to see: true slot canyons. In fact, Utah is famous for its slot canyons and there are over 1,000 slot canyons in the state, as well as the world’s longest known slot canyon (which extends into Arizona).
Geologically, these narrow, tall canyons are formed when rainwater, running through a set of fractures in the rock, erodes downward over time, causing the slot to deepen without growing much in width.
The slot we entered is an up-drainage feature of Red Hollow Canyon, so we are able to continue taking fracture measurements inside the canyon walls. The slot itself extends for about 900 feet into the bright red Navajo sandstone, before coming to a 20 foot tall vertical cliff; frayed rope is the only way up. Since taking measurements is tedious and slow, it took us several hours to walk these 900 feet. Then, once we examined the sketchy rope, we declared it impassible and decided to have lunch instead.
Everyone Loves Lunch:
Field lunches are quite possibly the most exciting thing a young geologist can do; not only does lunch mean a chance to eat Oreos and Nutter-butter cookies, but it also gives us students a chance to grill Ben with endless geology-related questions. At the beginning of “let’s all ask Ben tough questions” time, we give him some easy ones, such as: “Why do most of these fractures propagate in a similar orientation?” Next, and before Ben has time to eat much of his lunch, we start asking the harder questions, such as: “How might an in-depth analysis of slickenlines be used for characterizing original stress fields?” So, basically, we try to outpace his Geology knowledge; we always fail to do so. Finally, by the end of lunch, the questions tend to become more metaphysical in nature: “Ben, how would you know when you’ve found true happiness?” Still, Ben is always ready with an answer. For us students, working under Ben’s guidance is a pleasure, not only because of the depth of his field-related knowledge, but also because he sometimes seems just like one of us. He is one of the most personable and youthful teachers you’ll ever meet; sometimes he seems just as eager as the rest of us to scramble up a crumbling cliff simply for the fun of it.
There’s Always a New Problem:
After lunch, Ben decided it was time to call it quits. By then, we had finished mapping all of the accessible fractures, so we returned to the field vehicle and drove to a new location, in order to scout it out. As it turned out, the road we had planned to used to access the Elkheart Cliffs was fenced-off, so we spent the evening in camp trying to find a workaround.
Field Tip of the Day:
“Canyon Connections” -when you and your friends venture deep into a slot canyon, it can be hard to see one another. So, instead of relying on visual communication, try playing some 1970’s disco music. This way, as long as the last person in your group can hear well enough to sing along, you know your entire group is near one another.
In order to understand how earthquakes propagate and fractures form in rocks, geologists like us analyze these features in the field. Here in southern Utah, there is spectacular exposure of fractures associated with a major fault system. This area affords our research squad the perfect opportunity to document these fractures, so that we can better understand how rocks behave under stress.
So why does anyone care?
Fractures associated with major faults can be used to better understand the size and distribution of earthquakes. In addition, fractures in rocks increase the flow of fluids like water, oil and natural gas in the Earth. Furthermore, where water circulates through fractures, deep in the Earth, its temperature increases and may return energy to the surface – yay geothermal energy!
What we’ve done…so far:
Our research is looking at how stress associated with major fault zones, such as the Sevier fault here in southern Utah, impacts the adjacent rocks. We have been spending our first couple days in the field measuring the distance between fractures and characterizing their orientation relative to one another. We have all had great time climbing rocks, smashing poorly cemented sandstones for scientific inquiry and sliding down Jurassic-aged sand dunes.
Tip of the day: “Boots, not Butt!” -when sliding down a steep slope, be sure to slide on your boot soles, not your pants; the friction produced during a controlled slide is easily enough to rip a pair of field pants and expose your field tighty-whities.