November 16, 2023
In the Field: Tracking seismic clues in one of the driest places on Earth
UW doctoral student Tamara Aránguiz-Rago collects rock samples on the hills next to a fault in Chile’s Atacama Desert for a pilot study in September 2022. This month she will collect more data to try to reconstruct the history of the formation of these mountains.Emma Heitmann/University of Washington
Unlike the Pacific Northwest, the Atacama Desert in Chile experiences very little rain. But the two regions are both seismically active. Faults in the Atacama Desert are slowly sliding past each other in a way similar to the Seattle Fault in Puget Sound and the San Andreas Fault in California. The Atacama Desert’s lack of rain makes it easier to see how those gradual movements shape the landscape over time.
Alison Duvall, a University of Washington associate professor of Earth and space sciences, and doctoral student Tamara Aránguiz-Rago will travel to Chile this month to study landscapes developed along these types of faults. Duvall has previously studied historic landslides at the site of the rainfall-triggered Oso mudslide and how rainfall, earthquake and landslide risks combine in Oregon.
UW News asked the two geophysicists about their upcoming trip as part of a new series, “In the Field,” highlighting UW field research.
Where are you going, and when?
Tamara Aránguiz-Rago: We will visit the Salar Grande, in the hyper-arid, or dry, core of the Atacama Desert in Northern Chile. The Salar is a dry lakebed that contains economic resources, in the form of salt, that is extracted from the basin and then exported around the world. We’ll be there Nov. 19-25.
We’re interested in this area because it’s extremely dry and has active faults slicing through it. Only a few places on Earth register such low rates of precipitation, offering a landscape that stores climate and tectonic variations from the past 50 million years. At our field site, there are places that haven’t seen a drop of rain in 500 years!
As a result, this is one of the best places on Earth to study how landscapes respond to earthquakes and plate tectonics under hyper-arid conditions. Dry conditions slow down erosion and help preserve landscape form and enable us to observe processes, like tectonic processes, that modify the surface from deeper down.
The Atacama Desert in September 2022. The flat strip of land in the middle is not a human-built road but a strike-slip fault, where two blocks slowly slide past each other. Researchers will travel to the site again this month to learn more about these types of faults.Tamara Aránguiz-Rago/University of Washington
Have you visited this field site before?
TA: I visited this site last fall with Emma Heitmann, another doctoral student in the Department of Earth & Space Sciences.
Alison Duvall: This will be my first time to this site, to Chile and to South America.
What do you hope to learn there?
AD: We want to learn more about the dynamics of slow faults that move laterally — strike-slip faults, similar to the San Andreas Fault in California — and how these dynamics control the shape of the landscape. In wet places, it’s hard to isolate faults’ effects on the landscape since water is the main agent driving erosion. What we observe on the surface in other places is a combination of tectonics and surface processes. However, thanks to the aridity of this place, it is easier to be confident about what is changing the landscape.
We’re also interested in how this landscape has shifted with a changing climate. This place was wetter in the past, and there is evidence of climate change happening to make the region hyper-arid. So we are also studying how the landscape has adapted to that change.
What’s something that you enjoy about this field work — especially something that might not occur to most people?
TA: There is a really special feeling when you’re in the driest place on Earth. It almost feels like you’re on a different planet. You don’t see any signs of life — no water, no animals, no plants — but it’s just amazing to feel that nothingness.
Changes in the landscape are so slow that when you visit the site, you know that each step you make, or any perturbation we make to collect our samples, can be one of the biggest modifications to the landscape in hundreds of years.
University of Washington doctoral student Emma Heitmann stands at the bottom of one of the biggest paleochannels in the study area in September 2022. The size of the rocks in the channel provides researchers with information about past wet events that have interrupted the current very dry climate.Tamara Aránguiz-Rago/University of Washington
Anything you’d like to add?
AD: I’m super excited to get to this incredible field site and spend time with Tamara studying it. We have done field work together in New Zealand, and I have done decades’ worth of field work in many different geomorphic settings, but never in a hyper-arid landscape like this one. I can’t wait to see what we find!
Tag(s): Alison Duvall • College of the Environment • Department of Earth and Space Sciences • earthquakes & seismology • geology • In the Field
