From University of Arizona (US) : “UArizona Geologists to ‘X-ray’ the Andes”

From University of Arizona (US)


Media contact
Daniel Stolte
Science Writer, University Communications

Researcher contact
Susan Beck
Department of Geosciences

A network of seismic stations poised to record images from deep underground will help scientists understand the mechanisms driving the formation of mountain ranges in unprecedented detail.

Andean Mountain range in Argentina showing the snow-capped peak of Aconcagua, the tallest mountain in the Americas, rising 22,837 feet above sea level. Credit: Peter DeCelles.

Led by geoscientists at the University of Arizona, an international research team will use data from earthquakes, geology and geochemistry to study, in greater detail than ever before, how mountain ranges are built.

Supported by a $3 million grant from the National Science Foundation (US), the project will shed light on how the Andes in South America formed, and produce a 3D model of mountain-building based on the Andes as a natural laboratory.

The project, which is part of the NSF Frontier Research in Earth Science program, is dubbed TANGO, which stands for Trans Andean Great Orogeny. At the heart of the project is one of the most extensive network of earthquake sensors-seismometers-to ever be installed in the Andes region of South America. Scientists will use seismic waves traveling through Earth’s interior from quakes around the globe to better understand the geologic processes underlying the formation of mountain ranges.

TANGO will focus specifically on the Andes from northern to southern Chile and in Argentina.

“TANGO is an excellent example of the type of international collaboration that characterizes the University of Arizona’s unique capacity to tackle the grand challenges of our time,” said University of Arizona President Robert C. Robbins. “Building on our strengths and ongoing research in the geosciences, our faculty laid the groundwork that allowed them to successfully assemble an international team to help us gain a better understanding of a natural process where there is still a lot to learn.”

Susan Beck, a UArizona professor of geosciences, will serve as TANGO’s lead principal investigator, with co-principal investigators Barbara Carrapa, Peter DeCelles, Mihai Ducea and Eric Kiser of the UArizona Department of Geosciences.

A major part of the TANGO project centers around seismic imaging, which works much like medical imaging such as CT scans, which use X-ray images to make tissues visible based on their densities. Just like bone and soft tissue show up as different features, geologic features beneath the Earth’s surface show up distinctly when geologists “X-ray” them by recording shockwaves from earthquakes as they travel through the Andes.

“Instead of sending X-rays through your head, we use seismic waves,” Beck said. “We deploy our instruments across a large area, and we wait for earthquakes to happen. We might take a year’s worth of data, from which we then assemble a tomographic image of what’s down there.”

While many of the processes involved in mountain-building — known as orogeny — are known to take place at the surface, other processes take place very deep inside the Earth, hidden from view. Seismic imaging allows researchers to probe the Earth’s interior down to about 700 miles, Beck said.

“Combined with geologic and geochemistry data from the rocks, we can understand how the Andes formed over the last 90 million years,” she said.

Along the western edge of South America, a chunk of ocean floor known as the Nazca plate pushes against its neighbor — the plate that contains the South American continent — at a rate of a little over 2 inches per year. This process, known as subduction, causes Earth’s crust to fold up, pushing up mountain peaks up to 20,000 feet in elevation.

“Subduction affects almost every aspect of our lives,” Beck said. “Think of it as a recycling program for Earth’s crust; it affects where mountains will rise up, where minerals and ores are formed, where tension is released as earthquakes and where the largest volcanic eruptions occur.”

Piecing Together ‘A Giant Puzzle’

Geologists still only have a vague idea of the details of mountain-building processes, Beck said, and TANGO is poised to fill some of the gaps.

“For example, we know that as one plate goes under the other, it causes earthquakes, it drags layers of rock down with it and causes volcanoes to erupt,” she said. “But what happens with that molten rock before it gets to the surface? How deep does the Nazca plate go before it gets assimilated into the mantle?”

The Andes serve as a giant natural laboratory to study the complex process involved in building a mountain range, Beck said.

“When you make mountains, rocks erode, and all that eroded rock has to go somewhere,” Beck said. “In a large mountain range like the Andes, that eroded material adds up.”

As debris from the eroding mountains accumulates in basins on the east side of the Andes, it creates a layered archive of time that “is amazing to unravel,” Beck said, but also presents geologists with head-scratchers.

The east face of Aconcagua clearly shows the layers of the lavas and volcanic deposits that make up the mountain. The large glacier on the northeast face is known as the Polish Glacier. Credit: Peter DeCelles.

“We have a decent understanding of the big picture, but we don’t really understand the dynamics of it in detail,” Beck said. “For example, we find deposits from those basins high up in the mountains, and we don’t really know how they ended up there, so it’s like a giant puzzle.”

Beck said she is excited about the seismic imaging component of TANGO.

“Each seismic wave has a travel time that we can measure,” she said. “The time it takes a seismic wave to get from the epicenter of an earthquake to our station depends on the materials it travels through at different speeds, and we can unravel that. For example, a seismic wave that goes through a magma body really slows down compared to a wave that doesn’t, and we will see that difference.”

To record thousands of earthquakes occurring in South America and around the globe, the team will install seismic stations across an area measuring about 800 miles by 400 miles. Deploying the technology in the field will involve many students from UArizona and partner institutions.

“Some stations are easy, as they are in readily accessible locations and we just need to dig a hole and insert the sensors,” Beck said, “but others are in very remote locations, at high elevations. Some seismic stations require building a vault, mounting solar panels and batteries so the seismic station can run for years.”

TANGO differs from similar efforts in scope and scale, Beck said.

“In a typical scenario, people would put these stations out for a month, pull them up and call it good, but we will be going into very remote areas, and we will have to deploy our instruments over many months to years. We look at this as our one-time chance to get the data that could help us answer these fundamental questions. It’s going to be a huge field effort.”

Since orogenic mechanisms are not unique to the Andes, TANGO will help scientists better understand tectonic processes in other areas as well. Beck said the Andes are a modern analog for what the western margin of North America looked like between 70 and 90 million years ago.

“Similar processes have happened through geologic time in many places throughout the world,” she said.

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As of 2019, the University of Arizona (US) enrolled 45,918 students in 19 separate colleges/schools, including the UArizona College of Medicine in Tucson and Phoenix and the James E. Rogers College of Law, and is affiliated with two academic medical centers (Banner – University Medical Center Tucson and Banner – University Medical Center Phoenix). UArizona is one of three universities governed by the Arizona Board of Regents. The university is part of the Association of American Universities and is the only member from Arizona, and also part of the Universities Research Association(US). The university is classified among “R1: Doctoral Universities – Very High Research Activity”.

Known as the Arizona Wildcats (often shortened to “Cats”), the UArizona’s intercollegiate athletic teams are members of the Pac-12 Conference of the NCAA. UArizona athletes have won national titles in several sports, most notably men’s basketball, baseball, and softball. The official colors of the university and its athletic teams are cardinal red and navy blue.

After the passage of the Morrill Land-Grant Act of 1862, the push for a university in Arizona grew. The Arizona Territory’s “Thieving Thirteenth” Legislature approved the UArizona in 1885 and selected the city of Tucson to receive the appropriation to build the university. Tucson hoped to receive the appropriation for the territory’s mental hospital, which carried a $100,000 allocation instead of the $25,000 allotted to the territory’s only university (Arizona State University(US) was also chartered in 1885, but it was created as Arizona’s normal school, and not a university). Flooding on the Salt River delayed Tucson’s legislators, and by they time they reached Prescott, back-room deals allocating the most desirable territorial institutions had been made. Tucson was largely disappointed with receiving what was viewed as an inferior prize.

With no parties willing to provide land for the new institution, the citizens of Tucson prepared to return the money to the Territorial Legislature until two gamblers and a saloon keeper decided to donate the land to build the school. Construction of Old Main, the first building on campus, began on October 27, 1887, and classes met for the first time in 1891 with 32 students in Old Main, which is still in use today. Because there were no high schools in Arizona Territory, the university maintained separate preparatory classes for the first 23 years of operation.


UArizona is classified among “R1: Doctoral Universities – Very high research activity”. UArizona is the fourth most awarded public university by National Aeronautics and Space Administration(US) for research. UArizona was awarded over $325 million for its Lunar and Planetary Laboratory (LPL) to lead NASA’s 2007–08 mission to Mars to explore the Martian Arctic, and $800 million for its OSIRIS-REx mission, the first in U.S. history to sample an asteroid.

The LPL’s work in the Cassini spacecraft orbit around Saturn is larger than any other university globally. The UArizona laboratory designed and operated the atmospheric radiation investigations and imaging on the probe. UArizona operates the HiRISE camera, a part of the Mars Reconnaissance Orbiter. While using the HiRISE camera in 2011, UArizona alumnus Lujendra Ojha and his team discovered proof of liquid water on the surface of Mars—a discovery confirmed by NASA in 2015. UArizona receives more NASA grants annually than the next nine top NASA/JPL-Caltech(US)-funded universities combined. As of March 2016, the UArizona’s Lunar and Planetary Laboratory is actively involved in ten spacecraft missions: Cassini VIMS; Grail; the HiRISE camera orbiting Mars; the Juno mission orbiting Jupiter; Lunar Reconnaissance Orbiter (LRO); Maven, which will explore Mars’ upper atmosphere and interactions with the sun; Solar Probe Plus, a historic mission into the Sun’s atmosphere for the first time; Rosetta’s VIRTIS; WISE; and OSIRIS-REx, the first U.S. sample-return mission to a near-earth asteroid, which launched on September 8, 2016.

UArizona students have been selected as Truman, Rhodes, Goldwater, and Fulbright Scholars. According to The Chronicle of Higher Education, UArizona is among the top 25 producers of Fulbright awards in the U.S.

UArizona is a member of the Association of Universities for Research in Astronomy(US), a consortium of institutions pursuing research in astronomy. The association operates observatories and telescopes, notably Kitt Peak National Observatory(US) just outside Tucson. Led by Roger Angel, researchers in the Steward Observatory Mirror Lab at UArizona are working in concert to build the world’s most advanced telescope. Known as the Giant Magellan Telescope(CL), it will produce images 10 times sharper than those from the Earth-orbiting Hubble Telescope.

Giant Magellan Telescope, 21 meters, to be at the NOIRLab(US) National Optical Astronomy Observatory(US) Carnegie Institution for Science’s(US) Las Campanas Observatory(CL), some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high.

The telescope is set to be completed in 2021. GMT will ultimately cost $1 billion. Researchers from at least nine institutions are working to secure the funding for the project. The telescope will include seven 18-ton mirrors capable of providing clear images of volcanoes and riverbeds on Mars and mountains on the moon at a rate 40 times faster than the world’s current large telescopes. The mirrors of the Giant Magellan Telescope will be built at UArizona and transported to a permanent mountaintop site in the Chilean Andes where the telescope will be constructed.

Reaching Mars in March 2006, the Mars Reconnaissance Orbiter contained the HiRISE camera, with Principal Investigator Alfred McEwen as the lead on the project. This National Aeronautics and Space Administration(US) mission to Mars carrying the UArizona-designed camera is capturing the highest-resolution images of the planet ever seen. The journey of the orbiter was 300 million miles. In August 2007, the UArizona, under the charge of Scientist Peter Smith, led the Phoenix Mars Mission, the first mission completely controlled by a university. Reaching the planet’s surface in May 2008, the mission’s purpose was to improve knowledge of the Martian Arctic. The Arizona Radio Observatory(US), a part of UArizona Department of Astronomy Steward Observatory(US), operates the Submillimeter Telescope on Mount Graham.

The National Science Foundation(US) funded the iPlant Collaborative in 2008 with a $50 million grant. In 2013, iPlant Collaborative received a $50 million renewal grant. Rebranded in late 2015 as “CyVerse”, the collaborative cloud-based data management platform is moving beyond life sciences to provide cloud-computing access across all scientific disciplines.
In June 2011, the university announced it would assume full ownership of the Biosphere 2 scientific research facility in Oracle, Arizona, north of Tucson, effective July 1. Biosphere 2 was constructed by private developers (funded mainly by Texas businessman and philanthropist Ed Bass) with its first closed system experiment commencing in 1991. The university had been the official management partner of the facility for research purposes since 2007.

U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.