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Tracking Flat Slabs in Colombia

Flat Slab
Unlike standard subduction, in which a tectonic plate descends beneath another plate into Earth, flat slab subduction is a process in which a tectonic plate descends to depths of about 30 to 60 miles ( ~50-100 kilometers, light blue, green, and beige) then flattens and travels horizontally for hundreds of miles before descending farther into Earth’s mantle. Image courtesy Lara Wagner, Carnegie Institution for Science

flat slab is a tectonic plate that does subduction a bit differently than usual. It descends to depths of about 30 to 60 miles before flattening out and traveling horizontally for hundreds of miles before descending farther into the Earth’s mantle. This is in contrast to standard subduction, which involves a plate diving directly beneath another plate.

A $2.7 million NSF-Frontiers of Earth Science grant has been awarded to a team of researchers including the Jackson School’s Brian Horton and Thorsten Becker to study an active flat slab in Colombia. The co-principal investigators include Lara Wagner of Carnegie Mellon University and Christy Till of Arizona State University.

Flat slabs traveling horizontally and directly beneath the overriding continents leads to extensive effects on the continental crust, including mountain building far from plate boundaries, ore formation and geochemical modifications that can affect the long-term stability of the overriding plate. Furthermore, large earthquakes within flat slabs, such as the magnitude 7.1 Mexico City earthquake that occurred in 2017 or the magnitude 8.0 earthquake in Peru that occurred in May 2019, can cause extensive damage in areas where earthquakes are uncommon and local communities less prepared.

Unlike previously studied flat slabs, the Colombian flat slab has broken into two parts, one of which has recently sunk back into the mantle to resume a normal subduction geometry. By comparing the still-existing flat slab region to the newly sunken flat slab region, the researchers will be able to study the initial migration and cessation of volcanism, the development of modern analogues to the Rocky Mountains (called basement cored uplifts), the formation of ore deposits, and ultimately, the return to normal arc volcanism — the complete flat slab cycle.

The grant will fund a 70-station, two-year seismic deployment across much of central Colombia, as well as an education and outreach program that will take teachers from Washington, D.C., Austin and Phoenix into the field, and help them prepare bilingual educational lessons, multimedia and web materials on the Earth sciences.