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Van Tuyl Lecture: Brent Ward, Simon Fraser University
November 7 @ 4:00 pm - 5:00 pm
Brent Ward, Simon Fraser University
Berthoud 241, 4-5PM
Landslides, Geomorphic Evolution and Geoscience Outreach in Colca Valley, Peru
Abstract: Colca Valley, one of Peru’s top tourist destinations, comprises deep canyons with multiple terraces. Tectonism, volcanism and landslides have formed this stunning landscape, but also pose major hazards. A cooperative research venture – between Simon Fraser University’s Centre for Natural Hazards Research, the Peruvian Geological Survey (INGEMMET) and Université Clermont Auvergne – is investigating the Maca and Lari landslides and related aspects of the geomorphic evolution of Colca Valley. Knowledge being gained through this collaboration is fundamental to effective hazard and risk management in the valley, supports geoscience outreach to local communities and possibly be incorporated into existing Geopark displays.
We conducted a field-based textural, structural and stratigraphic study of Quaternary deposits to reconstruct the valley’s geomorphological evolution. We combined mangentostratigraphy, cosmogenic dating, tephrochronology, optically stimulated luminance dating (OSL), and radiocarbon dating to constrain the age and spatial relation of debris avalanches, lava flows and lacustrine sediments. The valley contains at least three levels of lake sediments spanning ~1.1 Ma that record impoundments by landslides or lava flows from the nearby Hualca Hualca stratavolcano. We gave particular attention to the stratigraphy of the active landslides affecting the towns of Maca and Lari. Both are large, hummocky rock avalanches deposited onto the middle and lowest lake terraces, respectively. Both have reactivated as complex failures due to undercutting of underlying lake sediments by Río Colca. Recent deformation involves the entire sequence and affects the towns. A 5.3 M earthquake on August 14, 2016 killed four people and exacerbated movement on both failures. Multicomponent monitoring by INGEMMET indicates increased movement correlates with high rainfall and seismic events.