Nature and mechanics of slope instability at Pacaya Volcano

Author

Lauren Schaefer, Michigan Technological UniversityFollow

Date of Award

2016

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Geological Engineering (PhD)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Thomas Oommen

Committee Member 1

Yan Lavallée

Committee Member 2

Zhong Lu

Committee Member 3

Greg Waite

Abstract

Massive flank failure is a fairly common process in the evolution of volcanoes, having occurred at over 400 volcanoes worldwide. However, such events are infrequent relative to other volcanic phenomena, making observations and records of collapse events rare. Moreover, deformation measurements indicative of instability can be the complex result of both dynamic processes and the composition and morphology of the edifice. Hence, the processes and conditions that initiate, propagate, and arrest volcanic landslides are poorly understood. This work combines field studies, laboratory experiments, remote sensing, and numerical modeling to measure and interpret deformation events at the active Pacaya Volcano in Guatemala. Interferometric synthetic aperture radar (InSAR) measurements reveal that during eruptions in May of 2010, the west and southwest flank of the edifice experienced large, discrete landsliding that was ultimately aborted. The movement is distinctive in both the magnitude and spatial extent of the slide, being the largest slope displacement (~4 m) recorded at a volcano that did not result in a catastrophic debris avalanche such as the 1980 event at Mount St. Helens. 3-D displacements derived from pixel offset tracking techniques indicate that the majority of the cone, rebuilt from a previous flank collapse, moved downslope along a complex failure surface involving both rotational and along-slope movement. Notably, the lack of continuous movement of the sliding area in the years leading up to, and after the event emphasizes that active spreading should not always be expected at volcanoes for which triggering factors (e.g. magmatic intrusions and eruptions) could precipitate sudden major flank instability. Laboratory analysis of rock collected from Pacaya under volcano-specific events such as cyclical stressing, thermal stressing, and high temperature reveal different process-specific behaviors that could influence numerical hazard analyses of slope stability and deformation models. Understanding the nature and mechanics of this slope instability is critical for the estimated 35,000 people that may be affected in the event of a catastrophic flank collapse. Continued efforts such as those described in this dissertation can help to anticipate and mitigate what is arguably a collapsing volcano.

Recommended Citation

Schaefer, Lauren, "Nature and mechanics of slope instability at Pacaya Volcano", Campus Access Dissertation, Michigan Technological University, 2016.

https://doi.org/10.37099/mtu.dc.etdr/208