Gigantic Markagunt and Sevier Gravity Slides Resulting from Mid-Cenozoic Catastrophic Mega-Scale Failure of the Marysvale Volcanic Field, Utah, USA

Robert F. Biek, Peter D. Rowley, David B. Hacker, Geological Society of America Staff

"The Markagunt and Sevier gravity slides are gigantic landslides that resulted from gravitationally induced catastrophic failure of the southern flank of the Oligocene to Miocene Marysvale volcanic field. Each is nearly 100 km long with runouts over the former land surface >35 km; together they span 7000 km2 and rank among Earth's largest terrestrial landslides. Basal cataclastic layers, injectites, pseudotachylyte, deformed clasts, and a variety of kinematic indicators demonstrate catastrophic emplacement, which was preceded by slow gravitational spreading of the volcanic field. This volume offers a history of their discovery, our current understanding of the gravity slides, and a guide to particularly instructive exposures for which the authors document their conclusions about the size, age, and significant structural features of these newly discovered features"--