Sector collapse kinematics and tsunami implications

A collaboration between Prof. Sebastian Krastel (CAU, University of Kiel), Prof. Katrin Huhn (Marum, University of Bremen) and Prof. Christian Berndt (GEOMAR)

Funding by German Research Foundation (DFG)

Deep-seated collapses of volcanic islands have generated the largest volume mass flows worldwide. Understanding these mass flows is crucial because they are very hazardous as they might trigger mega-tsunamis. The way in which these collapse events are emplaced is poorly understood, even though this emplacement process determines the scale of associated tsunamis. Key questions such as whether they are emplaced in single or multiple events, how they may incorporate seafloor sediment to increase their volume, and how they are related to volcanic eruption cycles and migration of volcanic centers, still remain to be answered.

This project will form a crucial part of the first ever comprehensive study of large volcanic island landslide deposits and is directly linked to recent IODP drilling campaign in the Lesser Antilles (IODP Leg 340 in March-April 2012). Unfortunately, Leg 340 only recovered material from a single site (U1395) within the volcanic landslide deposits off Montserrat, and even at this site recovery was not continuous. This single IODP site is insufficient to document lateral variation in landslide character, which is critical for understanding how it was emplaced.

We therefore plan to take series of more widely spaced cores through this landslide deposit using the Bremer MeBo drill rig. We also want to collect a 3-D seismic data set that encompasses the two main volcanic landslide deposits offshore Montserrat. A pilot study had previously collected a smaller 3-D seismic cube, but only an unsuccessful IODP core site (U1393) is included in the cube.

Combining MeBo cores, IODP cores and 3D seismology will provide a unique dataset of the internal  structure, composition and source of material throughout a volcanic island landslide. The results will significantly contribute to understanding the emplacement of volcanic island landslides and they will allow us to assess the associated tsunami risk. With substantial geophysical background information and because IODP leg 340 has provided the only core material for volcanic debris avalanches in the world our results will provide profound new insights into the general mechanisms of sector collapse of volcanic ocean islands. These findings will be applicable to volcanic ocean island sector collapse in general and slope stability processes at island arc volcanoes in particular.

The project cruise is approved, but not scheduled jet.