Studies of submarine slope failures in the North Atlantic: Causes, timing and consequences

Submarine landslides are a significant geohazard to offshore infrastructure and coastal areas. They occur worldwide on the slopes of volcanic islands and continental margins. In the NE Atlantic, many large-scale Holocene and Pleistocene submarine landslides are located at the mouth of cross-shelf troughs and were probably triggered by earthquakes. Discussions on critical preconditioning processes for slope failure relate to cyclic sedimentation patterns during glacial periods, gas hydrate dissociation caused by changing pressure and temperature condition, and over-steepening due to toe erosion or uneven sedimentation patterns. However, the significant geological destabilizing processes leading to slope failure are still not fully understood and require further studies. The main objective of this thesis is to gain new insights about the initiation of submarine landslides and to identify which particular destabilizing preconditioning processes make slopes prone to failure. This aim is addressed by the reconstruction of the failure chronology of the newly discovered Fram Slide Complex, and by a numerical modeling approach that investigates a new preconditioning process related to gas hydrates. (...

An 1888 Volcanic Collapse Becomes a Benchmark for Tsunami Models

When volcanic mountains slide into the sea, they trigger tsunamis. How big are these waves, and how far away can they do damage? Ritter Island provides some answers

Core-log-seismic integration in metamorphic rocks and its implication for the regional geology: A case study for the ICDP drilling project COSC-1, Sweden

Continental collision causes deformation in the crust along shear zones. However, the physical and chemical conditions at which these zones operate and the deformation processes that enable up to hundreds of km of tectonic transport are still unclear because of the depth at which they occur and the challenges in imaging them. Ancient exhumed collision zones allow us to investigate these processes much better, for example at the COSC‐1 borehole in the central Scandinavian Caledonides. This study combines data from the COSC‐1 borehole with different seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. This is one of the few studies that shows that core‐log‐seismic integration in metamorphic rocks allows to identify the spatial distribution of major lithological units. Especially gamma ray logs in combination with density data are powerful tools to distinguish between mafic and felsic lithologies in log‐core correlation. Our results indicate that reflections along the borehole are primarily caused by compositional rather than textural changes. Reflections in the Seve Nappe Complex are not as distinct as in greater depths but continuous and several of them can be linked to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. Our results suggest that ductile‐deformed middle crustal reflectivity is primarily a function of pre‐orogenic lithological variations which has to be considered when deciphering mountain building processes

Arctic megaslide at presumed rest

Published version. Source at http://doi.org/10.1038/srep38529. License CC BY 4.0.Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates