Submarine Canyons: Applying Geomorphometry to understand their Evolution (CAGE)

(funded by a Marie Curie Intra-European Fellowship 2010-2012; Contract number: PIEF-GA-2009-252702)

Submarine canyons are deep, steep-sided valleys incised in the seafloor. They are major geomorphological features that dissect most of the world's ocean margins. Submarine canyons serve as temporary sinks and conduits for sediment, nutrients, organic carbon and associated pollutants, and they host a large quantity and diversity of habitats and biological communities. In spite of their relevance and widespread distribution, submarine canyons are still poorly known environments, and their formation is still subject to considerable debate. Most research has focused on basic mapping of canyon systems, and recent studies have mainly comprised qualitative descriptions of canyon morphology.

CAGE will entail a geomorphometric analysis of bathymetric data from submarine canyons in the Catalan and Patagonian margins that will improve our understanding of the geological processes responsible for canyon formation. This approach will allow us to characterise the large- and small-scale morphology of canyon systems in unprecedented detail, and to systematically investigate the link between morphology and individual sedimentary processes. The results will also be integrated with side-scan sonar imagery, seismic reflection data, and geotechnical and sedimentological data from sediment cores to isolate the fundamental processes responsible for canyon initiation and development, understand the nature and role of these processes, and reconstruct the evolution of canyon morphology.

Further information about CAGE can be found on:

Tubau, X., Lastras, G., Canals, M., Veres, O., Amblas, D., Rayo, X., Micallef, A. and HERMESIONE shipboard party (2011) Geomorphology of the Foix submarine canyon system, NW Mediterranean Sea, European Geosciences Union Annual Meeting 2011, Vienna, Austria.

Role of mass movements in canyon evolution

The Cook Strait sector of the Hikurangi subduction margin, off south-east central New Zealand, is dominated by a multi-branched canyon system where landslides are wide-spread. The objective of this study was to determine the character, origin, and influence of these landslides on the evolution of the canyon system. Multibeam bathymetry covering seven submarine canyons is utilised to characterise landslides’ spatial distribution, morphological attributes and area-frequency characteristics.  We demonstrate that mass movements within the Cook Strait canyons consist of spatially dense, predominantly retrogressive, small, deep-seated, translational bedrock landslides occurring in Late Cenozoic sequences. These landslides affect up to a quarter of the canyoned area. Concentration of landslides in the shallow canyon reaches (down to 800 m) is attributed to the influence of oceanographic processes originating on the continental shelf such as tide-generated currents, dense shelf water cascading and internal waves. Canyon incision and wall undercutting, locally favoured by underlying lithological control, are proposed as major landslide drivers in Cook Strait. Ground motion during regional earthquakes is considered a secondary cause. Retrogressive landslides are responsible for canyon widening and wall retreat, cross-sectional asymmetry, preconditioning for additional failure, destabilisation of adjacent slopes and delivery of sediment into canyon floors.

Micallef, A., Mountjoy, J.J., Canals, M. and Lastras, G. (2011) Deep-seated bedrock landslides and submarine canyon evolution in an active tectonic margin: Cook Strait, New Zealand, Advances in Natural and Technological Hazards Research.

Canyon morphology and evolution in active margins

PhD project carried out by Emma Cassar, funded by STEPS and co-supervised with Dr Joshu Mountjoy (NIWA) and Dr Godwin Debono (University of Malta)