Canyon erosion - analogy with subaerial fluvial and colluvial systemsThe graphs on the right compare the relationship between channel gradient and rainfall catchment area for mountain rivers in Taiwan (based on data published by K Whipple) with similar graphs calculated for the continental slope canyons, deriving catchment area in the same way as with river drainage basins. Surprisingly the two sets of data can show a comparable relationship (graph slope) between gradient and area. The submarine data however tend to show a greater diversity of forms. In these examples (from the Virginia slope), the graphs tend to curve below A<10^7 m^2. This project aims to resolve the origin of this relationship, drawing analogies with erosion of river systems. For further information see these pages on modelling submarine canyon development by erosion. |
Rates of submarine erosionRates of erosion (exhumation) are difficult to ascertain because the material representing the erosion history is usually absent or difficult to relate to the erosional terrain. There are tools in subaerial geomorphology to address this issue, such as cosmogenic radionuclide dating of exposed surfaces, fission-track and He dating, other dating of strath surfaces and terraces, and sediment budgets. In the submarine landscapes, these tools are mostly not available or at least difficult to apply. This project made a first attempt using submarine slopes of volcanoes in the Canary islands, where the different ages of the volcanoes provide a chronology. We found that the greater depth of incision around Tenerife compared with El Hierro (a younger volcanic island) was compatible with the slow denudation rates seen in subaerial lowland landscapes. Rates are larger than found in the deep sea but smaller than subaerial tectonically active landscapes. For further information see: abstract and full article (PDF)*.The figure on the right shows the morphology of northeast Tenerife (Anaga) and western El Hierro derived from multibeam sonar data. The technique explained in the article quantifies the difference in ruggedness of the submarine slopes, the older slope of Tenerife showing many gullies and canyons. |
See also:
Accumulation of sediment deposits around mid-ocean ridges,
which includes geomorphological modelling (diffusion) of sediment surfaces and quantifying the spatial
distribution of deposition,
Quantifying rock slope geomorphology of mid-ocean
ridge escarpments based on observations made from submersible dives. This work examined
the gradients of different lithologies and found a significantly smaller maximum gradient
for serpentinite, which may relate to serpentinite's unusual bulk rock properties.
The study also looked at the geometries of talus fans and
speculated on their relation to tectonic history.
Relevant publications
Funding for this work was provided by a Research Fellowship
from the Royal Society. The data around the Canary Islands was collected
with NERC funding to DG Masson and AB Watts.
Collaborators and advisors on aspects of this work have included Brian Dade (Dartmouth, NH),
Doug Masson (SOC, Southampton, UK), John Huthnance (Proudman Oceanographic Lab, Liverpool) and
Lucy Ramsay and Niels Hovius (Cambridge).
*The American Geophysical Union owns the copyright to this document. Further reproduction or electronic distribution of them is not permitted.
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