Bernard, P. BoudreauDalhousie University, Department of Oceanographyhttp://oceanography.dal.ca/person/Boudreau_Bernard_P.html |
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MOTIONS IN A VEILED WORLD: BUBBLES AND ANIMALS IN SEDIMENTS |
| The combination of personal observations and recorded evidence guarantees that almost everyone in our society knows what an air bubble looks like in water and can describe the rudiments of its rise. The same can be said in reference to a fish swimming in water. Scientists and engineers have build solid theories and models of such motions and can predict the behavior of bubbles and, to a lesser extent, fish.
Yet bubbles commonly occur in marine and lacustrine sediments, and one would be hard-pressed to find many who know what such a bubble looks like and what happens when they rise. Near surface sediments also contain abundant worms and other infauna, but few would say they know what happens when these creatures move in this medium. Sediments cover some 70% of this planet, and it seems the height of incongruity that we are ignorant of what happens over most of the earth’s surface. A major problem with observing sediments is the fact that they are opaque. To circumvent this limitation, we have employed two recent technologies to image and capture data about bubbles in sediments: CT-scanning and controlled bubble injection. We have also made use of mechanically similar, but transparent media (gelatin). Our research results show that bubbles form and rise by fracturing sediment and gelatin and that linear elastic fracture mechanics (LEFM) provides an excellent description of these dynamics. Working with gelatin microcosms we also show that many types of infauna move via a fracturing process, which also follows LEFM. This latter result goes a long way in explaining the curious morphologies of some benthic organisms. in collaboration with:
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Ort |
| 03.02.2009 15:00 Uhr Großer Hörsaal |
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