Brian is interested in geomorphology - geologic research tries to understand the origin of the landforms (mountains, rivers etc) on Earth. On his web page he says he is trying to answer two fundamental questions: 1) How do local processes interact to form landforms and landscapes? and 2) How can we, as researchers, appropriately model and constrain these processes to explore the long-term evolution of the earth’s surface?
On Friday Brian will be talking about how to use river incision to understand deformation. Let's break that down. River incision refers to a river eroding downward through its riverbed which may be made of sediment or bedrock.The river begins at a higher elevation and incises or cuts or erodes downward through the bed it flows over. The river may leave its floodplain behind at a higher elevation of it may be lowered at the same time. Deformation refers to changes in the shape or volume of a rock body. Stress/pressure is often applied to rock bodies by plate tectonics for example. Rock bodies may bend in a ductile fashion (forming anticlines or synclines) or in a brittle fashion (faults that fracture rock bodies).
Rail lines outside Christchurch, New Zealand deformed in a ductile fashion in response of the earthquake of September 3rd 2010 (photo by Ian McGregor).
As the rock body under a river deforms, the river bed responds by becoming steeper (the elevation change down the river bed increases) and the width of the river bed becomes narrower (less distance between either side of the river bank). Both responses cause the river to become more erosive and the river will incise or cut down through its river bed faster. If the age of the beginning of the incision/cutting down is known, then the geomorphologist can calculate how quickly the river is eroding its bedrock.
Brian will be talking about rivers that drain off the Tibetan plateau. He has calculated how fast the rivers are incising the landscape by dating the time when incision began. Brian has used known earthquakes events as well as optically stimulated luminescence (OSL) dating techniques to calculate when the river sediments last saw sunlight to date the beginning of incision. Using his results Brian has helped us further understand the tectonics that are actively shaping our planet.
You can read more about these techniques at 'Rivers crossing growing folds' or in the Yanites folder in resources on Ctools.