The relationship between short-term tectonics and mountain building in New Zealand

"The project aims to improve our understanding of how mountains are built by combining high resolution geodetic (InSAR, GPS) measurements of present-day deformation in the South Island of New Zealand with geological data collected from the exhumed roots of the Alpine Fault.

In collisional zones, mountains are made by the interaction of external tectonic driving forces, internal gravitational forces and surface processes (erosion). The response of the crust to these forces is governed by the rheology of the crust. In the continents, one key question is whether crustal strength lies only in the upper seismogenic layer (Jackson et al., 2008) or is instead found in both the crust and mantle (Burov, 2010). Another key question is the degree to which mountain chains are supported dynamically by flow in the mantle (Molnar and Houseman, 2013). This project will address these major questions by combining new observations from satellite geodesy (InSAR and GPS) with rheological constrained from lower-crustal rocks exhumed in the Southern Alps.

The South Island of New Zealand is being deformed rapidly by the oblique collision of two regions of continental crust. This has created the dramatic Southern Alps and the Alpine Fault mountain range. Importantly, in the context of this project, high levels of annual rainfall are leading to rapid erosion and exhumation of rocks that had been deformed in the lower crust. Measuring the present-day rates of vertical motion across the Southern Alps is key to unravelling how they are formed, but existing measurements from GPS are very sparse (Beavan et al., 2010). The recent launch of the Sentinel-1 constellation provides an exciting opportunity to map vertical motions over the entire South Island for the first time (Elliott et al., 2015). By combining these observations with geological constraints on the rheology of rocks exhumed from the lower crust (Gardner et al., 2016), the student will be uniquely placed to understand how this major mountain chain was formed, and in particular to assess the contribution of strength in the lower crust and dynamic uplift from flow in the mantle.
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http://www.nercdtp.leeds.ac.uk/projects/index.php?id=514