The abundance of cosmogenic He-3 depends on the altitude of the surface and thus can be used to understand the altitude history of a rock surface. ![]() To investigate the timing of Andean uplift, Dr Laura Evenstar from Bristol’s School of Earth Sciences used a new method based on cosmic rays that create a rare form of helium (cosmogenic He-3) in minerals at the Earth’s surface. The timing of such uplift is important in helping scientists to understand how mountains form, how they erode and what impact this may have on global atmospheric circulation patterns and climate. When this large portion of dense material was removed, the remaining portion of the crust underwent rapid uplift. The prevailing view is that the Andes became a mountain range between ten to six million years ago when a huge volume of rock dropped off the base of the Earth’s crust in response to over-thickening of the crust in this region. However, the timing of when the Andean mountain chain uplift occurred has been a topic of some controversy over the past ten years. To get such a high mountain chain in a subduction zone setting is unusual which adds to the importance of trying to figure out when and how it happened. ![]() The Andes were formed by tectonic activity whereby earth is uplifted as one plate (oceanic crust) subducts under another plate (continental crust).
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