2 February 2018
Landslides in the Maipo Valley, Chile
Last month I was in Chile working with colleagues from the Universidad de Chile and Universidad O’Higgins on our Newton-Picarte Fund project looking at seismically-triggered landslides in the vicinity of Santiago. We were lucky enough to spend a couple of days in the Maipo Valley in the Andes, which is home to the most extraordinary collection of very large landslides. The image below shows a Google Earth view of the area. As the image shows, this is a region of fascinating but complex geology, high relief and, of course, a variety of landslide types.
In the southwest corner of the image above a large landslide can be seen. This is a very active earthflow that is the result of mobilisation of an area of intensively hydrothermally-altered rocks. The upshot is a very spectacular, very active flow:-
However, most of the landslides in this valley are rockslope failures. As the image below shows this is a landscape that is dominated by landslide processes:-
In many areas the landslides are controlled by structural weaknesses in the bedrock. The area shown below is one of the best examples that I have ever seen. The massif in the background has a series of planar surfaces that mark previous rockslide events. Note the dispirate orientations and slope angles. This is a beautiful example of the ways in which local planes of weakness can dominate slope behaviour. These are hoever very large in scale ( hundreds of metres in length and width.
The image below shows two of these surfaces, which have generated a very large translational rockslide. Analysis suggests that it is likely that this rockslide was triggered by an earthquake:-
As a result there are numerous rockslide deposits in the valley, such as the one shown below, providing evidence of past catastrophic rock avalanches:-
In places the boulders that form the deposits are vast. This is one such deposit – note the people in the bottom left of the image for scale.
This project was funded by NERC via the Newton-Picarte Fund. Grant: NE/N000315/2: Seismically-induced landslides in Chile: New tools for hazard assessment and disaster prevention. I appreciate their help and support.