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.

Google Earth image of the upper part of the Maipo Valley

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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:-

A large earthflow in hydrothermally-altered rocks in Chile

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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:-

A landscape dominated by landslide processes in the Maipo Valley.

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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.

Multiple failure planes in bedrock massifs.

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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:-

Planar failure surfaces in the Maipo Valley, Chile.

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As a result there are numerous rockslide deposits in the valley, such as the one shown below, providing evidence of past catastrophic rock avalanches:-

Large rockslide deposits in the Maipo Valley – note the cars for scale.

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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.

Large rock slide deposits in the Maipo Valley.

Acknowledgement

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.