2 February 2018

Landslides in the Maipo Valley, Chile

Posted by Dave Petley

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


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:-

Maipo earthflow

A large earthflow in hydrothermally-altered rocks in Chile


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:-

Maipo valley

A landscape dominated by landslide processes in the Maipo Valley.


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.

Maipo rockfall

Multiple failure planes in bedrock massifs.


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:-

Maipo planar failure surfaces

Planar failure surfaces in the Maipo Valley, Chile.


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

Maipo rockslide deposits

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


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.

Maipo landslide deposit

Large rock slide deposits in the Maipo Valley.


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.