The Cerro Caquilluco–Cerrillos Negros rock avalanches in Peru

Giant rock avalanches are rare but fascinating events. The scale of the largest is hard to imagine.  To generate such landslides certain conditions need to be met, most notably high topography with steep gradients.

In a short paper published a few years, Crosta et al. (2015) described the giant Cerro Caquilluco–Cerrillos Negros rock avalanches in the southern part of Peru, located in the vicinity of -17.63, -70.19.  This is the site of the so-called Arica Bend, which has one of the largest relief contrasts on Earth – the location is close to the coast; offshore the subduction trench extends to 6000 m below sea level, whilst the mountain tops extend to 6,300 metres above sea level.  In this area, the research team have identified a number of giant rock avalanches, some of the largest mapped to date.

The figure below, from Crosta et al. (2015), shows the rock avalanches mapped in this area:-

The Cerro Caquilluco–Cerrillos Negros Giant Rock Avalanches, from Crosta et al. (2015).

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The largest of these rock avalanches, at Cerrillos Negros, has a linear distance from the crown of the landslide to the toe of the deposit of 41 km; the total distance traveled along the track is about 43 km.  This landslide is shown in the Google Earth image below – I have annotated the landslide scar and the lower part of the landslide deposit:-

The Cerrillos Negros Rock Avalanche, as seen on Google Earth

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As the image shows, identifying the middle part of the landslide is quite difficult as the landslide deposit has smoothed out the topography, but once you get your eye in it is identifiable in broad terms.  Crosta et al. (2015) have reconstructed the landscape prior to the landslide occurring; from this they estmate that the failure volume was in the order of 10 km³.

As the first diagram shows, this is only the largest of many giant landslides in this area.  These rock avalanches deserve more detailed investigation, but the scale and the landscape (plus of course the climate) make this a challenging task.

Reference

Crosta G.B., Paolo F., Elena V., Hermanns R.L. 2015. The Cerro Caquilluco–Cerrillos Negros Giant Rock Avalanches (Tacna, Peru). In: Lollino G. et al. (eds) Engineering Geology for Society and Territory – Volume 2. Springer, Cham