21 November 2009

A very large ancient rockslide in Chile

Posted by Dave Petley

I am en route to Santiago in Chile to attend the Chilean Geological Congress, the organisers of which kindly invited me to give one of the keynote lectures (on Friday). I thought therefore that I would point out that Chile has an extraordinary set of very large rock avalanches. Earlier this year, Antinao and Gosse (2009) published an interesting review of a set in the Chilean Cordillera Principal. I do not intend to publish a full review of the paper here, but thought I would highlight just one of the slides, called Yeso – Meson Alto. This is a very large landslide, as the Google Earth image below shows:

I have eyeballed in the main landslide deposit (note that in places this is covered with more recent fluvial (river) deposits, so this is very approximate. I have used the supplementary information from Antinao and Gosse (2009) as a guide as this contains a map of the landslide, and another large slide downstream (which I have included below my indicative lines on the Google Earth image:

The statistics for this landslide provided by Antinao and Gosse (2009) are impressive:
Volume: 4.5 cubic kilometres
Original surface area: 22.7 square kilometres
Length (travel distance): 7.6 km

The landslide is considered to have been translational as the deposit retains the original stratigraphy. Interestingly, it is thought to have occurred in the Holocene (i.e. in the last 12,000 years).

Antinao, J., & Gosse, J. (2009). Large rockslides in the Southern Central Andes of Chile (32–34.5°S): Tectonic control and significance for Quaternary landscape evolution Geomorphology, 104 (3-4), 117-133 DOI: 10.1016/j.geomorph.2008.08.008