23 December 2017

Villa Santa Lucia rock avalanche – images of the source zone

Posted by Dave Petley

Villa Santa Lucia rock avalanche – images of the source zone

Over the last few days images have become available of the source zone of the Villa Santa Lucia rock avalanche, which struck southern Chile last Saturday.  These include several images of the hillside prior to failure, most notably eight images tweeted by @OldClimber2 that provide views of the scarp area taken in April 2017.  This image shows the crown of the scarp, which displays large tension cracks and a fractured rock mass:-

Villa Santa Lucia rock avalanche

The crown of the source artea of the Villa Santa Lucia rock avalanche. Image via @OldClimber2 on Twitter.

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Whilst this image shows the deposit in the valley below, which was probably a mixture of colluvium and moraine (others will be able to judge this better than can I).

Villa Santa Lucia rock avalanche

The deposit below the scarp of the site of the Cilla Santa Lucia rock avalanche in Chile. Image via @OldClimber2 on Twitter

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Meanwhile, have tweeted images of the site after the landslide.  This image shows the landslide scarp:-

Villa Santa Lucia rock avalanche

The landslide scarp for the Villa Santa Lucia rock avalanche. Image via @Sub_Interior on Twitter

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Whilst this image shows the scarp and the start of the debris trail:-

 Villa Santa Lucia rock avalanche

The scarp and debris train from the Villa Santa Lucia rock avalanche. Image via @Sub_Interior on Twitter.

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Based on this it appears that the landslide consisted of a large volume rock slope failure that collapsed onto the colluvium and moraine at the based at the slope.  The images suggest that this the debris at least partially saturated (note the spring within the deposit nprior to failure) and it may also have contained substantial amounts of ice.  This deposit has mobilised to form a complex, high velocity rock avalanche / debris flow.  This image shows the track of the landslide:-

Villa Santa Lucia rock avalanche.

The debris trail from the Villa Santa Lucia rock avalanche. Image via @Sub_Interior on Twitter.

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The trail suggest a high energy flow.  It is a part of this landslide that struck the town of Villa Santa Lucia, with tragic consequences.