Rano Kau caldera and slide area as seen from space. Image courtesy i-cubed
In late August 2008 Pete Kelsey was shown a recent landslide that had occurred during heavy rains on the seaward side of the Rano Kau crater.
Rano Kau is a volcanic caldera that, over the millennia, has filled with fresh water and floating mats of reeds. For centuries this lake has served as a source of fresh water for the island.
Rano Kau slide area from the sea. It is roughly 150 meters from sea level to the top of the caldera. The line indicates the approximate water level of the lake on the other side.
The issue is that the caldera wall facing the sea will eventually collapse and the contents of the lake will drain into the sea. The recent landslide has caused concern throughout the island as it is now clear it is not a question of if this will happen but when. There are other sources of fresh water on Easter Island but Rano Kau is the largest and most important water source on the island. The majority of the island’s water related infrastructure focuses on this lake.
The lake and at the collapsing caldera wall at Rano Kau.
The 3D model of the island created by the Autodesk team in 2007 can be used as a base map by which the level of erosion can be monitored. The challenges are very real however. It is extremely hazardous, if not impossible, to survey the caldera’s slopes. Furthermore the seas are consistently too rough to provide a stable platform for a boat mounted laser scanner. The only real solution will be to acquire satellite imagery taken every few months. The images could then be overlaid and compared to monitor change in the slide area.
Autodesk would like to thank La Armada de Chile for tour of the slide area and i-cubed for the satellite imagery.
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