An island off the coast of Chile lurched upward during earthquakes in 1835 and 2010, but subsided in between. Such events provide a rare look at how Earth's crustal plates respond throughout an entire earthquake cycle.

Just after the 1835 quake, Robert FitzRoy of the HMS Beagle noted that seaweed and mussels had lifted as much as 3 metres above the shoreline of Santa María island. Now, a team led by Robert Wesson of the US Geological Survey in Denver, Colorado, has collected data from other old surveys and modern satellite measurements of the same island.

The scientists found that the island's height above sea level dropped by about 1.4 metres between 1835 and 2010, before rising 1.8 metres during the later quake. This suggests that strain builds up erratically where the Nazca and South American tectonic plates collide, indicating that the seismic activity in that region is more complicated than scientists had thought.

Nature Geosci. http://dx.doi.org/10.1038/ngeo2468 (2015)