Scientists caving for earthquake records

Scientists are exploring caves near Wairoa to develop a new method to date past earthquakes.

This new method if successful will be used alongside existing methods to date earthquakes and create a timeline of past earthquakes along the Hikurangi subduction zone.

Scientists use past earthquake records to figure out the future likelihood of earthquakes. Large Hikurangi subduction earthquakes are thought to happen very infrequently – around one every 800-1000 years.

“We will be looking for evidence of earthquake damage inside caves such as obvious physical damage like rock fall or cracked/broken stalagmites and stalactites as well as chemical changes inside stalagmites.” Say project leader Professor Joel Baker from the University of Auckland.

Stalagmites and stalactites are mineral deposits. As water drips from the ceiling of a cave, minerals are deposited and slowly build up over time. Stalagmites are formations on the grounds of caves whereas stalactites are the formation on the ceiling of caves.

Dating earthquakes using stalagmites and stalactites could prove to be more accurate than dating landforms such as raised beaches, sunken shorelines, offset river courses, fault scarps and landslide deposits that are used as evidence of past earthquakes.

“This new method could extend the existing earthquake record by tens or hundreds of thousands of years as cave deposits are relatively protected from surface erosion and stay preserved for much longer.” Says Professor Joel Baker from the University of Auckland.

This is part of a larger project on stalagmites and stalactites to investigate not only past earthquakes but also volcanic super-eruptions and the impacts of volcanism on local and global climate.

The three year project is led by the University of Auckland alongside Victoria University of Wellington, University of Waikato, GNS Science, University of Melbourne (Australia) and Centre for Star and Planet Formation (Copenhagen).

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