Fragments of once-living creatures inside volcanic rocks can help to trace an eruption to its source.

New Zealand's North Island is blanketed in debris from a super-eruption of the Taupo volcano at the island's centre, which happened some 25,000 years ago. A team led by Alexa Van Eaton at the Victoria University of Wellington searched for microfossils in rocks as far as 850 kilometres from the volcano. They found abundant skeletons of algae known as diatoms (pictured), including a type that lives only in lakes on the North Island. This confirms the findings of earlier work that the eruption blasted through a lake on that island.

Credit: ALEXA R. VAN EATON/ DAVID FLYNN

Such fossils could help volcanologists to work out the locations and environmental settings of past eruptions, the authors say. They speculate that volcanoes might even disperse living cells across long distances.

Geology http://doi.org/nr8 (2013)