Each spring for 120,000 years, a thin layer of diatomite algae blooms appeared on the surface of Foulden Maar. Gradually filling in the 200m-deep lake, the layers of sediment preserved flowers, insects, fish and plant material that sank to the depths. What Foulden Maar would have looked like 23million years ago. After learning about other maars overseas, Prof Lee realised water birds like herons would have brought them in in their bills. New Zealand's fauna was "much, much more diverse" than it is today, Prof Lee said.

Source: Otago Daily Times May 24, 2019 16:32 UTC