The Azolla Event (https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event) was a cyclical bloom of duckweed-like ferns in the Arct

The Azolla Event (https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event) was a cyclical bloom of duckweed-like ferns in the Arctic Ocean about 49 million years ago which drew down atmospheric CO2 by an order of magnitude, from 3500 ppm (responsible for the warm, verdant climate you think about when you imagine the Mesozoic era) to 650 ppm (responsible for the cold, cyclical glaciations you think about when you imagine the modern world), and in which vicinity it has remained ever since.