plunge the world into an ice age
...that the freshwater weed Azolla may have grown in the Arctic Ocean with enough vigour to plunge the world into an ice age?
...that the freshwater weed <i id="mwCBk"><a href="./Azolla" id="mwCBo" rel="mw:WikiLink" title="Azolla">Azolla</a></i>  may have grown in the <a href="./Arctic_Ocean" id="mwCBs" rel="mw:WikiLink" title="Arctic Ocean">Arctic Ocean</a> with enough vigour to <b id="mwCBw"><a href="./Azolla_event" id="mwCB0" rel="mw:WikiLink" title="Azolla event">plunge the world into an ice age</a></b>?