A huge meteor which slammed into the southern Pacific Ocean about 2.5 million years ago generated tsunamis hundreds of meters high, and may have destablilized the entire planet's climate system.
Australian researchers say that because the Eltanin meteor - which was up to two kilometres across - crashed into deep water, it's not received as much attention as it should.
"This is the only known deep-ocean impact event on the planet and it's largely been forgotten because there's no obvious giant crater to investigate, as there would have been if it had hit a landmass," says Professor James Goff of UNSW's Australia-Pacific Tsunami Research Centre.
"But consider that we're talking about something the size of a small mountain crashing at very high speed into very deep ocean, between Chile and Antarctica. Unlike a land impact, where the energy of the collision is largely absorbed locally, this would have generated an incredible splash, with waves literally hundreds of metres high near the impact site."
Geologists and climatologists have interpreted geological deposits in Chile, Antarctica, Australia, and elsewhere as evidence of climatic change, marking the start of the Quaternary period. But it's possible that, instead, some or all of these deposits may be the result of inundation by a mega-tsunami almost unimaginable in scale.
"There's no doubt the world was already cooling through the mid and late Pliocene," says co-author Professor Mike Archer.
"What we're suggesting is that the Eltanin impact may have rammed this slow-moving change forward in an instant - hurtling the world into the cycle of glaciations that characterized the next 2.5 million years and triggered our own evolution as a species."