Ancient Cataclysm Rearranged Pacific Map, Study Says

Julian Ryall
for National Geographic News
October 24, 2007
A cataclysm 50 million years ago changed the face of the planet from the Hawaiian Islands to Antarctica, according to new research.

The collapse of an underwater mountain range in the Pacific Ocean turned Australia into a warm and sunny continent instead of a snowbound wasteland and created some of the islands that dot the South Pacific today.

"We have found that the destruction of an entire mid-ocean ridge, known as the Izanagi Ridge, initiated a chain reaction of geological events," said Joanne Whittaker, a doctoral student at the University of Sydney's School of Geosciences who led the research.

Using geophysical data gathered by scientists from Australia and Russia, the team confirmed that the ridge plunged underneath a plate of Earth's crust that stretches between the Korean Peninsula and Japan.

The Japanese landmass then acted as a vast plug in the crack between the plates, changing their movement and rearranging the geography of the Pacific, the team found.

This eventually led to the emergence of dozens of small volcanic islands that dot the southwest Pacific, including Tonga and the island chains that run north and east from Papua New Guinea (see map).

"The cause of [this] major change in the motion of the Pacific plate has long puzzled scientists," Whittaker said.

The team also deduced that the event changed the movement of the Australian continent, causing it to move due north at 2.75 inches (7 centimeters) a year.

"Australia would have been located much further south and would have had a climate more similar to Scandinavia or Alaska" were it not for this event, Whittaker said.

"Only the very northern parts of the continent would have been warm."

"Controversial" Theory

At the time of the event, Antarctica and Australia were part of the same southern landmass.

(See related photo: "'Polar Predator' Dino Tracks Found" [October 23, 2007].)

Using data collected by Australia's national geoscience agency and Russia's Okeangeologia Institute, however, the team found that Australia fit against Antarctica more than 310 miles (500 kilometers) further east than was previously believed.

This discovery led the scientists to identify the change in Australia's course of direction and the chain reaction that caused it.

Gaku Kimura, a professor of earth science at the University of Tokyo, said the work of the Sydney team was "interesting because it is really controversial."

The new theory suggests that the ancient event is what caused a previously unexplained bend in an underwater mountain range known as the Hawaii-Emperor range, he explained.

Scientists had been perplexed at the geological processes that had caused the unusual formation.

Secondly, he pointed out, the "classical" interpretation of the timeline for these events put them at around 43 million years ago, a date that has been revised to around 50 million years ago in the new research.

Whittaker believes the new model has far-reaching implications for understanding the creation of natural resources in waters around present-day Australia, as well as the chain of volcanoes known as the "Ring of Fire" that circles the Pacific.

"Natural resources form under specific conditions where the timing and amounts of heat and stress … are crucial," Whittaker said.

"This will help locate natural resources, especially on the southern margin of Australia.

"Understanding how the plates moved will also provide a better base for climate models, which in turn help our understanding of present-day climate," she added.

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