Why does Australia’s highest mountain exert such a gravitational pull?
Mar 15, 2016 | News | by The Learning Press staff
Scientists have scaled new heights to discover how Australia’s highest mountain was formed.
Mount Kosciuszko in the NSW Snowy Mountains stands out from other great mountains of the world because it wasn’t formed by a collision between continents.
It exerts a gravitational pull on the national psyche, with thousands of visitors flocking to Thredbo each year to brave the chairlift ride and the 13km hike to its summit.
Now geologists from the University of Sydney and the California Institute of Technology have discovered what caused the Snowies to reach their peaks - and it turns out that gravity has a starring role.
Using high performance computing code, the team discovered the range has an unusually strong gravity field.
Professor Dietmar Müller from the USYD’s School of Geosciences explained: “The gravity field led us to suspect the region might be pushed up from below so we started looking at the underlying mantle: the layer of rock between the Earth’s core and its crust.”
The team found the mantle under Australia’s east coast has been uplifted twice - the first time during the early cretaceous period when we were part of Gondwanaland.
During that period, the mantle was being stirred by old, cold tectonic plate sections sinking below other plates and into the deep mantle through a process called subduction.
“Eastern Australia was drifting over a subducted plate graveyard, giving it a sinking feeling,” said co-author Dr Kara Matthews.
“But around 100 million years ago subduction came to a halt, resulting in the entire region being uplifted, forming the Eastern Highlands.”
Fast forward through the next 50 million years and things start to get exciting again.
“Australia’s separation from Antarctica accelerated and it started moving north-northeast, gradually taking it closer to a vast mantle upwelling called the South Pacific Superswell,” co-author Dr Nicolas Flament said.
“This provided a second upward push to the Eastern Highlands as they gradually rode over the edge of the superswell.”
Professor Müller said the two-phase uplift theory is supported by geological features from rivers in the Snowy Mountains, where river incision occurred in two distinct phases.
“The model we built explains why the iconic Australian Alps exist and is also a new mechanism for figuring out how some other mountainous regions elsewhere in the world were formed.”
The team’s findings have been published in Earth and Planetary Sciences.
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