An­cient as­ter­oid clues in Pil­bara rocks

Pilbara News - - News - Chris Marr

An as­ter­oid four times the size of Rot­tnest Is­land plough­ing into Earth and goug­ing a crater the size of Vic­to­ria — it is the stuff of night­mares and it hap­pened 3.46 bil­lion years ago, ac­cord­ing to find­ings from the Pil­bara.

“The im­pact would have trig­gered earth­quakes or­ders of mag­ni­tude greater than ter­res­trial earth­quakes, it would have caused huge tsunamis and would have made cliffs crum­ble,” ac­cord­ing to Dr An­drew Glik­son, of Geo­science Aus­tralia.

This sce­nario comes about af­ter tiny spherules, or glass beads, formed from va­por­ised rock dur­ing the im­pact were found in a core sam­ple re­trieved near Mar­ble Bar.

The lo­ca­tion of the as­ter­oid im­pact is un­known.

“Mar­ble Bar is one of the very few ar­eas of the world where sed­i­men­tary rocks of this great age are pre­served, and where the rocks are so pre­cisely dated,” says Dr Arthur Hick­man, of the Ge­o­log­i­cal Sur­vey of WA.

This im­pact is the sec­ond old­est so far dis­cov­ered. “The old­est recorded im­pact oc­curred about 10 mil­lion years be­fore and is re­vealed by sim­i­lar, though much smaller, im­pact spherules found at North Pole, 50km west of Mar­ble Bar, and in South Africa,” Dr Hick­man said. Orig­i­nally pub­lished on Sci­ence Net­work WA, an in­de­pen­dent web­site based at Scitech. Read more at sci­encewa.net.au.

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