WorldWide Drilling Resource

39 WorldWide Drilling Resource ® JUNE 2015 Geothermal Drilling Exposes Twin Scars Adapted from Information Provided by the Australian National University A geothermal drilling research proj- ect near the borders of South Australia, Queensland, and the Northern Territory has lead to the discovery of an impact zone nearly 250 miles wide caused by a huge meteorite that broke in two moments before it slammed into the earth. Although the crater from the impact, which occurred millions of years ago, has long disappeared, a team of geophysicists has found twin scars of the impacts hid- den deep in the earth’s crust. This is the largest impact zone ever found on earth. According to lead researcher, Dr. Andrew Glikson from the Australian National University (ANU) School of Archaeology and Anthropology, each of the two asteroids must have been over 6 miles across. “It would have been curtains for many life species on the planet at the time,” said Dr. Glikson, who is also affil- iated with the ANU Planetary Science Institute. The revelation of these ancient violent impacts may lead to new theories about the earth’s history. “Large impacts like these may have had a far more significant role in the earth’s evolution than previous- ly thought,” Dr. Glikson said. The exact date of the impacts remains unclear. The surrounding rocks are 300- 600 million years old, but evidence of the type left by other meteorite strikes is lacking. For example, a large meteorite strike 66 million years ago sent up a plume of ash which is found as a layer of sediment in rocks around the world. This event is suspected to have led to a mass extinc- tion event on the planet, including many dinosaur species. However, a similar layer has not been found in sediments around 300 million years old. The geothermal research project came upon clues to the impacts while drillingmore than 6500 feet into the earth’s crust. The project’s drill core contained traces of rocks that had been turned to glass by the extreme temperature and pressure caused by a major impact. Magnetic modeling of the deep crust in the area traced out bulges hidden deep in the earth, rich in iron and magne- sium, corresponding to the composition of the earth’s mantle. “There are two huge deep domes in the crust, formed by the earth’s crust re- bounding after the huge impacts, and bringing up rock from the mantle below,” Dr. Glikson said. The two impact zones extend through the earth’s crust, which is about 18 miles thick in this area. Editor’s Note: In between our print issues, the WWDR Team prepares an elec- tronic newsletter called E-News Flash . Based on readership, this was the most popular E-News Flash E-News F article of the month. Get in on the action and subscribe today at: www.worldwidedrillingresource.com " ; # 511-,(2 0) 20'5&43 %9 4+(3( ,/( $/5)$&452(23 ; 08 029'0/ # ! : : $8 $,- 3$-(3 *,6(/3,/4(2/$4,0/$- &0. "(% ,4( 777 *,6(/3,/4(2/$4,0/$- &0. Dr. Glikson with a sample of suevite - a rock with partially mel ted mater ial formed during an impact. Photo by D. Seymour courtesy of anu.edu.au