ANU News (The Australian National University) (May 20, 2010)
"Scientists from The Australian National University have identified a dome at least 50 kilometres in diameter, buried under the Timor Sea that was created by a giant asteroid that collided with Earth around 35 million years ago - a period of heavy extraterrestrial bombardment.
"Their findings, which could suggest a link between these impacts and a sharp fall in global temperatures preceding the formation of the Antarctic ice sheet, have been published in the new issue of the Australian Journal of Earth Sciences...."
This news most likely won't have much of an effect on gasoline prices in South Africa, or the outcome of the next Massachusetts election, but I think it's interesting, anyway. Then again, look at this blog's label cloud: I'm interested in a mess of things.
Back to that 35,000,000-year-old undersea dome the Australian scientists found. It doesn't have anything to do with whatever killed off the dinosaurs - they'd been dead for roughly 30,000,000 years by the time something fell out of the sky and hit what's now the Timor Sea. And Siberia. And the western Atlantic.
Those three - at least - major impacts must have been a spectacular event. Which I don't mind missing: not one bit.
"...Dr Glikson said 'The minimum size of the Mount Ashmore dome, which represents elastic rebound doming of the Earth crust triggered by the impact, is 50 kilometres at the base, but the full size of the impact crater - not yet defined - may be significantly larger'.
" 'The identification of microstructural and chemical features in drill fragments taken from the Mount Ashmore drill hole revealed evidence of a significant impact,' Dr Glikson said.
"Dr Glikson said that the period when the asteroid hit coincided with a time of heavy asteroid bombardment of the Earth, which may have played a role in the sharp drop in global temperatures at the time.
" 'Round the same time as the Mount Ashmore impact, a 100 kilometre wide asteroid impact structure formed in Siberia, and another measuring 85 km in diameter in Chesapeake Bay, off Virginia, in the United States. Likewise a large field of tektites – molten rock fragments splashed by impact – fell over northeast America. This defined a major impact cluster across the planet,' he said.
" 'This impact cluster hit Earth about one million years before the Drake Passage, the ocean gap between Antarctica and South America, opened up. The opening of the Drake Passage allowed continuous circulation of the circum-Antarctic ocean current, isolating the Antarctic continent and allowing the onset of its large ice sheet, which acts as a "thermostat" for the Earth's climate.'..."
I've made the point before, that Earth has been a comparative quite place for the last few centuries - apart from little outbursts like what happened at Krakatoa / Krakatau in 1883 and - on a much smaller scale - Mount St. Helens in 1980. That graph, from the USGS, gives you an idea of how big the recent volcanic blowouts that we know of were. Then, there are events like that periodic eruption at the Yellowstone Caldera, and the whatever created the Deccan Traps.
That's what comes blasting out of the ground. There's trouble coming from the other direction, too. As the Australian scientists pointed out, big rocks fell out of the sky about 35,000,000 years ago.
It wasn't the first time - and probably won't be the last.
This planet is not always a particularly safe place to live.
But studying what's happened before gives us a better understanding of what to expect. Right now, there isn't much we can do about major volcanic eruptions: but it looks like we've got the technology to deal with incoming asteroids.
Provided that the folks with the know-how get the support they need, to save all our lives.
That's another topic.
- "Asteroids and Earth: Time for the Space Patrol?"
(May 2, 2010)
- "Dinosaurs, Runaway Volcanism, Change, and Evolution"
(March 24, 2010)
- "Looks Like a Big Rock Killed the Dinosaurs"
(March 7, 2010)
- "Asteroid 99942 Apophis: Radical Waves in 2036?"
(December 31, 2009)
- "Asteroid Impact? Yes; Dinosaur-Killing Firestorm? Maybe Not"
(December 31, 2009)
- "Frail, Delicate Little Mother Nature?!
(December 20, 2009)
- "Life Could Have Survived Earth's Late Heavy Bombardment"
(May 24, 2009)
- The Late Heavy Bombardment happened about 4,000,000,000 years back
- The one 35,000,000 years back, mentioned by the Australian University article, was much more recent
- "Asteroid Threat: Good News, We Have the Technology; Bad News -"
(April 28, 2009)
- "Astroid Patrol? Defenders of the Spaceways? This isn't Science Fiction"
(June 23, 2008)