Canada and the World
Current Events with a Canadian Perspective
Last update
23 February 2011
Dinosaur Extinction Theories
The accepted theory is that collision with an
asteroid caused the demise of the dinosaurs;
this idea is now being challenged
Creationist theory notwithstanding, dinosaurs roamed the planet for about 160 million years. They were present on every continent and completely dominated Earth’s environment. Then suddenly, 65 million years ago, most of them vanished. Why?
Climate Change Causes Extinction
Among paleontologists it is widely accepted that fairly sudden climate change was behind the mass extinction of life forms that took place about 65 million years ago.
The belief is that the climate change caused vegetation to die off, with catastrophic consequences for the large herbivorous dinosaurs. In turn, the carnivorous dinosaurs that preyed on the herbivores lost their source of food and died off as well.
What is not agreed upon so widely is what caused the climate change.
Asteroid Impact in Mexico
The asteroid impact theory is popular; this says that about 65 million years ago, a large asteroid slammed into Earth. The asteroid was about 10 kilometres in diameter and it slammed into what is now Mexico, at Chicxulub, on the Yucatan Peninsula as shown in this artist’s impression.
NASA: Donald E. Davis
The collision carved out a crater about 180 kilometres across and, says the University of California Museum of Paleontology its impact threw “up enough dust to cause the climatic change…the environment changed from a warm, mild one in the Mesozoic [period] to a cooler, more varied one in the Cenozoic.”
Crater in India Challenges Earlier Theory
Dr. Sankar Chatterjee of Texas Tech University has found a crater in India that is far bigger than the one in Mexico.
Reporting on the find, The Economist (October 2009) says Chatterjee’s crater “is 500 km across. The explosion that caused it may have been 100 times the size of the one that created Chicxulub. He calls it Shiva, after the Indian deity of destruction.”
He points to an underwater mountain off the coast of Mumbai (Bombay) as further evidence that some sort of apocalyptic event took place.
The peak of Bombay High stands about five kilometres above the seabed and it sits within the rim of the Shiva crater. Dr. Chatterjee suggests that this mountain was formed by magma that spewed out of a crack in the Earth’s crust. That fissure, he says, was caused by the massive impact of a large asteroid.
Dr. Chatterjee outlined his research on Shiva at the annual meeting of the Geological Society of America in Portland, Oregon, on October 18, 2009.
Volcanic Action Added to Climate Change
A press release from the Geological Society of America from two years earlier (October 2007) suggests another scenario: “A series of monumental volcanic eruptions in India may have killed the dinosaurs 65 million years ago, not a meteor impact in the Gulf of Mexico.”
Left behind by this volcanic action are the massive Deccan Traps beds of lava in
India. This geological feature is formed by multiple layers of basalt that cover
an area of 500,000 km2 (about the size of Spain) to a depth of more than 2,000 metres.
Princeton University paleontologist Gerta Keller has been studying the Deccan Traps and she has calculated that the volcanic eruptions that produced them “released ten times more climate altering gases into the atmosphere than the nearly concurrent Chicxulub meteor impact.”
Dinosaurs Hit by Three Calamities
These three events – the Chicxulub Asteroid, the Shiva Asteroid, and the Deccan Traps volcanic action – all occurred at about the same time in geological terms.
The dinosaurs and the other life forms that were wiped out with them could not survive such a devastating triple whammy.
Image credit
Douglas Hopkins
Sources
“What Killed the Dinosaurs.” University of California Museum of Paleontology.
“I am Become Death, Destroyer of Worlds.” The Economist, October 24, 2009.
“Dinosaur Death Outsourced to India.” Geological Society of America, October 27, 2007.
“Giant Impact near India -
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WHAT KILLED OFF
THE MIGHTY LIZARDS?
The folks at the Museum of Paleontology look at some of the alternative theories as to why the dinosaurs died out and shoot most of them down.
Hay fever. As flowering plants appeared dinosaurs had an allergic reaction to their pollen. The museum says there’s no evidence to support this theory and calls it “pretty silly.”
Crushed by size. Certainly some dinosaurs were huge and probably a bit lumbering, but they did not die because they were crushed by their own weight. Plenty of small, nimble dinosaurs became extinct as well as the big guys. And, so too did marine dinosaurs.
Competition from mammals. The museum faults the competition-
Death by cosmic ray. This idea is not as silly as it might seem but there’s no evidence of some catastrophe in space around the time of the extinction.
Dinosaurs simply faded away. Certainly, bird life in the world today evolved from dinosaurs, but most of the beasts disappeared over a very short time, geologically speaking. This hypothesis must go in the maybe column.
New dinosaurs are being discovered all the time. In February 2011 a team of scientists
announced the finding of Brontomerus mcintoshi in Utah. USA Today describes the animal
as “four-