Two recent items are worth noting:
Ultra-low oxygen could have triggered mass extinctions, spurred bird breathing system
Recent evidence suggests that oxygen levels were suppressed worldwide 175 million to 275 million years ago and fell to precipitously low levels compared with today's atmosphere, low enough to make breathing the air at sea level feel like respiration at high altitude.
Now, a University of Washington paleontologist theorizes that low oxygen and repeated short but substantial temperature increases because of greenhouse warming sparked two major mass-extinction events, one of which eradicated 90 percent of all species on Earth.
In addition, Peter Ward, a UW professor of biology and Earth and space sciences, believes the conditions spurred the development of an unusual breathing system in some dinosaurs, a group called Saurischian dinosaurs that includes the gigantic brontosaurus. Rather than having a diaphragm to force air in and out of lungs, the Saurischians had lungs attached to a series of thin-walled air sacs that appear to have functioned something like bellows to move air through the body.
Ward, working with UW biologist Raymond Huey and UW radiologist Kevin Conley, believes that breathing system, still found in today's birds, made the Saurischian dinosaurs better equipped than mammals to survive the harsh conditions in which oxygen content of air at the Earth's surface was only about half of today's 21 percent.
"The literature always said that the reason birds had sacs was so they could breathe when they fly. But I don't know of any brontosaurus that could fly," Ward said. "However, when we considered that birds fly at altitudes where oxygen is significantly lower, we finally put it all together with the fact that the oxygen level at the surface was only 10 percent to 11 percent at the time the dinosaurs evolved.
"That's the same as trying to breathe at 14,000 feet. If you've ever been at 14,000 feet, you know it's not easy to breathe," he said.
Ward believes low oxygen and greenhouse conditions caused by high levels of methane from intense volcanic activity are likely culprits in mass extinctions that occurred about 250 million years ago, at the boundary between the Permian and Triassic periods, and about 200 million years ago, at the boundary between the Triassic and Jurassic periods. He will make a presentation on the topic Tuesday at the American Geological Society annual meeting in Seattle.
and:
Japanese shipwreck adds to evidence of great Cascadia earthquake in 1700
Evidence has mounted for nearly 20 years that a great earthquake ripped the seafloor off the Washington coast in 1700, long before there were any written records in the region. Now, a newly authenticated record of a fatal shipwreck in Japan has added an intriguing clue.
Written records collected from villages along a 500-mile stretch of the main Japanese island of Honshu show the coast was hit by a series of waves, collectively called a tsunami, on Jan. 28, 1700. Because no Japanese earthquake warned of the waves, it is likely they came from somewhere else around the Pacific Rim, said Brian Atwater, an affiliate professor of Earth and space sciences at the University of Washington and a U.S. Geological Survey geologist.
In the village of Kuwagasaki (now part of the town of Miyako) 300 miles northeast of Tokyo, the tsunami is believed to have crested at about 10 feet, destroying 13 houses and starting a fire that consumed additional houses. Records from five other towns lend more evidence for a tsunami generated by a magnitude 9 earthquake off the Washington coast on Jan. 26, 1700.
Posted by DaveH at November 4, 2003 11:09 AM