Dinosaur Extinction: "The Smoking Gun?"

ABC News is carrying a story about research performed by over forty different scientists that provides the strongest evidence yet that the reign of the dinosaurs came to an unceremonious end around 65 mya due to the impact of an asteroid the size of the Isle of Wight. Stuart Gary writes:

In this latest study, researchers examined the sedimentary material around the impact site and found it was far too violently churned up to provide a reliable dating record.

They found that farther away from the impact site, the sedimentary material becomes a single layer at the K-T boundary, matching the composition of rocks at Chicxulub.

They also determined that despite evidence for relatively active volcanism in India, ecosystems showed only minor changes within the 500,000 years before the K-T boundary event.

Only at the boundary do things suddenly change.

As the article notes, however, other scientists are not so convinced. One of my friends from graduate school said at the time that dinosaurs show steep decline ahead of the K-T boundary and that they hang around for awhile after the boundary, suggesting that other factors were at work. This is echoed by Steven Salisbury of the University of Queensland, who is quoted in the article.

----------------
Now playing: Derek & The Dominos - Layla
via FoxyTunes

Of Asteroid Impacts, Oxygen and Early Life Models

Sid Perkins of Science News writes that The Sudbury Meteor impact may have had a much more marked effect on our planet than first thought. He writes:

About 1.85 billion years ago, Earth’s now separate landmasses were joined in a single supercontinent. That also means there was one large ocean, says Cannon. Many scientists suggest that the object that slammed into Earth then — probably an asteroid abut 10 kilometers across — splashed down in that ocean, in waters about 1 kilometer deep on the shallow shelf surrounding the supercontinent. Models hint that the tsunami spawned by the event would have been 1 kilometer tall at the impact site and remained at least 100 meters tall about 3,000 kilometers away, Cannon adds.

Those immense waves and large underwater landslides triggered by the impact stirred the ocean, bringing oxygenated waters from the surface down to the ocean floor, the researchers propose.

Its all pretty hypothetical stuff and needs to be examined much more carefully to see if the model holds up to further observations. As Mr. Spock would say "All we have is a theory which happens to fit the facts." Still, it is more than we had.

----------------
Now playing: Oystein Sevâg - Children's Song
via FoxyTunes