- How an asteroid impact causes extinction -
By Michael Paine for explorezone.com
"Imagine: NASA scientists announce they have detected a 10-mile-wide asteroid on a collision course with the Earth. They calculate it will hit Southeast Asia in two weeks. There is no chance of Bruce Willis being sent on a beefed-up Space Shuttle to blow up the asteroid. Earthlings will have to ride out the impact. The world economy grinds to a halt as people take to the hills. Anarchy sets in, civilisation breaks down. Accusations fly over the lack of warning -- where was Spaceguard, the proposed international search effort for large asteroids?
People in Brazil feel less vulnerable than most of the world's population. They are on the opposite side of the Earth from the predicted impact point. But one hour after the impact Brazilians notice some brilliant meteors. Then more meteors. Soon the sky gets brighter and hotter from the overwhelming number of meteors. Within a few minutes trees ignite from the fierce radiant heat. Millions of fragments of rock, ejected into space by the blast, are making a fiery return all over the planet.
Only people hiding underground survive the deadly fireworks display. Within three hours, however, massive shock waves from the impact travel through the Earth's crust and converge on Brazil at the same time. The ground shakes so violently that the ground fractures and molten rock spews from deep underground. Maybe Brazil wasn't the best place to be after all.
The survivors of the firestorms, tsunami and massive earthquakes emerge to a devastated landscape. Within a few days the Sun vanishes behind a dark thick cloud -- a combination of soot from the firestorms, dust thrown up by the impact and a toxic smog from chemical reactions. Photosynthesis in plants and algae ceases and temperatures plummet. A long, sunless Arctic winter seems mild compared to the new conditions on most of the planet.
After a year or so the dust settles and sunlight begins to filter through the clouds. The Earth's surface starts warming up. But the elevated carbon dioxide levels created by the fires (and, by chance, vaporisation of huge quantities of limestone at the impact site) results in a runway greenhouse effect. Those creatures that managed to survive the deep freeze now have to cope with being cooked.
Many species of plants and animals vanish. The few hundred thousand human survivors find themselves reverting to a Stone Age existence.
Is it fiction?..."
Mass Extinction Table: