About a decade ago, Luis Alvarez (a Nobel prize-winner) and his son Walter (a geologist) explained to the world why the dinosaurs became extinct. They claimed that a 10 km wide asteroid thundered into the earth 66 million years ago. This shocked the world.

Many delegates supported Walter and Alvarez at a seminar of ‘Global Catastrophes’. This seminar was organized jointly by the Lunar and Planetary Institute and the U.S. National Academy of Sciences. Many scientists said that the impact of the asteroids caused volcanic eruptions. These, in turn, flooded the earth with poison-spreading ‘substances’. There is evidence of this asteroid theory on the crust of the earth. Asteroids contain much of the chemical ‘iridium’. It is also found on the earth’s crust. So Alvarez concluded that the asteroid poisoned the earth. This killed the dinosaurs too.

However, nobody has found iridium deposits matching with other big extinctions. Moreover, they have not found any crater to support this asteroid theory. Therefore, some have brought out other theories also. These are of volcanic eruptions, vast forest fires, and acid rain.

Some scientists are of the opinion that there had occurred volcanic eruptions. They would have released dust and gas in plenty changing the climate considerably. There could have destroyed many forms of life. Volcanoes discharge sulphurous gases which are poisonous. These might have added to the destructive nature of such eruptions.


There is the evidence of a global forest fire in the soot. It was deposited in layers at and after the end of the dinosaur era. It is believed that the carbon dioxide formed by soot and oxygen would have raised global temperatures. This would been raised through the ‘green house effect’ or the trapping of solar radiation. Such a fire may have produced toxins. However some scientists don’t believe in it. They maintain that many species of animals and plants survived this fire.

Under the acidic rainfall theory, it is believed that acidic rain fell over a period of years. It destroyed the natural vegetation that the dinosaurs ate. Without it, they starved themselves to death. However, there is no evidence of this theory.

The disappearance of the dinosaurs is still mystery. However, the scientific research in this direction is still going on.