Friday, January 14, 2011

The End of the Dinosaurs - Cretaceous and Paleogene periods

The End of the Dinosaurs

Dinosaurs reigned over the Earth until about 65 million years ago. All of a sudden they died out because of a drastic change in the conditions that made their life possible. The most reasonable hypothesis for this change attributes it to the collision of a large asteroid or comet with the Earth. The resulting fire devastated all of what today are the North and South American continents. The impact raised huge dust clouds that remained suspended in the air for months, darkening the planet. At the same time, sulfur, chlorine, and nitrogen was mixed into dense clouds, causing killing acid rains.

More Theories About the “K-T Boundary”

The period between the Cretaceous and Paleogene periods, known as the “K-T boundary,” marks the end of the era of the dinosaurs. Although the impact theory is widely accepted, other theories suggest that there was a great change in climate that caused dinosaurs to become extinct very slowly as the shallow seas withdrew from solid land. According to the defenders of these theories, the dinosaurs were being reduced in variety and number throughout a period that lasted millions of years. The large meteorite of Chicxulub, according to this hypothesis, would have fallen some 300 thousand years before the end of the Cretaceous Period. It has also been hypothesized that mammals proliferated before the extinction and fed on reptile eggs, or that the plants  eaten by the large sauropods succumbed to diseases.

Profound Evidence

In the Mexican town of Chicxulub, on the Yucat√°n Peninsula, there is a depression 62 miles (100 km) in  diameter that is attributed to the impact of a meteorite about 65 million years ago. The layers of rock that  make up the soil support this theory and make it possible to see what occurred before and after the impact.  

Volcanic Eruptions 

Another theory relates the massive extinction with the appearance of prolonged volcanic eruptions on Earth  that emitted asphyxiating gases and darkened the skies with dust. Thousands of cubic miles of volcanic rock  found on a plateau in DeccanIndia, support this theory. 

Space Cataclysm 

Every 67 million years, the Solar System crosses through the plane of the Milky Way. At those times some  stars in the Milky Way can cause comets to escape from the Oort cloud and enter the inner Solar System. It  is possible that one of these bodies could have impacted the Earth.  

 - Surya Chaitanya