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WHERE DID THEY GO?


No one knows exactly what happened to the dinosaurs but there are several popular theories one of which is of an extinction level event such as pictured here.


Extinction Level Event:

In 1973, Walter Alvarez made a fascinating discovery. In the Cretaceous- Tertiary boundary of the rocks in the Umbrian Apennines of north central Italy he found a layer of reddish clay. Alvarez, who was there to study the earth's magnetic field, wasn't even thinking about dinosaurs but the ramificiations of this find would prove to be enormous.

Alvarez noticed that the clay beneath the reddish clay was full of fossils. Above the reddish clay, the stratum was nearly barren of fossils. What also was significant about this clay was that it was abnormally high in iridium; in fact 30 times higher than normal. It was then theorized that the large preponderance of iridium may have been caused by a huge asteroid impace on earth.

The asteroid, at least 10km in diameter, hurtling through the atmosphere at 100,000 km an hour, would have caused devastating effects upon impact. It would have left a crater 200 km wide and spewed a torrent of dust that would have enveloped the earth in darkness. Violent earthquakes and titanic tidal waves would have occurred. For several years the debris from the asteroid would have left the earth in a perpetual night-time. Without the sun, the plants would have died and the food chain would be severely disrupted thus ending the lives of many, many species on earth.

Another piece of evidence that supports the asteroid theory, is the discovery of an immense crater in the Yucatan Penninsula called "Chicxulub" This crater is approximately 180km across although it's original size may have been as large as 300km across. This crater appears to have been formed by an asteroid strike roughly the same time as the dinsosaurs vanished from the earth.



(Information on Chicxulub kindly supplied by The Tony and Ian Short Network. :))

A Gradual Decline into Extinction




This is the way Cretaceous life ended
This is the way Cretaceous life ended
This is the way Cretaceous life ended
Not abruptly, but extended.

Opponents of the asteroid impact theory, feel that evidence points to the fact that dinosaur species were already on the decline for many years before they eventually died out completely.

Gradual environmental changes could have been detrimental to most dinosaurs survival. Perhaps there was a shortage of vegetation due to these changing climatic conditions thus killing the herbivorous dinosaurs therefore also killing the carnivorous varieties.

Gradual extinction theorists put forward the following scenario: In the last few years of the cretaceous, the seas retreated from the land. Many shallow seas dried up. Everywhere, ocean levels were reduced by 100 to 200 meters. Mountains were being raised, volcanos were erupting and land was rising and spreading. Globally, the temperatures were cooler; dinosaurs sought more habitable climes but many were unable to due to the continental separations that had been occurring since the super landmass called Pangaea. Small animals adapted to their surroundings. Furred mammals flourished. Because of their long lifespans of 75-300 years, dinosaurs were unable to make fast-enough evolutionary adjustments to their new environments. Eventually, they perished. The reign of the "terrible lizards" was over.


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