What Really Killed the Dinosaurs?

[rodsky]

Two reminders of what may have caused the disappearance of dinosaurs just passed by the earth today, but they are puny ones.

-RODION

[analog man]

diseases somehow cause drastic fall of their specie family

[cromagnon]

Two reminders of what may have caused the disappearance of dinosaurs just passed by the earth today, but they are puny ones.

-RODION

u mean meteors passed by...

[cromagnon]

EXTINCTION OF THE DINOSAURS

(picture by NASA). At the end of the Cretaceous, 65 million years ago, not only did the dinosaurs disappear completely, but so did flying reptiles (pterosaurs), and marine reptiles (ichthyosaurs and plesiosaurs). In fact, between 60 and 80% of all animal species, including many marine forms, disappeared. Most turtles, crocodiles and primitive birds also disappeared but some survived to give rise to modern forms.
There have been numerous theories to account for the extinction of dinosaurs. But during the 1980's strong evidence was obtained to support the idea, originally proposed by Luis Alvarez, that a global catastrophe, caused by the impact of an asteroid, comet or meteorite, was responsible. Enormous amounts of debris would have been thrown into the atmosphere, making the Earth so cold and dark that cold-blooded animals like dinosaurs were unable to survive.
Supporting the impact theory, about 150 Impact Craters have now been discovered on the earth. One of the most spectacular is the Barringer Crater in the Arizona desert. (picture by NASA). The Barringer crater was formed about 30,000 years ago (much too young to have anything to do with dinosaur extinction). It is 7/10 mile across and 560 feet deep, and is thought to have been caused by an iron meteorite 200 feet in diameter, weighing one million tons, that hit the earth at a speed of 30,000 mph and released an amount of energy equivalent to the most powerful nuclear devices yet made. But it is tiny compared to some older craters.
The impact responsible for the extinction of the dinosaurs would have produced a crater at least 100 miles across. The entire planet shows a 3 mm-thick layer of rock at the appropriate level (i.e. exactly at the boundary between Cretaceous and Tertiary), containing several kinds of evidence for the impact:

a high concentration of the element iridium, which is rare in terrestrial rocks but common in meteorites

"shocked" quartz grains showing parallel, colored markings which are an indicator of violent impact

unusual amino acids, thought to be extraterrestrial in origin
In North America the 3 mm layer is underlain by a similar layer 2 cm thick, and it is thickest (46 cm) at sites near to Haiti and Cuba, suggesting an impact site in the Caribbean Sea. This layer contains many glass-like beads, mm to cm in diameter, that were probably formed by melting of rocks during the impact. The molten rock would have been ejected, and then would have fallen back to earth. The composition of these layers suggests an ocean impact.

[jangska]

like the crocodile and komodo dragon , living dinosaurs left..

Birds are the direct descendants of meat-eating dinosaurs in most scientists' opinions. Living reptiles like crocodiles are relatives of dinosaurs, but they came from animals that developed before dinosaurs, so they are just cousins of dinosaurs. Dinosaurs aren't birds or reptiles. They're dinosaurs, a separate, special group. Some living animals, like reptiles, look a lot like what we imagine dinosaurs to be, but that's just a coincidence. Reptiles all have bent legs, and dinosaurs have straighter legs. Dinosaurs walked with their legs underneath them — that's one way to tell a dinosaur is a dinosaur.

[cromagnon]

nice ... dinosuar first , flying animals... archeopteryx

[PeeJ]

pagchoor daniel oi! hahahah...

[analog man]

mosquitoes. malaria.

[geetarista]

next: humans...

[Count of Monte Cristo]

sulti sa akong science teacher, it was an asteroid that crashed to earth that killed the dinosaurs.