Who is the best known and disseminated two hypotheses that describe the cause of the extinction of dinosaurs.
One theory blames the disappearance of reptiles in a grand cataclysm that occurred 65 million ago. It could be an asteroid, a giant meteorite, possibly part of a huge comet. In any case, it is about the collision of Earth with a sort of space object. Another hypothesis sees the cause of extinction of dinosaurs in the earth itself, in its geological (volcanic) activity, changing the climate, the configuration of the land, the atmosphere.
None of the hypotheses have not yet received conclusive evidence.
Scientists again began to doubt the theory of dinosaur extinction, which states that the reason for it was the fall of an asteroid to Earth.It is believed that the extinction of the dinosaurs about 65 million years ago (and it's not vyzyvaaet doubt) was due to fall to Earth a huge asteroid. But scientists at the University of Washington suggest that prior to the collision of a celestial body and the Earth event occurred, doomed to extinction of the giant reptiles. Volcanic eruptions have destroyed much of the ocean of life, the bulk — snails and clams.
For much of the late Cretaceous period the conditions on Earth were fairly stable. Tens of millions of years, ran no different significant changes. Animal life on Earth may have become too "spetsializirovannnoy" too accustomed to stable conditions and a slight change of environmental conditions, such as fever or cooling of the atmosphere, could have detrimental effect on the population of the living world of dinosaurs in particular. Climate change could lead to the impoverishment of the vegetation, depriving familiar dinosaurs and sufficient power supply.
Dr. Thomas Tobin says that the eruption began at 300 — 200 thousand years before the alleged encounter with the asteroid and continued, apparently, for 100 thousand years. The ambience was thrown a huge amount of carbon dioxide and other gases as the greenhouse effect. This led to a warming climate, and the first phase of extinctions.
Volcanic activity, together with climate change, has led to the extinction of life on the ocean floor, deep in the water column. A fall of an asteroid destroying many species on the land surface and the upper ocean.
Study of the period of deposits held on the island of Seymour, geological layers that are rich in fossil deposits. Experts studied the material collected by magnetostratigraphy, determining the time of their formation. Dr. Tobin says that there is evidence of two different events, including warming.
There is currently no evidence of a connection of the two extinctions. But the first extinction, of course, influenced by the second. Ecosystem already been weakened by the eruptions and their consequences, and the blow of the celestial body has only aggravated the situation and led to a second Masov extinction.
Another part of the scientists agree extraterrestrial source version of extinction of dinosaurs and many other species. In the seventies of the twentieth century, information has been received, it is strongly influenced by the debate on the causes of death of the dinosaurs. It was found that the end of the Cretaceous and early Tertiary periods corresponds to the appearance of rock rich in iridium. Iridium — a very rare element in the Earth's surface, but its presence is very characteristic of meteorites.
Data on iridium in sediments gave a new impetus to the hypothesis of a collision with a celestial body at that time. Put forward an updated theory that at the end of the Cretaceous period (65 million years BC), a massive celestial body collided with the Earth, causing an explosion of enormous power, emissions to air, millions of tons of dust, shock wave of extraordinary power and fire.
Dust caused by a meteorite, eclipsed sun, gas fire increased greenhouse gas concentrations in the atmosphere, enhancing the greenhouse effect. Earth has undergone such an impact on the diametrically opposite field. India and the Yucatan Peninsula (now Mexico) 65 million years ago, located directly opposite each other. The powerful impact of a meteorite in one place could cause a manifestation of volcanic activity in the other. Or meteorite could split into two parts, of which one half fell to India, and the other part — the Yucatan. In any event, catastrophe theory is very popular.
Gaps and issues.
But there are nuances that are: statistical analysis study findings show that the extinction of the dinosaurs began millions of years before the end of the Cretaceous period. Most likely, they were on their way to extinction when the last stroke of the space cut their existence. Whatever the real reason, but the kingdom of the dinosaurs ended and the site was free for her studies of other species.
Volcanic eruptions manifest themselves throughout the epoch of dinosaurs. For example, a well-known Triassic deposits of ash. But the power of this volcanic activity could not be compared with what happened in the late Cretaceous period. I must say that the Chicxulub crater, located on the Yucatan Peninsula, formed by dropping a huge meteorite. Study of this issue is sure to bring a lot of interesting knowledge about the period of the Earth.