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вторник, 20 ноември 2012 г.

Dinosaurs

Entrance to the long history of life on Earth disappeared countless species. But perhaps the most popular and certainly the most intriguing of which is the disappearance of the dinosaurs. Over millions of years these huge animals are undisputed masters of the planet. Are distributed on all continents and nothing can undermine their superiority.

But about 65 million years comes a time when the kingdom of one of the most successful forms of life ever existed, is over. Why go there - it's a mystery remained strong despite a number of theories explain, appeared over the years.
Theories are based on scant evidence left from this period. By examining rock formations and fossils can be collected important information about what has happened in the past. From these studies, experts have found that at the time of the extinction of the dinosaurs on Earth takes great upheaval.
The study of the natural history of the planet allows scientists to put the dividing line between the age of dinosaurs and the subsequent age of mammals. This boundary between two different periods of life on Earth divides the old Mesozoic era (the time of the dinosaurs) from the next era Cenozoic period (the time of mammals in which we live, and we as human beings). Geologists call the first era "K" and the second - "T", and so the mass extinction of the dinosaurs became popular as the "KT Extinction." But this time not only the dinosaurs disappeared. Fact half of life on Earth stops its development.
Geologists have found that the huge disruptions that occur on the planet are climatic in nature. It seems that conditions change dramatically, and the Earth is no longer a planet relatively stable temperate as in a Mesozoic era. Instead, it becomes cooler and changing world we know today, and over time occurred several ice ages. The speed with which changes occur within the period is inexplicable mystery. What could be the reason?
Two theories try to explain what happened. According to one change has occurred gradually and causes are rooted in the activity of the Earth itself. Others argue that it is a powerful cataclysm occurred, such that the Earth was struck by a meteor. Both hypotheses are supported by considerable evidence.
Supporters of version gradual climate change believe that it may be caused by powerful volcanic eruptions over a long period of time. This probably created a "greenhouse" effect and dramatically changed the global climate. Reliability of this theory gives the fact that geologists are sure that there was a period of increased volcanic activity at the end of the Cretaceous.
But as there is strong evidence for the idea of ​​volcanic activity, so there is a very reasonable argument in favor of the concept of a meteor strike. Indeed, it is even possible to have both things happened. Researchers found iridium powder between those layers of rocks that match time back about 65 million years. This unusual substance is found in significant quantities and show that you have come from two places - either comes from outer space, the dust is trapped in the atmosphere as a result of a meteor impact, or its source is molten mantle of the Earth, which is relatively rich of iridium.
In addition to paying attention to the structure of the Earth, scientists study and its appearance in an attempt to understand what happened. But one of the biggest problems that face is that today the world looks completely different than the time before 65 million years. This makes it extremely difficult trying to find any evidence of volcanic eruptions or meteor crater. But in 1980 there is a discovery, which is believed to provide evidence that scientists seek.
It seems that much of the Gulf of Mexico is actually a large crater. Known as Chiksulub crater, it formed part of the outline of the Yucatan Peninsula. Rocky formations which contain large amounts of "hit" quartz, which is formed by the extremely strong vibrations at impact. Estimated that to form such a crater meteor must have been with a diameter of at least 100 km. Collision with similar proportions large enough to have a truly global impact.
If the Earth was struck by a meteorite, this triggered a massive volcanic eruptions with large amounts of ash and release harmful gases. The latter is acid rain, which has poisoned water supplies and destroying plant life. Particulates in the atmosphere has caused a cooling of the Earth since the passage of sunlight through the atmosphere has been difficult. These are the conditions for the onset of nuclear winter.
Given that dinosaurs were thought to be cold-blooded animals, the effect of global cooling would have been catastrophic. Many animals are numb because their metabolism was delayed due to extreme cold. Food stocks also declined, because the destruction of plant life at one end of the food chain predators affect the other end. Most probably probably starved to death.
Over time, the climate is slowly starting to recover. After the initial cooling, increasing numbers of greenhouse gases have led to gradual warming and eventually become even hotter than before. Most creatures can only live in certain temperature ranges, and those who managed to survive the cooling, perhaps then died from the subsequent warming.
Such extremes may indeed have a more subtle effect on small mammals as they warm blood is good protection against sudden changes. So some people say they seen to explain the death of the dinosaurs.
One theory is that the survival of mammals is not only due to the fact that they grow better than the dinosaurs and more easily adaptable to survive in a changing environment. In the end, it seems that few before they disappear forever dinosaurs reached a new peak of evolutionary development. For example, large predators like Tyrannosaurus rex making progress in its development shortly before his death. Under an assumption mammals ate all the eggs of dinosaurs and so reduced their numbers. But in any case, the proof of this hypothesis is extremely difficult.
Focusing on the eggs is interesting from another point of view. Before hatching, many of today's reptiles are very sensitive to changes in temperature and fluctuations in this respect influence of sex. Continued climate change could lead to a considerable imbalance between males and females, and this has had a disastrous effect on the reproductive capacity and survival rates.
Although dinosaurs are the most famous species, disappeared so suddenly, they certainly are not alone. To date, science has recorded five mass extinction, the dinosaurs certainly hold championship. For example, at the end of the Permian period (290-248 million years ago), more than 90% of life on Earth is wiped out. Why?
Some scholars suggest that the disappearances have an element of periodicity and also the theory of an asteroid impact could exist another space reasons. Perhaps a comet or space cloud of particles that come into contact with the Earth roughly every 25 million years. To date, this theory has yet to be demonstrated and it has fewer supporters of the other theories discussed.
The science that deals with the determination of the causes of mass extinction is important for us today. Human beings might have become the most powerful force that can influence the world and to a certain extent we can shape and control our environment. But the feeling of power can be deceptive and we must be prepared to expect the unexpected.
Dinosaurs were also the dominant species, yet their dominance was brought to a sudden end. We can not be sure whether this is due to a single event like meeting a meteor or the result of a slow process of volcanic and tectonic activity. It may be a combination of two factors or caused by something else entirely, such as epidemic.
An unexpected stroke of upheaval as a meteor could potentially destroy our planet and even our supposed strength we no less vulnerable than dinosaurs. This fear is reflected in a number of films where he shows how, despite all the scientific achievements of the planet is afflicted apocalyptic catastrophes. Only now speaks that such a dramatic global climate change may in fact be caused by humanity itself.
Perhaps as human beings to reflect on the fate of the dinosaurs and to bear in mind. Many believe that the rapid development of technology in the last century led to drastic changes in climate. The fact that dinosaurs were probably killed by something, should make us think.
It is believed that in today's climate changes leading to the extinction of many species, and this can easily be compared with each of the major mass extinctions in the past. This disturbing information has led many scientists to believe that it is not uncommon to find ourselves on the verge of extinction similar.
This can only give us a strong impetus to understand the reason for the extinction of the dinosaurs. With the unveiling of this mystery might have a good chance to prevent our own extinction.

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