Chicxulub General Information
Size of the crater: 180-200 km
Age: 65 millions years
Site: Mexican Yucatan Peninsular; 21º24´N 89º31´W
Size of the body: 14-18 km in diameter
Velocity: 20 km/sec

Investigation History
The history of Chicxulub crater is not a long one. And it is closely connected with the history of paleontology.
As the study of dinosaurs has begun, many hypotheses for their extinction were promoted. One thing the scientist knew for sure – they couldn’t possibly have died out slowly, as many others prehistoric animals, for example mammoths, which became extinct due to human activity. The size of the creatures and their hunting ability made it impossible to develop for many other living creatures, especially mammals, which were killed vastly by the dinosaurs. So it was obvious that some kind of catastrophe was the reason. But what could have been the reason for a global ecological catastrophe?
With the continuation of paleontology studies the famous K-T boundary was found. It is the geological signature for the Cretaceous-Tertiary extinction, which occurred about 65.5 millions years ago ("K" is the traditional abbreviation for the Cretaceous Period, to avoid confusion with the Carboniferous Period, abbreviated as "C"). Since the label "Tertiary" is no longer recognized by most geologists as a geologic 'Period', the K-T demise might also be called the Cretaceous-Paleogene (or K-Pg) extinction event. The boundary is in fact a very clear border between two periods in the life of the Earth. It is marked as the border under which the dinasours fragments were numerous, and then, all of a sudden, a completely new forms of life could be found, altough it is clearly visible, that for some time the life on the Earth has almost stopped. The K-Pg extinction was certainly not the largest, it is only one of five known major extinctions. But it one of the most spoken about. The K-Pg border is visible everywhere in the Earth, but no logical theories existed to explain it’s origin. In 1980, a team of researchers led by Nobel-prize-winning physicist Luis Alvarez, his son geologist Walter Alvarez and chemists Frank Asaro and Helen Michels discovered that sedimentary layers found all over the world at the Cretaceous-Tertiary boundary contain a concentration of iridium hundreds of times greater than normal. Iridium is extremely rare in the earth's crust because it is very dense, and therefore most of it sank into the earth's core while the earth was still molten. The Alvarez team suggested that an asteroid struck the earth at the time of the K-T boundary. The fact that thae K-T border contains the isotopic of the iridium much closer to this of the meteorite than of the Earth and that any meteorite contais the amount of iridium close to the total amount of iridium in the Earth oly support the impact theory. Also a lot of shocked quartz granules, glass spherules and tektites are common, especially in the deposits around the Caribbean.
Though the theory seemed perfesly logic at that time, the debates around high velocity impact as a reason for mass extinction was severely debated among geophysists and paleontoligists for almost a decade. One of the reasons for the argument was that no crater of the proper size could be found on the Earth.
But a few years later the perfect crater was found on the coast of Mexico, near the town of Chicxulub on the Yucatan peninsula. Most of the blast debris would head toward the modern USA. The fact that the impact happened right at the coast would make tsunamis possible, the evidence of which can be found all over Mexico and Southern USA. Though for several decades the certainty about Chicxulub impact as the main cause of mass extinction was absolute, now it is once again a material for vast debates. Gerta Keller suggests that the Chicxulub impact occurred approximately 300,000 years before the K-T boundary. The theory is based on the fact that materials containing impact debris can be found almost 10 meters lower than the K-Pg boundary. This finding supports the theory that one or many impacts were contributary, but not causal, to the K-Pg boundary mass extinction. However, many scientists reject Keller's analysis, some arguing the 10 metre layer on top of the impact spherules should be attributed to tsunami activity resulting from impact. The Chicxulub crater remains in the centre of a very large controversy.

Reconstruction of the impact
After the estimation of the amount of iridium in the K-Pg border the size of the asteroid was estimated. It is considered to be between 7-14 km in diameter. The speed must have been approximately 20 km/sec, which makes its energy equal to 100 trillion tons of TNT, which is about 2 million times as great as the most poweful thermonuclear reaction.
An impact of this energy would have certainly created a large crater immediately, causing deformation in the Earth’s surface. A mixed cloud of dust, vaporized water and other substances, remains of the meteorite would rise from the Earth, reaching the height of several hundred kilometres above the surface. An incredible shockwave would spread both in the surface, causing strong earthquakes, and in the air, cutting trees, crushing objects. The air would be hot, wild fires would start all around.

Ecological effect
While it is still not certain that Chicxulub was the main reason for mass extinction, it surely have contributed a lot to it. So let’s discuss the possible consequences of the impact.
The most obvious consequence of such an impact would be a vast dust and aerosols cloud which would block the sunlight, stop photosynthesis for several years and thus brake an important food chain, with the result in gradual extinction of all the animals dependant on plants at first, and predators later. This theory has been proved as a large part of the cretaceous flora died out completely and many of its plants are unique to this period. As a result, many animals would be deprived of their only food and would not survive. In about fifty years the fauna of the Earth would change greatly.
But those vast changes almost wouldn’t affect any mammals. The food chain of prehistoric mammals was based on some small plants and organisms which did not require sunlight for sirvival. Also, most of those mammals were living in deep caves so the light didn’t reach them at all at any time, so those changes would not be huge for those creatures. Anothers reason is that most of the mammals are warm-blooded, while dinosaurs are cold-blooded. So any climatic changes would have affected them much more. Another important factor is that mammals mostly had some kind of fur, helping them to survive while cold periods. So “long winter” or even an “ice age” wouldn’t cause much harm. As a result, prehisotic mammals, our ancestors, did survive.
Another consequences of the impact besides the major climatic changes might include vast fires in the wooded areas, resulting in the death of many species of plants and animals. Huge tsunamic waves are also possible. They could have washed out flora and fauna of vast terrioiries.
To conclude all the information, I’d like to stress that no matter what the effects were, they all could lead to one very important fact – the extinction of dinosaurs and a huge impetus to the development of mammals. Just think of it – without the impact, our life would not have been possible!!!

Cultural effect
Studying any scientific event, it’s impossible to mention its effect on people’s minds, their culture, their life as a whole.
The Chixulub crater event is unique. It might be a reason for our existence, and, as a result, our culture at all. Nowadays it’s hard to imagine that our existence once depended on the smallest probability of an asteroid stricking the Earth at that very place at that very moment. The total history of 65 millions was changed completely.
It is also really important to mention that the discovery of Chixulub crater and investigation of its history gave many research material for scientists, provoking many other side researches, giving an impetus to many fields of science, including paleontology, geophysics, astronomy. Without all the debates around that subject, the development of impact cratering would have stopped a long time ago. Now, it is one of the most interesting fields in science, with millions of people attracted to the subject by its enigmatic appearance.
And probably the best known part of the subject is its effect on the science fiction. Let’s remember “Jurrassic Park”. Then just think about such a movie as “Armageddon” or “Meteorite”. They both depict a huge asteroid heading towards the Earth, and I both cases the impact can provide mass extinction and destruction of the whole civilization. The interest in the subject of mass extinction of dinosaurs and asteroid impacts was provoked mainly by the discovery of Chixulub.