The extinction of dinosaurs must have been related to a major event. Something enormous had to have happened in order to completely devastate these really massive animals. The natural event must have been gigantic to have impacts such as the continent’s splitting, the formation of ridge expansions, and the fact that land sunk into the sea or risen above water. What is the most interesting part is that any other organisms living at the same era as the dinosaurs vanished as well after the giant catastrophe. There are three different theories that explain the disappearance of dinosaurs; The Alvarez Asteroid Impact Theory, the Climate-Change Theory, and the Volcano-Greenhouse gas theory.
The impact theory discusses the fact that asteroids landed abruptly on earth which made a catastrophic impact on earth. Scientists Luis and Walter Alvarez were studying the K-T (Cretaceous-Tertiary) (Buckley, 1997) boundaries in east Mexico. In 1979, they found quite a lot of iridium in a thick layer of clay. Below this layer, there were loads of dinosaurs’ fossils. Above it, there were none. Iridium is very rare in the earth. The iridium they found was thirty times more than the usual iridium found in clay normally (BBC). The Alvarez asteroid impact theory basically states that a gigantic asteroid hit the earth and wiped out the dinosaurs. In a matter of fact, there was so much Iridium that the asteroid that hit the earth would have been about ten kilometres big. The impact would have have been equivalent to 10,000 Hiroshima bombs, and would have created so much dust that it would have blocked the sun rays and heat from reaching the earth and the vegetation. The whole food chain then would have got disrupted and everything died out. Scientists discussed that asteroids contain quite a lot of iridium in them (BBC). They argue that as the asteroids hit the earth, the blast was so intense that the iridium spread all across the world in different parts. It was Yan Smith who first discovered the traces of the impacts by finding tiny balls of rocks in the K-T boundary. He claimed that they were the kinds of rocks that were created by really hot effects. In other words, something so hot might have happened in order to leave traces like these tiny balls of rocks, called spherules. When the big asteroid hit the earth, so many rocks may have flown in vapour. And as they landed back onto the earth, they landed with extreme amounts of heat, which may have created huge fires in the whole earth. These fires therefore explain the level of soot that scientists have found in addition to the Iridium in the K-T boundary. It was also said by scientists that the asteroid impact had created the fall of acid rain which was so chemical that it poisoned all water bodies. Last but not least, signs of fern spores were found in the K-T boundary which is a sign that a big impact had occurred because it died out all plants in the earth (BBC).
However, for the theory to be true, they had to find clear evidence of a crater of more than 200 kilometres in diameter, which they found in Mexico in a little village called Chicxulub. Nevertheless, as they went through more investigation, they have noticed that there was a thick layer of sandstone between the soot and the Iridium layer (BBC). It was quite a peculiar aspect so some scientist stated that a catastrophic tsunami of about 1000 meters might have pushed all the sand in the surface which is why layers of sandstone were found in the crater. But many other scientists argued on the fact that this theory did not make sense. There had to be a reason to why there was sandstone there. Basically they figured out that the spherules found happened way before the Iridium (BBC). So they have come to the conclusion that there were two impacts that happened 300 thousand years apart, the second one being the most impacting and therefore driving the dinosaurs to extinction. This is one theory that could explain the extinction of dinosaurs. Another theory that makes sense as well is the Volcano-Greenhouse gas theory.
Historians and Scientists state that before the earth went through the K-T event, it used to be a very volcanic place. Volcanic eruption were extremely frequent and happened every now and then because of earth’s instability. The problem volcanic eruptions caused was that they released green house gases and carbon dioxide into the air which trapped the heat more and made it unbearable for the dinosaurs to live and the food chain to be disrupted as well (Buckley, 1997). Scientists have also found some microbes in lava (Buckley, 1997). There are wide chances the dinosaurs went through an epidemic which extinct them. An aspect controversial to the Alvarez Asteroid Impact theory is that the element Iridium can also be found in the earth core and mantle (Buckley, 1997). So there are chances the iridium Luis and Walter Alvarez found in the clay in the Cretaceous-Tertiary boundaries came from the volcanic eruptions of that time since magma comes from the core and goes through the mantle. Yet, there is one last theory that explains the dinosaurs’ extinction.
Last but not least, there is the climate change theory which basically states that the earth’s climate started to shift tremendously (Buckley, 1997). The summer times were extremely burning and the winter times were absolutely freezing. The earth would shift in its orbit therefore the climate changed drastically fast which gave less time for the dinosaurs and other living organisms to adapt to the weather. The food chain was then disrupted again since there were less living species with time going. Because climate changed too radically, dinosaurs could not stand the weather; they would have frozen as they were exothermic (Buckley, 1997). Also, as climate would change, the ice caps would enlarge which would therefore lower the water level in the earth. The dinosaurs would have died due to lack of water.
These three theories are not evidences of the true reason to dinosaurs’ extinction. Their extinction is still a big mystery to the world researchers. However, one can deduct by comparing and contrasting the three different theories that they are quite similar in a way. Although we might not know the real reason to dinosaurs’ extinction, we may deduct that there was a drastic climate change in the earth that made it unbearable for them to live. All scientists are sure of is that such a big phenomenon has occurred at that time that it created gigantic impacts on the climate which resulted in their disappearance. However the answer maybe as simpler as this: that with time the dinosaurs have gradually just come to an end. It is also said an event similar to the K-T event is very likely to happen again if one takes account of the global warming and environmental changes the earth is going through.
Works Cited
BBC, "Science & Nature TV and Radio follow up." BBC. BBC. 24 Mar 2009 <http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dino_prog_summary.shtml>.
Buckley, A.. "Dinosaur Extinction Page." Dinosaur Extinction Page. 1997. 24 Mar 2009 <http://web.ukonline.co.uk/a.buckley/dino.htm>.
Documentary by Horizon on Youtube Divided into 5 different parts : <http://www.youtube.com/watch?v=6FmoJo9c270&feature=related>.
Powerpoint given by Doctor Bolton in class about Dinosaurs