The above diagram is the scientific speculation of the Alvarezes. Luis Alvarez said also that ‘the pollution in the atmosphere would settle on the ground all over the Earth, creating the layer of iridium that he and his son discovered in Italy.’
What are the facts that support this theory?
Luis Alvarez and Walter Alvarez found the layer of iridium, that they later based their Asteroid Impact Theory on, in Italy but layers like this have been found all over the world.
The reason why the layer was first noticed to be unusual was because of the vast quantities it was discovered in. Iridium is a very rare element and for it to be found in such large amounts there must have been a momentous and significant event in which this huge amount of iridium was unearthed. Alvarez then researched as to where this iridium could have come from. The main place where iridium is known to exist is in outer space, another place is in the core of the Earth. The only part of the Earths crust where measurable amounts of iridium can be found is in volcanic areas. The Alvarezes decided that the most likely theory from the evidence they had collected was that an Asteroid hit the Earth sending up the dust from the Earths surfaced where the asteroid had landed but also any debris from outer space that was on the asteroid, for example iridium. An asteroid between 4 and 9 miles long would have had enough impact on the Earth and carry enough iridium to explain the mass extinction and the layer of iridium in Italy.
Another fact that backs up the theory of Luis and Walter Alvarez is that special ‘shocked quartz’ that was found in the layer of iridium. Shocked Quartz is quartz crystals that are physically changed when exposed to extreme heat and pressure. This would definitely ‘fit in’ with the Asteroid collision theory put forward by the Alvarezes. Here is a picture of a sample of ‘Shocked Quartz.’ The many parallel lines illustrates what happens to quartz when it is put under high pressure and exposed to high temperature; a environment that would be created by an asteroid hitting the Earth.
But what does this tell us about the effect of the impact on the Earth?
(j) A 6 mile diameter (almost 10km) asteroid would have the velocity of over 6300mph (100,000km/h). This is a great example of data from a website. At this huge velocity the asteroid would have demolished everything within almost 500km radius of the actual of the point of impact. A definite result of this would have been huge fires and a colossal shock wave that would have traveled long, long distances. The actual object would have vaporized on impact and this would have sent trillions of tons of dust, gases and water vapor into the atmosphere. Numerous massive tidal waves would have caused even more damage, killing more dinosaurs all over the world, far away from the asteroids point of impact. High winds, earthquakes and a huge increase in volcanic activity would have also followed the collision, killing millions more dinosaurs. The high winds would have spread the debris, thrown into the air by the asteroid impact, all around the world; forming a cloud that would have blocked out sunlight for months. This would have decreased the temperature of the Earth dramatically. After this, global fires would release considerable amounts of CO2, resulting in the temperature of the Earth increasing. (e)This CO2 would later cause chemical reactions that would have created acid rain that covered the entire Earth.
The effects on the land dinosaurs would have been catastrophic! Dinosaurs required a lot of food and sunlight to live, both of which would have been lost by a big asteroid hitting the Earth. Research carried out on soot known to be of the dinosaur extinction period showed scientists that around 25% of all vegetation on Earth would have been completely destroyed, not by the asteroid but by the global fired that occurred after the collision. As stated previously the herbivore dinosaurs would have died first, creating a knock-on effect that would have resulted in a mass extinction.
The effects of the asteroid collision would have been just as deadly and powerful in the sea as on land. Oxygen levels in the sea would plummet causing the death of plankton, the basis of any marine food chain. The lack of plankton would have resulted in the starvation of all marine reptiles because it crumbled the food chain. The death rate amongst the shelled sea animals like the ammonites would have dramatically decreased too as an effect of the asteroid hitting the Earth and the acid rain could have acidified the seas, causing even more deaths among sea species.
What are the facts that challenge this theory?
There are two major problems with the Asteroid Impact theory. Firstly, (f) dinosaurs died out gradually. If an asteroid hit the Earth all dinosaurs would have died out very quickly and not over a long period of time. This would suggest that the cause of the mass dinosaur extinction would have had gradual, long lasting effects.
The next problem with the asteroid theory is that (f) there had been previous, proven asteroid impacts that had not caused mass extinction. What could have been so different about this collision that it killed creatures that had lived on the Earth for over 150million years?
Mini Conclusion
The Asteroid impact theory is very plausible and has a lot of scientific evidence to back it up. The layer of iridium proves that the Earth was in a truly volatile state 65 million years ago and that there was a sudden change in the Earths environment that caused a great change in the natural living conditions for all animals and dinosaurs. The factual evidence about how shocked quartz is formed again proves that the Earths environment was very unstable and dangerous. However I am concerned that other asteroids had hit the Earth previously and no mass extinctions occurred then, what made this collision so deadly?
VOLCANIC THEORY
What is the background information of this theory?
Some scientists disagree with the Asteroid Impact theory; claiming that a set of consecutive volcanic eruptions could have been the cause of the mass extinction 65million years ago. The Deccan Traps Volcanism-Greenhouse Dinosaur Extinction Theory was compiled by Dewey McLean in (b) 1979. He stated in his scientific paper that as an effect of the many active (b) volcanoes in India 65 million years ago all erupting consecutively, CO2 was released into the atmosphere.
Dewey McLeans scientific paper would have had to gone through the process of peer review. This is where scientists who are experts in that particular field critically evaluate a scientific paper. This process is carried out mainly before but also after the publication of a scientific paper.
The world was in a very unbalanced period 65 million years ago, especially when considering the carbon cycle. Apart from the famous Deccan Trap eruptions, other volcanic parts of the world had become unsafely active. Examples of this would be the Cameroon volcanic line in Western Africa and other pre-existing hotspots. McLean says that the Earth was overwhelmed by natural CO2 emissions and was environmentally altered due the greenhouse effect.
What are the facts that support this theory?
What was India doing 65 million years ago that caused the repeated volcanic eruptions?
In the late Cretaceous period (just before the dinosaurs became extinct) (b) India was an island like piece of land that was drifting away from Africa, towards Asia. It was suggested by McLean that whilst India drifted over a mantle plume (Figure 2) causing many volcanic eruptions on the land. Molten rock rises out of the core of the Earth, through the mantle plume, bursting out of a volcano as a huge eruption of lava that often covers vast amounts of land.
Dewey McLean’s has said that ‘the vast bulk of the Deccan Traps lavas erupted onto earth's surface’ causing the mass extinction of dinosaurs. From this I decided to research exactly what the Deccan Traps were on an online encyclopedia. Here is what I found out. (d) The Deccan Traps are a large igneous province located on the of west-central India and one of the largest features on Earth. They consist of multiple layers of solidified that together are more than 2,000 m thick and cover an area of 500,000 km². This means that Deccan Traps are large areas of land on Earth which have lots of magmatic rock present. A common example of magmatic rocks is basalt. Deccon Traps were created between 60 and 67 million years ago by numerous volcanoes erupting in India at around the same time. Here is an image (Figure 2) that shows us where the Deccan Traps were at the time of the continual eruptions and where the magmatic rocks are still covering modern day India. (i) Even after 65 million years of erosion the Deccan Traps in India are one-half miles thick!
It has been suggested by McLeans report that the volcano responsible for the formation of the Deccan Traps is the Piton de la Fournaise present on the Reunion Island (Indian Ocean). Piton de la Fournaise is one of the most active volcanoes on the Earth, even today. It most recently erupted on the 21st September 2008. The Piton de la Fournaise is still releasing the chemical iridium. The layer of iridium was also used to prove the Asteroid Impact theory but McLean has put forward in his report that he thinks that the iridium layer is due to the volcano eruption. Using Figure 2 we can see that iridium from the core of the Earth can reach the surface of the Earth through a mantle plume. This could definitely explain the layer of iridium between the Late Cretaceous and Early Tertiary period.
The consecutive Deccan Trap eruptions in India would have overwhelmed the Earth with a huge amount of CO2 that ultimately would have killed many animals because it caused the carbon cycle to become greatly unbalanced. McLean says that the great amount of CO2 in the atmosphere would have ‘triggered greenhouse warming, chemical changes in the oceans and the K-T mass extinctions.’
So what would the effect of the extra CO2 in the atmosphere be on the animals of 65 million years ago?
Firstly, eggs and young embryos would have certainly overheated and died due to the sudden global warming. Also a large increase in the temperature of the Earth would have damaged the male reproductive system, making it impossible for some species to reproduce. With lack of offspring the populations of some species would have diminished. This would have altered the food chain causing animals and dinosaurs to find different sources of food. If larger animals were not affected themselves from the temperature increase their prey would have been; resulting in decreasing numbers of larger creatures due to a lack of food. Over hunting and huge population failure would have lead to a mass extinction.
What are the facts that challenge this theory?
There have been many other floods of basalts due to volcano eruptions all over the world. For example there was major volcanic activity in Greenland approximately 55 – 61 million years ago. It is known that this eruption caused at least 10 million cubic kilometers of magma. This would have had similar effects to that which McLean says caused the mass extinction 65 million years ago. (g) However there was no mass extinction 55 million years ago, many scientists argue that this proves that McLean must be wrong.
Mini Conclusion
The Volcanic Eruption Theory is again a very plausible theory that uses factual evidence to prove its point. The evidence put forward proves that the Earth would have been plunged into a volatile state. Though it is obvious that the volcanic eruptions would have caused many species around the eruptions to become extinct it is still debatable whether this deadly environmental condition would have been present globally. Therefore it is questionable if a chain of consecutive volcanic eruptions would have cause a mass extinction.
CONCLUSION
Make a conclusion
I believe that there is very strong and plausible evidence for both the Asteroid Impact theory, put forward by Luis Alvarez and Walter Alvarez, and the Volcanic – Greenhouse Effect Theory, put forward by Dewey McLean. I have looked carefully at the evidence for both of the theories and come to the conclusion that they both caused a mass extinction 65 million years ago. I think that the only way that a mass extinction could have been caused 65 million years ago is if both events happened in a relatively short amount of time.
Describe the facts that support this conclusion
I think that both of the incidents occurred consecutively because of the vast amounts of very conceivable evidence that has been presented for each argument. Firstly, in the clay layer that separates the Late Cretaceous from the Early Tertiary period there are lots of elements that would be found in both environments; where an asteroid has hit the Earth and where a huge chain of volcanic eruptions have occurred. If an Asteroid had hit the Earth (blocking out sunlight) it would have definitely caused the death of many species but it is debatable whether a single collision would have caused a mass extinction. However if an asteroid hit the Earth and it caused a massive chain of volcanic eruptions the effects would have been much more serious. The animals and dinosaurs that had survived the initial impact would have been very weak and it is very possible that major volcanic activity would have caused a mass extinction. This explains many of the doubts of the two theories. For example a doubt for both theories is that there had been various asteroid collisions and volcanic eruptions previously on Earth that had not caused mass extinctions; however, never had a massive asteroid hit the Earth and a chain of consecutive volcanic eruptions occurred so closely together.
WHAT DOES THIS COURSEWORK SHOW ME?
Explain what ideas about science I have gathered from carrying out this coursework
This coursework has caused me to learn a lot more about scientific ideas. Firstly it has shown me that even though scientists may be shown the same data and evidence they can sometimes come to very different conclusions. This tells me that creating theories has a lot to do with a scientist’s imagination and creativeness, not just the facts and figures that they are able to uncover. It can also show me that we may never know exactly what happened to cause a mass extinction 65 million years ago, all we can do is predict.
BIBLIOGRAPHY
A list of websites and books that I used and what exactly they showed me
About dinosaurs – page 3
‘What were dinosaurs?’
(a)
I initially dismissed this website as an unreliable source because it seemed to look quite childish and unprofessional. I soon reolised, after research some of the interesting facts presented on this website, that it is actually very factual and was simply produced with an audience of a young generation in mind. This website turned out to be very useful, giving me a good understanding of what exactly dinosaurs were.
About volcanoes – pages 6, 7 and 8 volcanic theory
(b)
This was a very reliable source. It was the actual scientific report published by Dewey McLean. This scientific report had been though the process of peer review, making it very reliable because it had been accepted by some of the top scientists in the dinosaur extinction field as a plausible and well-evaluated theory. Though I could not find the peer review it was definitely carried out.
Asteroid impact – pages 4, 5 and 6 Asteroid Impact Theory
(c)
This was again a very reliable source as it was from a website called PBS, a recognized, informative organization.
Deccan traps info
(d)
This is possibly one of the lesser reliable sources. Wikipedia is well known for its ability to give information about any chosen subject, however it is also very famous for the lack of reliability in this information. Wikipedia answers are up loaded by any one who feels that they know a little about the subject. These people would be little or no science. I therefore had to be very careful when looking at information from this site.
asteroid impact theory – pages 4, 5 and 6 Asteroid Impact Theory
(e)
Twenty First Century GCSE Core Science Higher Textbook (page 42)
Evidence against the Asteroid Impact Theory – page 6
(f)
The Twenty First Century Textbook is a very reliable source. It is produced by the well-known exam board ‘Twenty First Century Science’ and is recognized around the world. Something that possibly makes the information I received from this Textbook more suited for my Case Study is that it is aimed at people my age. Therefore any information I used would be at a scientific level that I should be able to understand.
Twenty First Century GCSE Core Science Higher Textbook (page 43)
Evidence against the Volcanic Eruption Theory – page 8
(g)
The Twenty First Century Textbook is a very reliable source. It is produced by the well-known exam board ‘Twenty First Century Science’ and is recognized around the world. Something that possibly makes the information I received from this Textbook more suited for my Case Study is that it is aimed at people my age. Therefore any information I used would be at a scientific level that I should be able to understand.
Walking With Dinosaurs – Tim Haines (page 280)
Asteroid Impact Theory Evidence
(h)
Tim Haines is an award winning scientific journalist who has worked with the BBC since 1988. This makes him and his work recognized globally as being up to date, very factual and reliable.
Walking With Dinosaurs – Tim Haines (page 281)
Volcanic Eruption Theory Evidence
(i)
Tim Haines is an award winning scientific journalist who has worked with the BBC since 1988. This makes him and his work recognized globally as being up to date, very factual and reliable.
Asteroid Impact Theory
(j)
I expected this to be an unreliable source. It was not a link from a recognized organization but rather just a non-recognized enthusiast. However it is obvious from the vast quantity and detail in the report that the writer knows a lot about this field and has a lot of information to offer.
