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Controversies in Science/What killed the dinosaurs

Points ForEdit

Scientists Settle DisputeEdit

Catastrophes of the AsteroidEdit

The Asteroid itself was not the sole cause of what killed the dinosaurs, but rather what occurred due to the asteroids impact. Not only did the asteroid's impact have enough force to cause serious damage, but the tsunami that followed also contributed to the death of wildlife in the immediate area. Thereafter, due to the amount of dust that lingered into the atmosphere as a cause of the impact, sunlight was blocked. This caused acid rains which further destroyed the earth. After this, with plant-life being damaged, herbivores began to die out, which in turn caused the death of the carnivores. With no leftovers to feast on carrions also began to die out from starvation. Finally, with no sunlight ecosystems were unable to produce oxygen and a cold "climate change" began to occur, explaining the possibility of an "ice age" [1].

In other words, yes perhaps climate change was the eventual cause of the dinosaurs death, however the events of the climate changes only occurred because they were triggered by the main event of the asteroid that impacted the Earth 65 million years ago [2].

Proof in the ClayEdit

The earth was impacted by a large asteroid that would send 60 times the asteroid's mass into the atmosphere in the form of dust. The dust would spread over the earth for several years, causing Cretaceous-Tertiary extinction. When they found the increase in iridium in rocks in several parts of the world compared to the background rocks it was dated back and concluded the increase was caused by the meteorite effect and that killed the dinosaurs.[3].

Was an asteroid responsible for the extinction of the dinosaurs?Edit

An asteroid struck the earth sixty-five million years ago which caused the dinosaurs to disappear. When the asteroid hit the earth, it raised a massive cloud of dust that covered the earth and blocked out the sun. This cloud was composed of Iridium[4].

Aftermath of the Asteroid that killed the dinosaursEdit

The asteroids impact created so much dust into the atmosphere that it plunged the earth into darkness and cold which in turn slowly killed approximately 90% of the wildlife. [5]. The force of the asteroid hitting the earth was 100 megatons of force which is equivalent to a billion times more explosive than the bombs dropped on Hiroshima and Nagasaki. [6] According to the fossil record dinosaurs were found to have died relatively swift according to the geographical span and based on the differences in th jews Org: National Geographic. (n.d.). Retrieved October 4, 2012, from National Geographic Website: http://www.geosociety.org/gsatoday/archive/15/3/pdf/i1052-5173-15-3-4.pdf</ref>.

Quick ExtinctionEdit

The dinosaurs were killed off in a relatively short time period, which appears to have been triggered by the period of global warming and devastation caused by a meteorite [7].

Post-impact Asteroid ConditionsEdit

The Cretaceous-Tertiary mass extinction is due to the post-impact ozone conditions from the asteroid collision in the Yucatan Peninsula in northeastern Mexico (The Chicxulub crater. [8].

Most Species of Archaic Birds that Existed in the Cretaceous do not Appear in the Paleogene EraEdit

The authors identify a total of 17 species that were present within 300,000 years of the Cretaceous - Paleogene era border. Fossil evidence claims those 17 species were not present in the Paleogene era [9]. Dinosaurs became extinct after the Cretaceous period. Paleontologists have been studying fossil and rock formations for further evidence [10].

The meteor that killed the dinosaursEdit

As studies have shown, approximately 65 millions years ago a meteorite struck the earth causing a large dust cloud that lingered in the sky for years. The cloud acted as a barrier to the sun. The change in environment due to the cloud eventually led to the extinction of the dinosaurs, and the end of the dinosaur age [11].

Points AgainstEdit

Volcanic Eruptions May Have Caused the Deaths of The DinosaursEdit

The Super Volcano Theory states that subsequent volcanic eruptions caused the death of the dinosaurs due to a significant amount of sulfur dioxide being released in the air which in turn affected the environment for the dinosaurs in a deadly way[12].

Research has shown that immense lava flows, rare metal, fractured crystals, and fossil records were found as evidence to support this theory[13].

Author Argues Against the Single-Cause Extraterrestrial Impact HypothesisEdit

E. J. Sargis from Yale University reviews the book Extinction and radiation: how the fall of dinosaurs led to the rise of mammals by Archibald, J. David and states that the author argues against the single-cause extraterrestrial impact of a meteorite theory, instead he suspects events such as impact, volcanoes, sea level and climate change. The author dedicates six chapters to the study of fossils from nonavion dinosaurs, Mesozoic mammals, and eutherian mammals, also of the study of origin mammals post extinction and the patterns of the K-T boundary.[14]

The Cause of Dinosaur ExtinctionEdit

Although there may have been a meteorite that started the extinction of dinosaurs, a meteorite was not solely the cause of dinosaur extinction. Climate change is the largest factor of killing off the dinosaurs. This was caused by volcanic eruption releasing sulfur dioxide into the atmosphere that changed the composition of the gases. Greenhouse gases control the weather on Earth and if there were no gases the Earth would be too cold to sustain life, but when greenhouse gases become too concentrated in the atmosphere there is a feedback loop characterized by an increase in temperature and increase in the production of greenhouse gases. Therefore; an eruption of volcanoes and possible increase in the production of greenhouse gases are two potential culprits that caused the climate to change significantly. These were the factors that led to the extinction of dinosaurs.[15]

Cretaceous/Tertiary Boundary InconsistencyEdit

In examinations of ancient plankton fossils in various areas of the planet, the studies notice that large extinctions began happening ~300,000 yrs prior to, and ~200,000 - 300,000 yrs after the Chicxulub impact event. [16] They also noticed a selective species extinction, Large species died first followed by small species which shows increased ecological stresses as a result rather than disruption in the food chain caused by the global dust.[17]

Impact is not the Reason for Mass extinctionEdit

There is evidence of impact from the Chicxulub Crater. The data is dated back 300, 000 years before the dinosaurs.[18]

The reason for the massive extinction must be a combination of the impact, volcanic eruptions, sea level and climate change, rather than the impact alone. This is an argument that has been made by Author David Archibald.

Gerta Keller is a geoscientist that has new evidence leaning toward the main factor that killed off dinosaurs being Volcanoes and not meteorites. [19]

Dinosaurs STILL alive after ChicxulubEdit

It has been previously determined that Dinosaurs were extinct due to the Chicxulub crater. This article supports findings of a deeper core that predates the Cretaceous-Tertiary (K-T) boundary by at least 300,000 years. The article also suggests that the mass extinction was a result of the K-T boundary impact and Deccan volcanism which eliminated all the dinosaurs including all other tropical and subtropical species and not just the Chicxulub crater as commonly believed.[20].

The Chicxulub impact predates the K/T mass extinctionEdit

Evidence was found that the Chicxlub impact predates the K/T boundary by about 300,000 years thus concluding the extinction of dinosaurs caused by meteorites an unlikely hypothesis. [21].

Massive Volcanic Erruptions and ExtinctionEdit

Evidence has indicated a connection between the three largest Phanerozoic mass extinctions and the three largest continental igneous provinces (LIPs). LIPs comprise of basaltic lava and igneous rock formed over a relatively brief period of time. [22]

Placental MammalsEdit

Leigh Van Valen and Bob Sloan’s theory is that due to the earth moving and continents forming, this caused mountains to form which in turn made seas to dry up and caused the climate to change. The fossil plant evidence in Montana suggests that there was a temperature decrease by approximately ten centigrades which could have occurred in the late Cretaceous period. This would have been able to cause a massive temperature decrease in the mountains which could affect the world. This also would have caused a major migration current because the dinosaurs would have headed to warm climates; such as the tropics. This theory relates to the idea that this allowed placental mammals to grow and live in the mountains, then they escaped and caused the extinction of Dinosaurs. [23]

Global Temperature Change Skews Sex RatioEdit

Studies show in current extinction patterns, that the sex ratio changes for TDS (Temperature-Dependent sex determination) animals changes based on significant climate change. This could also be true for the extinction pattern of dinosaurs which may have resulted in the preponderance of males[24].

ReferencesEdit

  1. Harmon, K. (2012). A Theory Set in Stone: An Asteroid Killed the Dinosaurs, After All. Scientific America. http://www.scientificamerican.com/article.cfm?id=asteroid-killed-dinosaurs&WT.mc_id=SA_emailfriend
  2. Rincon, P.(2010). Dinosaur extinction link to crater confirmed. from http://news.bbc.co.uk/2/hi/8550504.stm
  3. Alvarez, L. W. (06/1980) Extraterrestrial Cause for the Cretaceous-Tertiary Extinction. Science (New York, N.Y.) (0036-8075), 208 (4448), 1095. Limestones were discovered in Italy
  4. Alvarez, L. (1983). Experimental evidence that an asteroid impact led to the extinction of many species 65. Proc. Natl. Acad. Sci. 80(2), 627-642 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC393431/pdf/pnas00628-0326.pdf
  5. McLean, D. (2003).http://bcrc.bio.umass.edu/courses/spring2008/biol/biol270h/3-Discussions/12-Mass_Extinctions/12c-K-T_Extinction/12c-8_K-T_Debate.pdf
  6. Rincon, P. (2010).http://news.bbc.co.uk/2/hi/8550504.stm
  7. Fasttovsky, D., Sheehan, P. (2005).The Extinction of the Dinosaurs in North AmericaThe extinction of the dinosaurs in North America. GSA Today. 15 (3)4-9. , doi: 10:1130/1052-5173(2005)015<4:TEOTDI>2.0.CO;2 http://www.geosociety.org/gsatoday/archive/15/3/pdf/i1052-5173-15-3-4.pdf
  8. Kikuchi, R., & Vannests, M. (2010). A theoretical exercise in the modeling of ground-level ozone resulting from the K–T asteroid impact: Its possible link with the extinction selectivity of terrestrial vertebrates. Journal of Palaogeography, Palaeoclimatologym Palaeocology, 288(1-4), 14-23.
  9. Longrich, N., R., Tokaryk, T., & Field, D., J. (2011). /A critique of Mass extinction of birds at the cretaceous-palogene (k-pg) boundary. Proceedings of the National Academy of Sciences of the United States of America, 108(37), 15253-15257. doi:10.1073/pnas.1110395108 http://www.pnas.org/content/108/37/15253.full
  10. http://animals.howstuffworks.com/dinosaurs/dinosaur-extinction.htm
  11. Alvarez, L. (1983). Experimental evidence that an asteroid impact led to the extinction of many species over 65 million years ago 65. Proc. Natl. Acad. Sci. 80(2), 627-642 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC393431/pdf/pnas00628-0326.pdf
  12. The Metro. (2010).What killed the dinosaurs - asteroids, ice age or volcanoes? http://www.metro.co.uk/news/816165-what-killed-the-dinosaurs-asteroids-ice-age-or-volcanoes
  13. The Globe and Mail (2005). http://rense.com/general67/aag.htm
  14. Sargis, E.J. (2011) A review of Extinction and radiation: how the fall of dinosaurs led to the rise of mammals. Choice 48, (11) 2129.http://library.mtroyal.ca:2048/login?url=http://library.mtroyal.ca:3383/docview/877037561?accountid=1343
  15. Jourdan,F.(2010). Eruptions, Climate Change and Mass Extinction. Australasian Science, 31(3). Retrieved from http://library.mtroyal.ca:3383/docview/223692081
  16. Keller, G (1989).Extended period of extinctions across the Cretaceous/Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories Geological Society of America Bulletin, November, 1989, v. 101, no. 11, p. 1408-1419 http://gsabulletin.gsapubs.org/content/101/11/1408.short
  17. Keller, G (1989).Extended period of extinctions across the Cretaceous/Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories Geological Society of America Bulletin, November, 1989, v. 101, no. 11, p. 1408-1419 http://gsabulletin.gsapubs.org/content/101/11/1408.short or http://bulletin.geoscienceworld.org/content/101/11/1408.full.pdf
  18. Keller, G. (1988). Extinction, survivorship and evolution of planktic foraminifera across the Cretaceous/Tertiary boundary at El Kef, Tunisia. Marine
  19. Alasdair Wilkins. (2009). http://io9.com/5241410/new-evidence-suggests-an-asteroid-couldnt-have-killed-the-dinosaurs
  20. Keller, G. (2004). From The Cover: Chicxulub impact predates the K-T boundary mass extinction. PNAS : Proceedings of the National Academy of Sciences (0027-8424),101 (11), 3753. DOI: 10.1073/pnas.0400396101 http://www.pnas.org/content/101/11/3753.full
  21. Keller, G. (2004). More evidence that the Chicxulub impact predates the K/T mass extinction. Meteoritics & Planetary Science. Meteoritics & Planetary Science, 39(7), 1127-1144. https://www.princeton.edu/geosciences/people/keller/pdf/K_31.pdf
  22. Weisburd, S. (1987),”Volcanoes and extinctions: Round Two”. Volcanoes and extinctions: Round Two. Science News, 131(16), 248-250. http://www.jstor.org/stable/pdfplus/3971631.pdf
  23. by the Editors of Publications International, Dinosaur Extinction/Climate Change Theories, Animal Planet,
  24. A Critique of Environmental versus genetic sex determination: a possible factor in dinosaur extinction?, David Miller, Ph.D.a Jonathan Summers, Ph.D.b and Sherman Silberc, April 1, 2004, Abstract http://www.infertile.com/inthenew/sci/2004-04-01-Fert-Steril.htm