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Precursor to KT - Species in decline?
                                                      Many scientists believe around...
Yum
                                                      Small mammals preying on dinosaur eggs have
                    ...
record to date the period of the species’ existence.    to ten billion Hiroshima bombs(Strahan 2004). The
The problem with...
A sample of Shocked Quartz found at Chixculub

                                                                           ...
may have played out at the time of the KT               Further proof – Stone In Peculiar Places
boundary.                ...
photosynthesis in plants. In addition, Deccan Trap                        struck at the time of the KT boundary. There is
...
and hope that in the coming years, additional
improvements to the fossil record will give us a
better picture of what was ...
Jack Oughton - KT Extinction Article.doc
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Jack Oughton - KT Extinction Article.doc

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Transcript of "Jack Oughton - KT Extinction Article.doc"

  1. 1. Precursor to KT - Species in decline? Many scientists believe around ten million years before the KT boundary, the environment began to get markedly more hostile to life. The lush coastal planes on which dinosaurs depended began to turn arid, as sea levels fell worldwide. Their natural habitat was disappearing. Between ten million and three million years before the KT boundary, the dinosaurs seem to have suffered a huge decline. One interpretation of the fossil record is that forty percent of dinosaur species went extinct before the transition. In an interview with the BBC, David Archibald, Professor of Evolutionary Biology at San Diego State, spoke of the period leading up to the boundary. ARCHIBALD: “ Organisms are adapted for a certain type of environment and when those The KT mass extinction? conditions disappear those organisms disappear… we come up to about one to three million years before the end of the Cretaceous and we've got a group that seems to be vulnerable to any kind of extinction events that might be occurring at that time.” Global Warming Could Have Been Contributed To by Organic Sources Increasing concentrations of methane in the Earth's atmosphere would force changes to the earth’ s climate on a global scale. Aside from methane coming from seismic sources, the suffocating gas could also originate organically. This organic methane would originate from increased numbers of deep-sea algae deposits and from the digestive processes of plant-eating dinosaurs. Increasing water temperatures could have caused a destructive feedback loop; Algae breeds better in warmer temperatures , and the greater the quantities of algae, the more methane, and consequentially the warmer the environment would become Fossil evidence also suggests that Plankton What was it? decreased in number during the Tertiary period. This may help explain the destruction of many The KT mass extinction event was a large-scale marine food webs which relied on them. mass extinction of animal and plant species in a relatively short period of time. There is a Adapting To The Change [Or Not..] noticeable boundary indicated in the fossil record In the changing climate, animals better able to [known as the KT boundary], which is marked by burrow, or semi aquatic in nature would have had a mass extinction topping 17 families per million a higher chance of surviving. years [around 15 families per million years above Harsh conditions would have had a damaging effect the average]. It occurred roughly 65 million years on all life, however creatures whose food chains ago. were based on detritus had a reasonable chance of survival. K is the derived from the German name Kreidezeit, which translates as the Cretaceous Period. T is the abbreviation for the Tertiary Period (an outdated description for the period of time now covered by the Paleogene and Neogene periods). The KT boundary marks the transition between these two periods.
  2. 2. Yum Small mammals preying on dinosaur eggs have been suggested as a contributor of the K-T extinction. However it does not explain why so many other species went extinct around, or the iridium chemical anomalies in the K-T layer, and could therefore be a contributor, not a cause to the ongoing extinction. Repenomamus robustus was an opossum-sized mammal about 1 m long and weighing around 14-15 kg living around 130 million years ago. A Chinese fossil of it was discovered a few years ago with the remains of a juvenile psittacosaur in its stomach area. This is direct evidence that some mammals fed on small vertebrates, including young dinosaurs. On this diagram the KT boundary [the last mass extinction event] marks the termination of the dinosaur, pterosaur and mosasaur genetic trees. Food web disruptions – a threat to dinosaurs? In the late Cretaceous, photosynthesizing organisms, including phytoplankton and land plants, formed the foundation of the food chain. Evidence suggests herbivores declined when the flora they depended on for food became scarce; recently evolved flowering plants may have outcompeted many of the non-flowering species Artist’ s impression of a Repenomamus – with its that the dinosaurs relied on for food. . dinner. Consequentially, predators higher up the food Source: http://my.opera.com/nielsol/blog/index.dml/tag/fossils chain such as Tyrannosaurus rex also suffered as prey numbers diminished. The origin of Birds A number of groups of Neornithine birds [the At the end of the Cretaceous there seem to have precursors to modern avian species] survived the harsh conditions of the KT event as a result of been no purely herbivorous or carnivorous animals. their abilities to dive, swim, or seek shelter in Many more species that were Omnivores, water and marshlands. Many species of birds can insectivores and carrion-eaters survived the build burrows, or nest in tree holes or termite extinction event, perhaps because of a more diverse nests, all of which provided shelter from the diet which would act as insurance against declining environmental effects at the KT boundary. food sources. Of the creatures that survived the extinction, most fed on insects, worms, and snails. Ecological Niches This is significant as this food source fed on dead With the decline of the dinosaurs, evolutionary plant and animal matter. Scientists hypothesize pressures changed. Long-term survival past the that this detritus based food web fared better than difficult conditions at the boundary was easier for the plant based food chains as there would not the remaining species as they could now fill niches have been a significant fall in the amount of left empty by the extinction of the dinosaurs. In detritus [dead organic matter] available for the Darwinian sense, competition decreased for the sustenance. surviving species, thus making it easier for them to find food and the resources they needed to It has been hypothesized that with levels of oxygen propagate. falling, smaller animals, and animals with more efficient respiratory systems [such as small Fossil Record Problems – The Signor Lipps mammals – which may have required less oxygen Effect than much the larger dinosaurs] would have been Although we have a lot of evidence for the better able to adapt to these new conditions. explanations put forward, we are using the fossil
  3. 3. record to date the period of the species’ existence. to ten billion Hiroshima bombs(Strahan 2004). The The problem with this is that the fossil record is so result would have been an immediate loss of life incomplete that most extinct species probably died from the impact event. The following ‘ nuclear out long after the most recent fossil that has been winter’ would have caused an even greater loss of found. However as the fossil record is the best way life as plants, unable to photosynthesize, died, and of dating we have no other option. We also cannot the food webs on which they depended collapsed. make any accurate estimations on how long a species may have survived after the last fossil is found. Scientists have also found very few continuous beds of fossil-bearing rock which cover an unbroken time range from several million years before the K– T extinction to a few million years after it. Unfortunately, this means there are a lot of temporal gaps we have to fill in with guesswork, due to our dependence on this record. The KT Boundary – an impact event? Artist’ s impression of the time immediately after an impact event. A plume of vaporised water punctures the atmosphere into space. Source: http://www.sciencedaily.com/images/2009/04/090427010803.jpg Where did it impact? - About Chicxulub The KT boundary is the obvious on this rock – marked by the claystone later in the middle - it contains 1000 times more iridium than the upper and lower layers. Some believe that the KT mass extinction was caused by a huge asteroid striking earth. It is rare for an asteroid of a large enough size pass through the earth’ s atmosphere intact, but when such events happen, the results are cataclysmic. Scientists believe an object 10 km wide slammed into the earth on the tip of the Yucatan Peninsula, in the Gulf of Mexico. It is thought that upon Source: http://web.ukonline.co.uk/a.buckley/dino.htm striking, the comet would have sent a blanket of dust and steam into the atmosphere; this emission of dust and particles would have resulted in environmental changes similar to a nuclear winter, Chicxulub [Nahuatl: “ The Tail of the Devil” ] with this new artificial atmosphere of dust blocking Crater is an ancient impact crater buried out radiation from the sun and causing a planet underneath the Yucatan peninsula, with its center wide dimming and cooling. located approximately underneath the town of Chicxulub, Yucatán, Mexico. It is thought to be The impact blast have caused huge forest fires, the impact site of the impactor which is believed to immense tsunamis in all directions radiating from have contributed to the KT extinction. the crash site, severe storms due to meteorological disruption, and eliminated all sunlight for a period of 6 months under an ashen sky. The energy it unleashed on impact would have been equivalent
  4. 4. A sample of Shocked Quartz found at Chixculub Shattered or "brecciated" rock Translated from Italian a breccia is “ a stone made by cemented gravel” – which is exactly what they are. Though there are a many varieties of brecciated rock, such as types formed by geological processes, breccias formed by an impact event are quite distinct. They are layers of rock crushed together by compressive weight, exerted by the Topographical image of the Chicxulub crater, huge pressure of an impact event. This showing local gravitational anomalies [note the compressive deformation is similar to the process blue]. that creates shocked quartz. Source: http://www.astro.uio.no/ita/nyheter/katastrofer_0901/chicxulb.gif In the winter of 2001/2 The Chicxulub Scientific Evidence at Chicxulub Drilling Project (CSDP), Mexico, dug up an area of There is a great deal of evidence that corroborates impact melt and breccias in the Yax-1 borehole 100 our theory that Chicxulub was formed by an m thick. (Kring et al. n.d.) immensely destructive impact event. Evidence for Chicxulub is also evidence for an impact event Further evidence comes from gravitational and contributing to the extinction of the dinosaurs, as magnetic anomalies in the area. Gravitational we know through detailed statistical modelling anomalies on the earth’ s surface suggest there are [and the occasional thermonuclear test] that any variances the local magnetic field caused by such impact would have disastrous consequences differences in the underlying mass of the earth. for life. Such changes are deemed unnatural, as the geological processes that created the earth generally created a distribution of land uniform Shocked Quartz Shocked quartz is formed when immense pressures enough to result in a gravitational field with very little in the way of variety .One explanation for cause a deformation of the internal structure of a quartz crystal. Shoemaker discovered that it often these anomalies could come from the idea that material has either been excavated or deposited by formed in nuclear bomb testing sites. As impact events release comparable amounts of energy, destructive intervention, such as an impact event. finding shocked quartz in a crater strongly suggests that it was not formed by volcanic activity, as Ejecta pressures in a volcano are not high enough to cause Ejecta is the material released by an impact event. the deformation. Ample shocked quartz has been As an impactor strikes the earth’ s surface, it found at Chicxulub and the accompanying crash displaces a certain amount of material, which is sites(Smit 2003), from this we can deduce that blasted out with great force and lands elsewhere, Chicxulub is not a geological formation. often far from the impact site. Due to the extreme conditions of an impact event, ejecta is often very noticeable, even far from it’ s point of origin. Ejecta from Chixulub have been located in the Cayo District of central Belize, about 500 km southeast of the Chicxulub impact crater. (Ocampo et al. 2003) Multiple Impacts? The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 demonstrated that gravitational interference can fragment an impactor, allowing for multiple impacts over a period of a few days if the comet should collide with a planet. This scenario
  5. 5. may have played out at the time of the KT Further proof – Stone In Peculiar Places boundary. The Chicxulub impact [which impacted on water] would have caused a Tsunami that must have Other craters of around the same age as churned up billions of tonnes of sand from the Chicxulub have been discovered, all between coast and dumped it on the ocean bed. This latitudes 20°N and 70°N. They include the became the sandstone and when the sea level fell, Silverpit crater in the United Kingdom, and the the rock was exposed. Boltysh crater in Ukraine. They are much smaller than Chicxulub but are believed to have been have The work of Hildebrand, a graduate student at the been caused by objects many tens of metres across University of Arizona, found that such sandstone striking the earth. This has led to the hypothesis deposits occur in many locations, but seem to be that the Chicxulub impact may have been only one concentrated in the Caribbean basin. of several impacts that happened all around the time. A Final Clue One of the largest pieces of evidence of In 1997, palaeontologist Sankar Chatterjee drew environmental destruction from the KT period was attention to a much larger 600 km (370 mi) Shiva a high concentration of fern spores. Ferns flourish crater, located in the Indian Ocean. Due to it’ s whenever all other plants have been killed off by monstrous size, it was tentatively suggested that some environmental devastation. The spores are to this could have been an impactor in the KT be found well distributed on the geological KT scenario. However, there is currently argument in boundary(Fleming & Nichols 1990). the astrogeological field as to whether Shiva was formed by an impact at all(Sankar). Alternative theories There is the possibility of more concurrent impacts, however any craters that might have The event could be linked to a combination of formed in the Tethys Ocean would have been causes, as many of these are linked. erased by tectonic events related to northward drift of Africa and India. Environmental changes and the Deccan Traps. More Proof – Rock Displacement, Shocked Quartz For about half a million years before the KT And The Iridium Anomaly boundary, the world suffered a period of extremely destructive vulcanism. Vast areas of the surface where covered by molten lava. A million cubic Iridium is a transition metal which is extremely kilometres of material spewed out in what are rare on the earth’ s surface but common in known as the Deccan Traps. asteroids. Iridium is rare on the earth’ s surface as it often forms chemical bonds with iron, which as a Information points to the 600 meters (2000 feet) of heavy element, sinks to the earth’ s core. lava pouring out of them in as little as 30,000 years. This is enough to have possibly released a Distributed through the material that makes up climate-altering amount of sulphur gases, and is the KT layer there is an unusually high most probably a very significant contributor to the concentration of Iridium. This strongly suggests climate change that is thought to have occurred. that an object with a high concentration of iridium (Geological Society Of America 2005) impacted the earth with enough force to disperse the materials of which it was made all over the Additional evidence suggests that most of the surface of the planet. This same iridium rich dust Deccan Traps flood basalts were erupted in a <1 could have been responsible for the nuclear winter Million year interval which coincided with the K/T that blanketed the atmosphere and was so deadly boundary. The global environmental effects from to life. This layer is also very rich in soot. this volcanism could be similar to a large impact, such as global dimming due to particle release into “ … it contains enough soot to correspond to the atmosphere. However, the timescale of the two burning down all of the forests of the world. This processes would be different. The full consequences suggests that massive fires were touched off at the of an impact event may only take a few months to time of impact” (Hartmann n.d.). manifest, whereas the effects from volcanism would be spread over at least a few hundred thousand This soot evidence suggests forest fires of an years. Therefore resolving these hypotheses unparalleled scale. Such a quantity of huge fires requires estimating the duration of the K/T event. could have caused a large conversion of oxygen to Unfortunately most chronological techniques do carbon dioxide, and thrown up even more detritus not have sufficient resolution to date geologically into the sky. This would have the effect of making ‘ instantaneous’ events environmental conditions even more inhospitable. Air would harder to breathe, and declining light The Deccan Traps could have caused extinction would result in falling temperatures and available through several mechanisms, including the release light for plant photosynthesis. of dust and sulfuric aerosols into the air which might have blocked sunlight and thereby reduced
  6. 6. photosynthesis in plants. In addition, Deccan Trap struck at the time of the KT boundary. There is volcanism might have resulted in carbon dioxide also no doubt that this impactor was powerful emissions which would have increased the enough to severely disrupt the ecology of the earth. greenhouse effect when the dust and aerosols What is called into question is the idea that this cleared from the atmosphere. impact could be the sole cause of the extinction of so many species. Evidence suggests that other causes could have played their part. A gradually worsening environment caused by increased seismic activity in regions such as the Deccan Traps. Darwinian pressures, due to disruption introduced by innovative newly evolved species, such as small, devious mammals. Lastly, additional speculation coming from astronomical explanations such as variations in the earth’ s orbit and gamma ray bursts could also bear some scientific weight, given time and a little more proof. Perhaps Chicxulub was the finishing blow to a dying species? Jan Smit, Professor of Event Stratigraphy at the The Deccan Traps – notice the ridged surface, University of Amsterdam and an acknowledged which geologists believe was caused by the layered expert on sedimentology, writes on his personal accumulation of thousands of years worth of lava. Source: http://farm4.static.flickr.com/3185/2575165118_c8c6c29282_o.jpg website; Disease SMIT: “ there is evidence for a decline of some of Another, possibly far flung explanation has been the biotic groups becoming extinct at or near the linked to falling sea levels. As sea levels fell, more KT boundary, but decline is on different and more land bridges started to appear on the timescales, and attributable to various non-impact earth. The dinosaurs would have been able to cross related causes (cooling, Deccan traps). There is these bridges into new territory, bringing their little doubt however, that the mass- and final microbes with them. Millions of years of careful extinctions all occur very close to and at the KT evolution would mean that the migrating dinosaurs boundary, suggesting a cause and effect where immune to these bacteria, whereas dinosaurs relationship with the Chicxulub impact. These native to the regions they were colonizing were effects, despite almost two decades of research, are not. This could have resulted in a kind of still poorly understood” (Smit n.d.). unintentional biological warfare, in which the species native to the regions where assailed by ARCHIBALD: “ Six million years prior to the KT bacteria which they had not time to evolve boundary there were about twenty species of immunity against, similarly, dinosaurs migrating to ammonites in the world's oceans. Three million these new regions would also be entering a years before the KT boundary there were only territory full of microscopic enemies unknown to fifteen or so and one million years prior to the KT their immune systems . Although perhaps far boundary we have less than half of what we flung, this bacterial invasion has actually been seen started out with, we have less than ten species so documented in humans. Around the time that the extinction event has already been going on for Europeans first visited the new world it has been millions of years. We see the same pattern in the estimated that European disease wiped out 95 fish record, in the terrestrial reptile record, even in percent of America's pre-Columbian the mammal record. All of these groups were population(Diamond 1999) undergoing an extinction event for millions of years and it would be absolutely amazing to me if Orbital Variation dinosaurs weren't undergoing.. the same sort of Changes in the Earth's orbit that could have been long term extinction… Clearly dinosaurs were responsible for climactic variations which incredibly unlucky at the end of the contributed to a more hostile environment. In this Cretaceous to have all three things happen at scenario, the dinosaurs couldn't adapt to the cold, the same time.” but the furry mammals could. This theory is consistent with the climate in the late Cretaceous; So we have established that the KT boundary is toward the end of this period, there was a drop in not a single point in time, and is instead a period sea level, causing land exposure on all continents,. with a length not yet agreed upon by scientific From the upset of the global thermodynamic consensus. We must make a distinction between system came more variance in seasonal conditions, the KT impact event and the KT extinction, as and greater extremes between equatorial and polar evidence suggests they are not mutually exclusive. temperatures. As of yet proof is not abundant for The KT impact event is clearly a contributor to this theory and it would be exceptionally hard to the KT extinction, but cannot be deemed the sole test this hypothesis using the fossil record. cause. Lastly, as our evidence from this time is sparse and relies on the fossil record, which is Conclusion – The Experts Speak incomplete at best, we cannot draw any certain It seems there is ample proof that an asteroid conclusions. We can only offer more hypotheses
  7. 7. and hope that in the coming years, additional improvements to the fossil record will give us a better picture of what was happening at the time. – Jack Oughton Bibliography) Diamond, J., 1999. Guns, Germs, and Steel: The Fates of Human Societies (Paperback) 1st ed., W. W. Norton & Company. Fleming, R. & Nichols, D.J., 1990. The fern-spore abundance anomaly at the Cretaceous-Tertiary boundary: A regional bioevent in western North America. In Extinction Events In Earth History. Springer Berlin / Heidelberg, pp. 347-349. Geological Society Of America, 2005. India's Smoking Gun: Dino-killing Eruptions. Sciencedaily.com. Available at: http://www.sciencedaily.com/releases/2005/08/050810130729.htm [Accessed March 2, 2010]. Goldberg, C., Unique Facts about Mexico: Chicxulub Crater. Sheppard Software. Available at: http://www.sheppardsoftware.com/Mexicoweb/factfile/Unique- facts-Mexico4.htm [Accessed February 22, 2010]. Hartmann, W.K., The KT-boundary Impact. The Impact That Wiped Out The Dinosaurs. Available at: http://www.psi.edu/projects/ktimpact/ktimpact.html [Accessed March 2, 2010]. Images-Of-Elements.com, Hi-Res Images of Iridium. Images Of Elements. Available at: http://images-of-elements.com/iridium.php#a [Accessed February 22, 2010]. Kring, D.A. et al., Impact lithologies and their emplacement in the Chicxulub impact crater: Initial results from the Chicxulub Scientific Drilling Project, Yaxcopoil, Mexico. Meteoritics & Planetary Science, 39, 879-897. Mukhopadhyay, S., KT impact. Welcome to the Noble Gas Laboratory. Available at: http://www.people.fas.harvard.edu/~mukhop/KT.htm [Accessed February 27, 2010]. Ocampo, A. et al., 2003. New Location of Chicxulub's Impact Ejecta in Central Belize. Sankar, C., Multiple Impacts at the KT Boundary and the Death of the Dinosaurs. Journal of Geodynamics, 31-54. Smit, J., 2003. (7) CHICXULUB IMPACT CRATER AND THE K/T MASS EXTINCTION, REVISITED. Available at: http://www.geo.vu.nl/ ~smit. Smit, J., Global mass-extinction at the KT boundary. Space Telescope European Co-ordinating facility. Available at: http://www.stecf.org/~ralbrech/amico/intabs/smitj.html [Accessed February 28, 2010]. Strahan, D., 2004. BBC Horizon: What Really Killed The DInsoaurs? BBC: Horizon - What Really Killed The DInosaurs? Trexler, D., 2000. Dinosaur Treks - Extinction Theories. Thinkquest.org. Available at: http://library.thinkquest.org/C005824/extinction.html [Accessed February 22, 2010].

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