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The K-T Extinction

The K-T Extinction. Christina Davis Katie Peth 19 April 2012. K-T Extinction. K-T Extinction. K Abbreviation for Cretaceous Period, derived from the German name Kreidezeit T Abbreviation for the Tertiary Period

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The K-T Extinction

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  1. The K-T Extinction Christina Davis Katie Peth 19 April 2012

  2. K-T Extinction

  3. K-T Extinction K • Abbreviation for Cretaceous Period, derived from the German name Kreidezeit T • Abbreviation for the Tertiary Period • historical term for period of time covered by the Paleogene and Neogene periods http://evolution.berkeley.edu/evolibrary/images/interviews/extinction_graph3.gif http://en.wikipedia.org/wiki/K–T_boundary

  4. K-T Extinction • Also referred to as the Cretaceous–Paleogene extinction event • Approximately 65.5 million years ago • Associated with geological signature • K–T boundary: thin band of sedimentation found in various parts of world http://en.wikipedia.org/wiki/K–T_boundary

  5. http://en.wikipedia.org/wiki/K–T_boundary

  6. K-T Extinction • Numerous groups of organisms went extinct, most notably the non-avian dinosaurs. • Non-avian dinosaur fossils are only found below K-T boundary indicating they became extinct during boundary event • Very small number of dinosaur fossils have been found above the K–T boundary (reworked fossils) • eroded from their original locations then preserved in later sedimentary Littlefoot, Cera, Spike, Ducky, Petri http://en.wikipedia.org/wiki/K–T_boundary

  7. Fossils Psittacosaur meileyingensis Triceratops Coelophysis bauri Duck-billed Dinosaur

  8. The T-Rex • http://www.youtube.com/watch?v=PSI8nP0m24M http://www.popcrunch.com/wp-content/uploads/2011/05/t-rex-jurassic-park-500x301.jpg

  9. Others That “Moved On” • Mosasaurs, plesiosaurs, pterosaurs, various plants and invertebrates became extinct Prognadothon Plesiosaur fossil Juvenile Plesiosaur Taniwhasaurus

  10. More Casualties Rudist Bivalve Belemnites (cephalopod) Azhdarchidae (Pterosaur) Ammonite Fossil

  11. Mammals! • Mammalian clades passed through boundary with few extinctions (see Katie’s shirt) • Mammalian clades then thrived and evolved, along with other species (more on that later!) http://images.nationalgeographic.com/wpf/media-live/photos/000/089/cache/mammal-evolution_8984_600x450.jpg

  12. Potential Causes • One or more catastrophic events? • Asteroid impacts? • Increased volcanic activity? • Several impact craters and massive volcanic activity have been dated to the approximate time of extinction • These events would have released massive amounts of dust and ash released into the atmosphere • Reduced surface sunlight • Hindered photosynthesis • Disruption of Earth’s biosphere MacLeod, N. J. Geo. Soc. 1997, 154, 265-292.

  13. Controversy • Many believe the extinction was more gradual from the sea level and climate changes, and aggravated by impact events or increased volcanic activity • Length of time for extinction to occur is controversial • Signor-Lipps effect: the fossil record is so incomplete that most extinct species probably died out long after the most recent fossil that has been found. • There are very few continuous beds of fossil-bearing rock from before and after K-T extinction • Several million years before to few million years after http://en.wikipedia.org/wiki/K–T_boundary

  14. Controversy http://blog.beliefnet.com/jesuscreed/files/import/assets_c/2010/02/Extinction-thumb-333x344-11363.jpg http://scienceblogs.com/gregladen/dinosaur_extinction_theory.jpg

  15. Causes • Impact • Alvarez Impact Hypothesis • Chicxulub Crater • Deccan traps • Multiple impact • Maastrichtian sea level regression • Supernova hypothesis • Multiple causes http://en.wikipedia.org/wiki/K–T_boundary

  16. The Impact The Impact http://www.dinosaurfact.net/images/dinoextinctpic.jpg http://www.shivanjaikaran.com/files/ic.c8466846c279a1462f992708570eddfd.xasteroidimpact,j.jpg

  17. Alvarez Hypothesis • Mass extinction of dinosaurs (etc.) caused by impact of large asteroid on Earth 65 million years ago • Named for Nobel-prize winning physicist Luis Alvarez who first suggested theory in 1980, along with geologist son Walter Alvarez and chemists Frank Asaro and Helen Michels http://en.wikipedia.org/wiki/Alvarez_hypothesis

  18. Evidence? • K-T boundary sedimentary band all over the world has iridium ranging from 20-160 times normal amount. • Iridium is rare in Earth’s crust, but abundant in asteroids/comets • Also found chromium isotopic anomalies similar to those found in carbonaceous chondrites, along with shocked quartz granules and tektites. Alvarez, L.W. Science. 1980, 208, 1095-1108.

  19. Alvarez Impact Able to calculate size of meteor Would have to be 10-15 km in diameter (size of Mars moon Deimos, or Manhattan) Impact of that size would have an incredible amount of energy 1 x 108 megatons, 2 million times greater than most powerful thermonuclear bomb tested! Alvarez, L.W. Science. 1980, 208, 1095-1108.

  20. Chicxulub Crater http://www.lpl.arizona.edu/undergrad/classes/spring2011/Hubbard_206/Lectures4/Apr19.htm

  21. Chicxulub Crater Impact site buried underneath Yucatán peninsula in Mexico, discovered by geophysicist Glen Penfield in the late 1970s. Took about 20 years to fully investigate crater, with help from Alan Hildebrand. Evidence for impact: Shocked quartz Tektites Gravity anomaly http://en.wikipedia.org/wiki/Chicxulub_crater

  22. Alvarez Impact • Created sunlight blocking dust cloud • Affects photosynthesis, leading to extinction of plants, phytoplankton and other organisms dependent on it. • Sulfur aerosols (12 years to dissipate) • 10–20% reduction of solar transmission • Global firestorms exacerbated by high O2 concentration • Increase in CO2, greenhouse effect once cloud settled • Reduced global temperature (impact winter) • Acid rain (relatively minor impact) + megatsunamis! Kring, D.A. Astrobiology. 2003, 3, 133-152

  23. Alvarez Impact 2007- Hypothesis that impact forming Chicxulub crater was caused by asteroid from Baptistina family of asteroids 2011 WISE study begs to differ. 2010- 41 scientists reviewed 20 years of literature to rule out massive volcanism as cause. Also endorsed that the asteroidal impact at Chicxulub crater as being the cause of the extinction The collision would have released the same energy as 100 teratonnes of TNT (420 ZJ), over a billion times the energy of the bombs dropped on Hiroshima and Nagasaki Still controversy on whether a single impact was the sole cause.

  24. Deccan Traps http://johnstodderinexile.files.wordpress.com/2006/10/deccan-flood-basalts.jpg

  25. Deccan Traps • Large igneous province located on the Deccan Plateau of west-central India • One of the largest volcanic features on Earth • Multiple layers of solidified flood basalt • more than 2,000 m thick with an area of 500,000 km2 and a volume of 512,000 km3 http://en.wikipedia.org/wiki/Deccan_Traps

  26. Basalt • Common extrusive volcanic rock

  27. Deccan Traps • “Trap” is derived from the Swedish word for stairs and refers to the step-like hills forming the landscape of the region. • Release of volcanic gases, particularly sulfur dioxide, during formation of traps contributed to contemporary climate change • Average fall in temperature of 2 °C in this period http://en.wikipedia.org/wiki/Deccan_Traps

  28. Deccan Traps http://upload.wikimedia.org/wikipedia/commons/3/31/Deccan_Traps_volcano.jpg

  29. MULTIPLE IMPACT MultipleImpact Theory • http://images.nationalgeographic.com/wpf/media-live/photos/000/010/cache/mass-extinction_1077_600x450.jpg http://images.nationalgeographic.com/wpf/media-live/photos/000/010/cache/mass-extinction_1077_600x450.jpg

  30. Multiple Impact Theory • Simultaneous impacts around the K-T boundary • Asteroids/comets • Boltysh Crater (Ukraine) • Silver Pit Crater (North Sea) • Shiva Crater (Indian Ocean, controversial origin) • Could have had more formed in Tethys Ocean obscured by tectonic effects. http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event

  31. Shiva Crater 500 km in diameter, hypothesized by Sankar Chatterjee to be result of impact with 40 km asteroid. Unusually rectangular, with large amounts of alkaline melt rocks, shocked quartz, and iridium Many remain unconvinced; “Shiva Crater” not recognized as an impact crater by the Earth Impact Database. http://en.wikipedia.org/wiki/Shiva_crater

  32. Maastrichtian Sea Level • Maastrichtian was the final part of the Cretaceous period • Between 72 to 66 million years ago • Exposed rock layers do not show the kind of erosion, tilting, distortion and other geologic patterns that are common with formation of mountains. • Evidence that sea levels fell dramatically during this time • Hypothesis: mid-ocean ridges became less active and thus sunk under their own weight causing marine life form extinction http://www.helium.com/items/1409742-why-dinosaurs-became-extinct-the-k-pg-extinction-theories

  33. Supernova Hypothesis • Cosmic radiation from a nearby supernova explosion • Fallout from a supernova explosion should contain 244Pu, the longest-lived plutonium isotope (half-life of 81 million years) • If this hypothesis were correct, detectable traces of 244Pu should be detected from rocks deposited at the time • However, there is an absence of 244Pu, disproving this hypothesis http://en.wikipedia.org/wiki/K–T_boundary

  34. Multiple Causes? • Mixture of previously mentioned causes

  35. I Will Survive! Microbiota Radiolaria, Diatoms, benthic foraminifera Marine Invertebrates Brachiopods, nautiloids, coleoids Fish 80% of cartilaginous fish 90% of teleost fish • http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html

  36. I Will Survive! Terrestrial Invertabrates Terrestial Plants Paleocene recovery of plants began with recolonizations by fern species Saprotrophic organisms Polyploidy Amphibians • http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html

  37. I Will Survive! Non-archosaur reptiles Testudines (turtles) Lepidosaurs (snakes and lizards) Choristoderes Archosaurs Crocodilians Dinosaurs (Birds) Mammals! Diversification stalled. • http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html

  38. Conclusions • Most accepted reason is the Alvarez Impact Theory • Most likely mixture of this impact and volcanic activity • Supernova not supported with scientific evidence • Ability to survive depended on food source, size, environment • Feed on snails or other detritus species • Tiny is best • Stable to environmental changes

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