The Collapse Of The Mesozoic Biosphere Flashcards
How many marine species became extinct?
80-90% of marine species including ammonites and marine reptiles.
What about on land?
Few creatures over 25 kg survived. Exceptions include alligators and crocodiles.
Who brought into light the possibility of extra terrestrial impact?
Luis and Walter Alvarez.
Describe the clay layer the Alvarez team was investigating in Gubbio, Italy.
The clay layer was directly above last Cretaceous sediment and was enriched with iridium. This iridium anomaly was found in other places around the world as well.
How does iridium relate to extra terrestrial impact?
Iridium is known to exist in higher concentrations in extra-terrestrial objects such as asteroids. Alvarez suggested that the clay layer enriched in iridium had been produced by a meteor or comet over 10 km in diameter impacting the Earth.
Describe further evidence regarding extra terrestrial impact.
Fern spores were incorporated into sediments. “Spore spike.”
Soot layers were found, giving evidence to global fires.
Tektites are composed of natural glass and are produced during impact events.
Shocked quartz is formed when rock is shattered during high energy impact.
Massive tsunami deposits found at K/P boundary.
Describe the Chicxulub Impact Crater.
In the Yucatan Peninsula of Mexico. Over 180 km in diameter. The object responsible for this crater had a shallow angle of entry around 20 - 30° and is estimated to have been at least 10 km across.The energy released by the impact was equivalent to 6.2 x 10^7 tons of TNT causing about 100 km3of rock to be vaporized and released to the atmosphere. Material that wasn’t instantly vaporized was thrown out of the crater (theejecta) and was deposited to the northwest of the impact site.
What were the initial effects of the impact?
Sonic boom, detonation, pulse of intense heat and light that would vaporize everything that was close and causing organic material to combust farther away. Would have caused Earth to ring like a bell with seismic energy. Shockwave would carry superheated rock debris and molten material and deposit a thick layer of ejecta in Mexico and the southern states. It would also create a large tsunami.
Describe the long term effect of global temperature.
Tons of dust and debris would be in the atmosphere and it would stay suspended, cooling the Earth and stopping plants from photosynthesizing. Food chain would collapse. After dust settles, water vapour would still be in the atmosphere, preventing heat from leaving Earth, creating rise in temperature. Water vapour would be removed from rainfall, but the release of greenhouse gases would last for a long time.
Describe the long term effect of atmospheric composition.
The impact would’ve physically burnt the air, combining oxygen and nitrogen to form oxides of nitrogen that would be dissolved in water in the atmosphere to form dilute nitric acid. This falls as acid rain. Also, evaporites rich in Gypsum (CaSO4) formed in Yucatan area beforehand. When Gypsum is vaporized, it produces SO2 which combines with rain to produce sulfuric acid. More acid rain.
What did acid rain effect?
Acid rain did not affect large animals directly, but it affected the soil and ocean surface, negatively affecting plants and plankton. It would disrupt the food chain.
What other factors besides the impact could have caused extinction?
Pangea fragmenting would have caused change in ocean circulation and climate.
Climate affected by volcanic activity (Deccan Traps in India).
What was poisoning the Cretaceous atmosphere?
Volcanic activity.
What effect did volcanic gas have on the T-Rex?
Acidic pollution that prevented egg shells from forming properly.
What was the early warning of the approaching Chicxulub?
Shooting stars.
