Mass Extinctions on the Earth

Intro:

  • Sixty-five million years ago, some phenomenon triggered mass extinctions on the lands and in the oceans so profound that they define the geological boundary in between the older Mesozoic Era, frequently known as the “Age of Reptiles,” and the contemporary Cenozoic Era, the “Age of Mammals.”
  • On a finer scale, the extinctions define the boundary in between the Cretaceous (geological symbol, “K”), and Tertiary (“T”) periods. This mass extinction is generally referred to as the K-T extinctions. The dinosaurs became extinct throughout the K-T mass extinction. To examine how the K-T extinctions fit into a broader perspective, please see the
  • The result in of the K-T extinctions is one particular of the fantastic mysteries in science, and several scientists have proposed theories to account for it. Theories span a vast spectrum of causes which includes: sea level transform, supernova explosions, climate change, and on and on.
  • Beginning in the 1980s, two new theories became the subject of an intense scientific debate. They are the K-T impact extinction theory originated by the Nobelist physicist, Luis Alvarez, and his group, and the K-T Deccan Traps extinction theory, which, for short, is named volcano-greenhouse theory.

    Details of the Effect Theory

  • In the mid-late 1970s, Luis Alvarez and his impact group began looking for the cause of the K-T extinctions.
  • His proof of influence was enrichment of the chemical, iridium, in a thin layer of clay a couple of centimenters thick at the K-T boundary. His original theory held that a giant asteroid struck earth 65 million years ago, blasting so much dust into the atmosphere that it blocked out sunlight, and plunged earth into the blackness and cold of a sudden, brief-duration, “effect winter.”
  • According to Alvarez theory, the worldwide blackout triggered extinctions among the plant kingdom, and then among herbivores that depended upon plants for food, and then amongst the carnivores that ate the herbivores.
  • These smaller animals that could hide and hibernate till the sun came out again need to have sruvived and formed the animals that there are now.
  • There is other evidence for this theory : there is a layer of iridium found on top of the fossils which can be located all more than the world. this is crucial becouse there is a lot of iridium on asteroids while on earth it is only deep down inside the crater.

    Specifics of the Volcano Theory:

  • One more less preferred theory to explain the disappearance of the dinosaurs suggests that a drop in the oxygen levels in…

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