Cosmic Impacts and Life on Earth

Cosmic Impacts and Life on Earth


 You are visitor number   since 18 June 1999 


These are lecture notes from an experimental non-majors biology class taught in 1995 by
Bruce Walsh, University of Arizona.
Other lectures of potential interest:

  • Origins of life

  • Extinctions
  • Genetics class lecture notes

    • Two separate tales to be joined
      • Walter and Luis Alverez (1977)
      • looking at world-wide clay deposits
    • Dave Raup and Jack Sepkoski (1980)
      • Looking at extinction rates of marine invertebrates

    The Alverez’s tale

  • The Alverez Iridium anomaly
    • Around the world is a thin band of clay at the Cretaceous-Tertiary (KT) boundary
    • This band is highly enriched for Iridium (Ir)
  • Iridium
    • A rare-earth element
    • Rare in EarthÕs crust
    • Common in meteorites
    • Can be extruded by Volcanoes
  • What was the source?
    • Extra-terrestrial impact Vs. volcanoes
    • comet/asteroid impact
    • massive series of Volcanic eruptions
  • Impact rather than Volcanic origin suggested
    • microtektites
      • very small glass spheres caused by very high velocity impact (impact, Not volcanic)
      • strewn fields worldwide
    • shock quartz
      • quartz grain with multiple sets of shock lamellae,
      • impact, not volcanic
    • Presence of both at Ir anomaly layer strongly supports impact over volcanic origin of Ir
  • Where was the crater?
    • North American marine site suggested
    • distribution of microtektite strewn fields
    • greater abundance and larger grain size of shocked minerals in North American
  • Crater appears to be underwater, just off the Yucatan peninsula
  • Current view
    • Impact of a large object (> 10k) at K/T boundary
    • Threw up very large dust cloud which remained for weeks
    • Impact(s) may have triggered rounds of volcanic eruptions
  • Earth is at risk of future impacts
    • 1/300,000 in our lifetime.
    • earth-crossing asteroids, comets

    • Shoemaker-Levy 9
      • periodic comet that struck Jupiter in a series of impacts last July

    Part two of our tale: Raup and Sepkoski

    • Back to Raup and Sepkoski
      • Looked at extinction rates using families of marine invertebrates
      • found an apparently periodicity of 26 MY for increased extinction rates

    • True periodicity?
      • Still unclear is this periodicity is real as statistical issues in showing true periodicity
    • If true periodicity, what is the cause?
      • too long for most natural cycles,
    • too short for others
    • rotations around the galaxy (200 MY)
  • The teaser
    • Strong Iridium anomalies also seen at
    • Devonian/Carboniferous boundary
    • Permian/Triassic boundary
    • Ordovician/Silurian boundary
    • K/T boundary
  • Impact theory
    • Cratering rates on earth show weak evidence of similar periodicity
    • Extra-terrestrial impacts cause of most/all mass extinctions?
  • The Nemeis (Death Star) model
    • Sun has a small dark companion star
    • when it moves close to the Oort cloud, causes a cometary shower to be sent into the inner solar system

About homelessholocaust

Tijuana Hobo , Hebrew Hobo Railroad Rabbi, The Truth Teller Tell True Truth Truthfully. If the Truth is Repugnant to you, You are a Reagan Cultist. Ronald Reagan was Taught by L. Ron Hubbard, Reagan & Hubbard FOUNDED THE SCIENCE FICTION MIND FUCKING GAME- SCIENTOLOGY- then REAGAN USED NERO LINGUIST PROGRAMMING as PRESIDENT to MURDER THE MINDS of AMERICANS!
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