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

I actually do not write most of these articles, I collect them here, for my personal useage, I find Some Other's enjoy them as well, which is a side effect of my Senility. As I am a Theosophist, and also study Vedanta Society of Northern California, so Your Visitation from the Akashic records to approve my feebile works gives me Great Hope! I am 68, years old, I will Come To You in another 30 or so years. You Reinforces my Belief that in my Sleep I visit The Akashic Records when I remember my dream's. I keep notes about 'Over There." the Colour of Daylight is Darker, but the Life is Brighter, property has no meaning, and it is homish. are the energetic records of all souls about their past lives, the present lives, and possible future lives. Each soul has its Akashic Records, like a series of books with each book representing one lifetime. The Hall (or Library) of the Akashic Records is where all souls’ Akashic Records are stored energetically. In other words, the information is stored in the Akashic field (also called zero point field). The Akashic Records, however, are not a dry compilation of events. They also contain our collective wisdom.
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