Fossils and the Rock Record by Annie Cloutier  Sandwich High School 2011  copyright Chapter 21 Earth & Space Science GTS
How can we measure time ? <ul><ul><ul><ul><ul><li>Imagine…. </li></ul></ul></ul></ul></ul><ul><li>no clocks </li></ul><ul>...
Earth’s History is Measured in GTS Geologic Time Scale <ul><li>Eon  –  longest time unit measured in billions of years * T...
MYBP <ul><li>MYBP = millions of years before present </li></ul><ul><li>BYBP = billions of years before present </li></ul><...
<ul><li>LIFE </li></ul>
Percent of Time 90% of Earth’s GTS was in the PrecambrianTime 6 % Paleozoic 4% Mesozoic 1% Cenozoic
paleo means “ancient” zoic means “life” Paleozoic means “ancient life” <ul><li>Meso means “ middle” </li></ul><ul><li>Ceno...
Relative Dating is   not going  to a movie with Grandma…
Relative dating  of rocks is  what James Hutton’s   hypothesized in 1770 …theory of   Uniformitarian' s -  states that the...
Rocks  are never left alone. <ul><li>Superpositioning  states that in an undisturbed rock sequence the oldest rocks are on...
Original horizontality is the natural layering of sedimentary rocks deposited in a horizontal or nearly horizontal layer. ...
Exceptions to the rule <ul><li>Sometimes lava or magma in volcanic dikes or sills, intrude in a rock formations, in  cross...
Unconformity   is when an erosion surface might become buried by the deposition of younger rocks.   Disconformity  is when...
Absolute Age of Rocks  STOP  let me see you license I don’t believe how old you are <ul><li>Scientist can actually date th...
Uranium 238  converts into  Lead 206
CSI  crime scene investigation   uses  Carbon  <ul><li>Carbon has a half life of 5730 years.  </li></ul><ul><li>Decay prod...
Time  is relative to the life forms existing and to the significant objects in the Universe. <ul><li>People in their 40’s ...
The end of measuring the passing of time time machine   time machine
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Fossils and the Rock Record acloutier copyright 2011 February

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Geologic Time Relative Dating Absolute Age of Earth "s Rocks

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Fossils and the Rock Record acloutier copyright 2011 February

  1. 1. Fossils and the Rock Record by Annie Cloutier Sandwich High School 2011 copyright Chapter 21 Earth & Space Science GTS
  2. 2. How can we measure time ? <ul><ul><ul><ul><ul><li>Imagine…. </li></ul></ul></ul></ul></ul><ul><li>no clocks </li></ul><ul><li>no books </li></ul><ul><li>no TV </li></ul><ul><li>no radio </li></ul><ul><li>no Internet </li></ul><ul><li>no cell phones </li></ul>
  3. 3. Earth’s History is Measured in GTS Geologic Time Scale <ul><li>Eon – longest time unit measured in billions of years * The longest Era known is the ARCHEAN EON 4,600 billion years before present </li></ul><ul><li>Era – next longest span of time measured in hundreds of millions to billions of years </li></ul><ul><li>Period – are defined by the life forms that were abundant or became extinct during the time in which specific rocks were deposited –tens of millions tohundreds of million years </li></ul><ul><li>Epoch – Shortest unit of time from millions to tens of millions of years </li></ul>
  4. 4. MYBP <ul><li>MYBP = millions of years before present </li></ul><ul><li>BYBP = billions of years before present </li></ul><ul><li>Today we live in the . . . </li></ul><ul><li>Recent Epoch </li></ul><ul><li>In the Quaternary Period </li></ul><ul><li>Cenozoic Era - 1.6 MYBP to present day </li></ul><ul><li>Within the Phanerozoic Eon </li></ul>
  5. 5. <ul><li>LIFE </li></ul>
  6. 6. Percent of Time 90% of Earth’s GTS was in the PrecambrianTime 6 % Paleozoic 4% Mesozoic 1% Cenozoic
  7. 7. paleo means “ancient” zoic means “life” Paleozoic means “ancient life” <ul><li>Meso means “ middle” </li></ul><ul><li>Ceno means “recent” </li></ul>
  8. 8. Relative Dating is not going to a movie with Grandma…
  9. 9. Relative dating of rocks is what James Hutton’s hypothesized in 1770 …theory of Uniformitarian' s - states that the processes occurring today have always been occurring since Earth was formed. <ul><li>this is not an exact science of dating rocks, more like an estimate of time with no exact dates “sort of a ball park figure” </li></ul>
  10. 10. Rocks are never left alone. <ul><li>Superpositioning states that in an undisturbed rock sequence the oldest rocks are on the bottom. Before we do the laundry, the oldest dirty clothes are on the bottom of the basket. </li></ul>
  11. 11. Original horizontality is the natural layering of sedimentary rocks deposited in a horizontal or nearly horizontal layer. <ul><li>Think of the Grand Canyon the oldest rocks are at the bottom layer of the canyon. </li></ul><ul><li>Vishnu Group rocks at the very bottom are from the Precambrian </li></ul>
  12. 12. Exceptions to the rule <ul><li>Sometimes lava or magma in volcanic dikes or sills, intrude in a rock formations, in cross-cutting this can be the case so an intrusion is younger than the original rock. </li></ul>
  13. 13. Unconformity is when an erosion surface might become buried by the deposition of younger rocks. Disconformity is when horizontal sedimentary rocks overlay other horizontal sedimentary rocks <ul><li>James Huttons illustration of rock layers </li></ul>
  14. 14. Absolute Age of Rocks STOP let me see you license I don’t believe how old you are <ul><li>Scientist can actually date the true age of many rocks and fossils. This is called Absolute –Age. </li></ul><ul><li>By measuring the decay rates of radioactive isotopes. </li></ul><ul><li>Isotopes are found in igneous and metamorphic rocks, some fossils and , organic remains (once living) </li></ul><ul><li>Radioactive substances emit nuclear particles at a constant rate, the protons and neutrons change with each nuclear emission </li></ul><ul><li>As the number of protons and neutrons change with each nuclear emission, the element changes by converting into a different element. </li></ul><ul><li>The original element is the “parent” </li></ul><ul><li>The new element is the “daughter” </li></ul>
  15. 15. Uranium 238 converts into Lead 206
  16. 16. CSI crime scene investigation uses Carbon <ul><li>Carbon has a half life of 5730 years. </li></ul><ul><li>Decay product Nitrogen -14 </li></ul><ul><li>Uranium 238 has a half life of 4,5 billion years </li></ul><ul><li>Decay product Lead 206 </li></ul><ul><li>“ if it wasn’t for Carbon 14, I would not date at all.” </li></ul>
  17. 17. Time is relative to the life forms existing and to the significant objects in the Universe. <ul><li>People in their 40’s are at the half way point in life </li></ul><ul><li>The Sun is at the estimated half way point in it’s life…3.5 billion years old </li></ul>
  18. 18. The end of measuring the passing of time time machine time machine

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