Fossils

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Fossils Geologic Time

• Mrs. Wisher

WRITE EVERYTHING IN YELLOW!!
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What Are Fossils?

• Fossils are formed when living things die and are
  trapped in sediments and become rocks
• Petrified fossils are where minerals replace all
  or part of an organism
• Trace fossils provide evidence of the activities
  of organisms

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Dating Fossils

• Relative age dating compares their age to age
  of other rocks
• Absolute age dating tells their age in years by
  looking at the decay of isotopes

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Relative Dating
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Preserved Remains

• Real parts of real organisms that have not
  changed
• Wooly Mammoth in ice or tar
• Insects in amber
• Mummified remains

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Preserved Remains

• Long before white men came, Indians knew of and
  worked in Mammoth Cave in KY. In 1935 two guides
  exploring found a mummy high on a ledge. From its
  position and the articles found with it,
  archeologists pieced together the story. An
  Indian miner was digging for something in sand on
  the ledge. A rock above slipped and pinned him
  down. The body, found many centuries later in an
  excellent state of preservation, was clad in a
  breech clout, woven of fiber. Crude stone
  implements lay nearby.. Close by bundles of
  reeds, thrust into the sand with singed ends
  indicated he was using them as a torch. The mummy
  was found three miles from the nearest natural
  entrancethree miles of pitch black darkness,
  lighted for that long-ago miner only by the reed
  torches he carried. Today the mummy rests in an
  air-tight glass case just below the ledge on
  which it was found.

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QUESTIONS

• Students at B seats close your notebook and
  teach your table the difference between relative
  and absolute dating.

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QUESTIONS

• Students at B seats close your notebook and
  teach your table the difference between relative
  and absolute dating.
• Relative dating is using the position of the rock
  layers to determine which is youngest or oldest.
  Absolute dating gives you a time frame of age
  based on radioactive decay.

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Molds Casts

• Mold an impression of the organism

• Cast an object formed when a mold is filled
  with sediment

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Geological Time Scale

• Why use geological time?
• Earth is about 4.6 billion years old
• Modern humans have only been here less than
  100,000 years or less than 1 of Earths history.

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Geologic Time Scale

• Eras geological history is divided into 4 eras
• Periods each era is divided into periods
• What 3 periods make up the Mesozoic era?
• Epochs each period is subdivided into an epoch
• Only the Cenozoic (or most recent) era is divided
  into epochs. Can you think of why?

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Precambrian Era

• Early bacteria and algae form
• First sedimentary rocks appear
• First multicellular organisms develop late in
  Precambrian.

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Phanerozoic Eon visible life

• 1. Paleozoic Era (old life)
• 2. Mesozoic Era (middle life)
• 3. Cenozoic Era (recent life)

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Paleozoic Era

• 570 mya to 225 mya
• Trilobites were common animals
• Life explodes during the Paleozoic
• Land plants appeared in middle Paleozoic.
• Age of the Fish, all animal life is in the sea
  - sharks, rays, and bony fish existed.

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Paleozoic Era

• Tropical jungle like forest were prevalent by the
  end of the era.
• Insects (some huge) were the predominant animals.
• Reptiles evolved during the late Carboniferous
  period
• A mass extinction at the end of the Paleozoic
  wiped out 95 of all life

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Mesozoic Era

• 225 mya 65 mya
• Age of the Reptiles
• Dinosaurs roamed Earth.
• Pangaea breaks up during the Jurassic period and
  is in the present position by the late Cretaceous
  period

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Mesozoic Era

• Birds and mammals started evolving during the
  last part of the Mesozoic.
• Widespread volcanic activity occurs
• Mass extinction at the K-T boundary is supported
  by the fossil record

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Cenozoic Era

• Recent Life (65 mya to present)
• Divided into the Tertiary Quaternary period
• Age of mammals
• Ice Age began 3 mya (on New Years Eve.)
• Took 75000 years to form, stayed 10000 years,
  then retreated.

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Cenozoic Era

• Early animals could be much different than their
  modern versions.
• Early horses were much smaller and had toes.

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Questions?

• Discuss with your shoulder partner, why do you
  believe that each of the Eras ended at the time
  frame that they ended.

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Questions?

• Discuss with your shoulder partner, why do you
  believe that each of the Eras ended at the time
  frame that they ended.
• Each of the Eras (except the Cenozoic which we
  are still in) ended with a mass extinction event.

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Age of Man

• Man evolved at 1030 pm on New Years Eve.
• Hominids evolved during the Quaternary period
• Australopithecus, the earliest ancestor, evolved
  around 3 million years ago
• Early hominids include Homo erectus, habilis, and
  neanderthalensis
• Homo Sapian sapian is the modern man

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Homo Neanderthalensis
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Otzi the Iceman
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