Chapter 3 7th Grade The Rock and Fossil Record

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					           Chapter 3
 7th Grade The Rock and Fossil

 Section 1- Earth’s Story and Those Who First Listened
           1. The Principle of Uniformitarianism
a. Processes that we observe today-such as erosion and
    deposition do not change over time-still going on.
   b. Catastrophism- is the principle that states that all
    geologic changes occur suddenly—rapid changes
           2. Modern Geology- A Happy Medium
a. States that both uniformitarianism and catastrophism
                both helped form the earth.
    3. Paleontology- study of the past life on the earth
• Section 2—Relative Dating: Which Came
• Relative Dating- determining if an object is
  older or younger than other objects.
• 1. The Principle of Superposition
• a. The principle states younger rocks lie
  above older rocks.
• b. Disturbing Forces
• a. Forces change this by tilting, folding and
  breaking into movable forces.
• 2. The Geologic Column—arrangement of
  rock layers in which oldest are at the bottom.
•   3. Disturbed Rock Layer
•   a. Fault-break in the earth’s crust where blocks of crust slide relative
    to each other
•   b. Intrusion- molten rock from the interior squeezes into existing rock
    and cools.
•   c. Folding—when layers bend and buckle.
•   d. Tilting-internal forces in the Earth slant rock layers.

•   4. Gaps in the Record-Unconformities
•   a. Layers of rock missing completely
•   b. Missing evidence- Unconformity is a surface that represents a
    missing part in the geologic column.
•   i. Nondeposition- stoppage of deposition when sediment is cut off

•   5. Types of Unconformities
•   a. Disconformities
• Section 3—Absolute Dating: A Measure of Time
• Absolute Dating- telling the age of an object by determining
  how long it has existed.
• 1. Radioactive Decay
• a. Isotopes- an element with the same number of protons, but a

• different number of electrons.
• b. Most are stable, meaning they stay in their normal form.
  Some are unstable.
• c. Unstable isotopes are called radioactive
• 1. Parent isotope- unstable
• 2. Daughter isotope- stable isotope produced by the decay of
  the parent isotope.

• 2. Radiometric Dating
• a. based on the ratio of parent material to the daughter material
• b. half-life is the time it takes one half of a radioactive sample to
                 Section 4
             Looking at Fossils
• Fossilized Organisms
  – Fossil-remains or physical evidence of an organism
• Fossils in Rocks
  – Hard parts of animals- shells & bones
• Fossils in Amber
  – Amber-hardened tree sap
• Petrification
  – Minerals replace an organism’s tissue
  – Permineralization-the pore space (bone or wood) is
    replaced by minerals
  – Fossils in Asphalt
     • LaBrea asphalt pits
  – Frozen Fossils
     • Preserved from the last ice age
• Other Types of Fossils
  – Trace Fossils
     • Naturally preserved evidence of animal activity
  – Molds and Casts
     • Mold –cavity where the animal is buried
     • Cast-an object created when sediment fills in a mold.
• Using Fossils to Interpret the Past
  – The information in the Fossil Record
     • Rough sketch of the history of life on earth
• History of Environmental Change
  – Marine fossils on a mountain top
  – History of Changing Organisms
     • Only a small portion of animals have been fossilized
• Using Fossils to Date Rocks--Index Fossils are
  fossils of organisms that lived in a very short
  well defined geologic time span
  – Ammontes called Tropites index fossil of 230-208
    million years ago.
  – Trilobites called Phacops 400 million years ago.
               Section 5
            Time Marches On
• Geologic Time
  – The Rock Record and Geologic Time
  – The Fossil Record and Geologic Time
• The Geologic Time Scale
  – Divisions of Time
    •   Eons-largest- 4 of these
    •   Eras-second largest- 3 of them
    •   Periods-third largest
    •   Epochs-fourth largest
– The Appearance and Disappearance of
  • Extinction-no longer living – all of that species are
– The Paleozoic Era-Old Life
– The Mesozoic Era-The Age of Reptiles
– The Cenozoic Era- The Age of Mammals

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