Chapter 3 7th Grade The Rock and Fossil Record

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Chapter 3 7th Grade The Rock and Fossil Record

• Section 1- Earths 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 suddenlyrapid
  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

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• Section 2Relative Dating Which Came First
• 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 Columnarrangement of rock layers
  in which oldest are at the bottom.

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• 3. Disturbed Rock Layer
• a. Fault-break in the earths crust where blocks
  of crust slide relative to each other
• b. Intrusion- molten rock from the interior
  squeezes into existing rock and cools.
• c. Foldingwhen 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

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• Section 3Absolute 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 decay

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Section 4Looking 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 organisms tissue
• Permineralization-the pore space (bone or wood)
  is replaced by minerals

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• 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

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• 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.

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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

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• The Appearance and Disappearance of Species
• Extinction-no longer living all of that species
  are dead
• The Paleozoic Era-Old Life
• The Mesozoic Era-The Age of Reptiles
• The Cenozoic Era- The Age of Mammals