History

• What is the estimated age of the Earth?

  About 4.6 billion years
• How did scientists determine the age of the Earth?

  Using radiometric dating methods
• What was the early state of the Earth described as?

  A magma ocean
• What caused the heat in the early Earth?

  High-speed collisions of space rocks
• What happened as the collisions of space rocks tapered off?

  The Earth began to cool and form a crust
• What occurred as water vapor escaped in the early atmosphere?

  Clouds formed and storms raged
• What did the storms on primitive Earth lead to?

  Flooding the surface and forming seas
• What are fossils?

  Preserved remains or traces of organisms
• How is the age of a fossil determined?

  By the age of the rock it is found in
• What is fossilization?

  The process of fossilizing ancient organisms
• What are the two main types of fossils?

  1. Body fossils
  2. Trace fossils
• What are body fossils?

  Parts of an organism like bones and shells
• What are trace fossils?

  Evidence of life like burrows and tracks
• What are the types of trace fossils?

  1. Tracks
  2. Burrows
  3. Coprolites
  4. Gastroliths
• What are tracks in the context of trace fossils?

  Animal footprints in soft sediments
• What are burrows in trace fossils?

  Holes made by animals filled with minerals
• What are coprolites?

  Fossils of stomach contents of animals
• What are gastroliths?

  Stones found in the stomach of reptiles
• What are the modes of fossil preservation?

  1. Unaltered

  • Preservation without change
  • Examples: entombments, mummification, refrigeration

  1. Altered

  • Preservation with changes
  • Examples: permineralization, replacement, carbon film
• What is the longest subdivision of geologic time?

  Eons
• What marks the end of an era in the geologic time scale?

  Major changes in the fossil record
• What are periods based on in the geologic time scale?

  Types of life existing at the time
• What characterizes epochs in the geologic time scale?

  Differences in life forms across continents
• What characterized the Archean Era's atmosphere?

  Contained methane with little oxygen
• What was a significant feature of the Archean Era?

  Most of Earth was covered with water
• What type of fossils were formed during the Paleozoic Era?

  Marine invertebrates in shallow water
• What significant development occurred in the Devonian Period?

  Amphibians began to breathe air
• What type of plants began to develop in the Devonian Period?

  Giant ferns and marsh plants
• What major geological activity occurred during the Cenozoic Era?

  Mountains were uplifted
• What type of animals roamed the land during the Cenozoic Era?

  Warm-blooded animals like kangaroos
• What evidence of humans was found during the Cenozoic Era?

  Stone tools used by humans