Geologic Time Vocabulary

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Across
  1. 2. The number of years since the rock formed.
  2. 4. The age of a rock compared to the age of other rocks.
  3. 5. An igneous rock layer formed when magma pushes into rock, then cools and hardens.
  4. 6. The preserved remains or traces of living things.
  5. 8. A record of the life forms and geologic events in Earth's history.
  6. 12. In horizontal sedimentary rock layers, the oldest layer is on the bottom. Each higher layer is younger than the layers below it.
  7. 13. An igneous rock layer formed when lava hardens on the surface.
  8. 14. method for studying climate change by drilling cores in ice caps and glaciers that have build up over thousands of years
  9. 15. process by which elements break down by releasing particles and energy
  10. 16. The surface where new rock layers meet the older rock surface beneath them, creating a gap in the geologic record.
  11. 18. Unusual largeness in size or extent.
  12. 19. 4.6 billion years
Down
  1. 1. Scientists who study fossils.
  2. 3. This principal states that the same processes that operate today operated in the past.
  3. 6. Provides evidence about the history of life and past environments on Earth.
  4. 7. The solid layer of rock beneath the soil.
  5. 9. the amount of time it takes for half of its atoms to decay
  6. 10. Scientists use this to test rocks to measure how much radioactive decay has happened. The more decay that has happened, the older the rock is.
  7. 11. A graphic representation of the layers of rock that make up the earth's crust.
  8. 17. fossil A fossil that is widely distributed and represents a type of organism that existed only briefly.