A Trip Through Geologic Time

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Across
  1. 2. film A type of fossil consisting of an extremely thin coating of carbon on rock
  2. 4. A type of fossil that is a hollow area in sediment in the shape of an organism or part of an organism
  3. 5. One of the three units of geologic time in which geologists divide eras
  4. 6. fossil A fossil in which minerals replace all or part of an organism
  5. 9. A fossil that is a solid copy of an organism's shape formed when minerals seep into the mold
  6. 10. A vertebrate whose body temperature is regulated by its internal heat, and has skin covered with hair or fur and glands that produce milk to feed its young
  7. 11. A break in Earth's crust along which rocks move
  8. 12. A vertebrate whose body temperature is determined by the temperature of its environment, and lives its early life in water and its adult life on land
  9. 16. Fossils of widely distributed organisms that lived through a geologically short period
  10. 18. A loose connection of ice and dust that orbits the sun, typically a very narrow orbit
  11. 19. A vertebrate whose body temperature is determined by the temperature of its environment, that has lungs and has scaly skin, and lays eggs on land
  12. 20. A gap in the geologic record that shows where rock layers have been lost due to erosion
  13. 21. The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it
  14. 23. The process in which the nuclei of radioactive elements break down, releasing fast moving particles and energy
  15. 25. Term used to refer to a group that have died out and no longer have any living members
  16. 26. The age of rock given as the number of years since the rock formed
  17. 27. Change over time; the process by which modern organisms have descended from ancient organisms
  18. 29. extinction When many types of living things become extinct at the same time
Down
  1. 1. One of the three long units of geologic time between the Precambrian and the present
  2. 3. age The age of rock compared to the ages of other rocks
  3. 7. An igneous rock layer formed when lava flows onto Earth's surface and hardens
  4. 8. The time it takes for half of the atoms of radioactive elements to decay
  5. 13. A scientist who studies fossils to learn about organisms that lived long ago
  6. 14. An animal with a backbone
  7. 15. The preserved remains or traces of an organism that lived in the past
  8. 17. A record of the geologic events and life forms in Earth's history
  9. 22. An animal without a backbone
  10. 24. An igneous rock layer formed when magma hardens beneath Earth's surface
  11. 28. fossil A type of fossil that provides evidence of activities of an ancient organism