A Trip Through Geologic Time

123456789101112131415161718192021222324252627
Across
  1. 1. One of the three long units of geologic time between the Precambrian and the present
  2. 3. film A type of fossil consisting of an extremely thin coating of carbon on rock
  3. 5. An igneous rock layer formed when magma hardens beneath Earth's surface
  4. 9. 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
  5. 11. An animal with a backbone
  6. 12. A gap in the geologic record that shows were rock layers have been lost due to erosion
  7. 13. A loose connection of ice and dust that orbits the sun, typically a very narrow orbit
  8. 14. The age of rock compared to the ages of other rocks
  9. 19. The process in which the nuclei of radioactive elements break down, releasing fast moving particles and energy
  10. 21. One of the three units of geologic time in which geologists divide eras
  11. 22. fossil A fossil in which minerals replace all or part of an organism
  12. 23. An animal without a backbone
  13. 24. 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
  14. 27. A scientist who studies fossils to learn about organisms that lived long ago
Down
  1. 1. Change over time; the process by which modern organisms have descended from ancient organisms
  2. 2. The preserved remains or traces of an organism that lived in the past
  3. 4. The age of rock given as the number of years since the rock formed
  4. 6. Term used to refer to a group that have died out and no longer have any living members
  5. 7. 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
  6. 8. A record of the geologic events and life forms in Earth's history
  7. 10. 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
  8. 13. A fossil that is a solid copy of an organism's shape formed when minerals seep into the mold
  9. 15. fossil A type of fossil that provides evidence of activities of an ancient organism
  10. 16. The time it takes for half of the atoms of radioactive elements to decay
  11. 17. A break in Earth's crust along which rocks move
  12. 18. Fossils of widely distributed organisms that lived through a geologically short period
  13. 20. An igneous rock layer formed when lava flows onto Earth's surface and hardens
  14. 25. extinction When many types of living things become extinct at the same time
  15. 26. A type of fossil that is a hollow area in sediment in the shape of an organism or part of an organism