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