Across
- 1. No longer in existence
- 2. Lasted from 1200 to 1000 million years ago
- 3. Approximately the last 63 million years
- 4. Lasted from 1600 to 1400 million years ago
- 7. From 190 million to 135 million years ago
- 8. From 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian (to 430.5 million years ago) and Homerian ages
- 10. A fossil formed when an animal, plant, or other organism dies and is covered by sediment
- 11. Lasted from 850 to 635 million years ago
- 12. From 13 million to 2 million years ago; growth of mountains; cooling of climate; more and larger mammals
- 16. From 542 to ~510 million years ago; first appearance of trilobites
- 17. Hard translucent fossilized resin
- 18. starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago
- 21. From 271 to 260 million years ago; rock strata and fossils were formed
- 22. The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms
- 24. began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago
- 28. From 310 million to 280 million years ago
- 32. From 135 million to 63 million years ago
- 35. lasted from 1800 to 1600 million years ago; supercontinent Columbia formed
- 37. From 423 ± 1.5 to 419.2 ± 2.8 mya, is the final and shortest epoch of the Silurian
- 39. Lasted from 1400 to 1200 million years ago
- 41. Lasted from 2050 to 1800 million years ago; large asteroid collision created the Vredefort impact structure
- 43. From 544 million to about 500 million years ago; marine invertebrates
- 44. The last 10000 years
- 46. From 405 million to 345 million years ago
Down
- 1. From 560 and 545 million years ago
- 4. From about 299 to 270 million years ago; marked by the appearance of beetles and flies
- 5. From 63 million to 58 million years ago; appearance of birds and earliest mammals
- 6. From about 501 to 488 million years ago; marked by an "explosion" of life
- 9. Lasting from roughly 358.9 ± 0.4 to 323.2 ± 0.4 million years ago
- 10. From 25 million to 13 million years ago; appearance of grazing mammals
- 13. From 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds
- 14. From 40 million to 25 million years ago; appearance of sabertoothed cat
- 15. A process of fossilization by gradual substitution of mineral matter for the original organic matter Also called petrification
- 16. From 230 million to 190 million years ago
- 19. From 230 million to 63 million years ago
- 20. The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock
- 23. Lasted from 2 million to 11000 years ago; the time of human evolution
- 25. From 58 million to 40 million years ago; presence of modern mammals
- 26. Last 2 million years
- 27. From 280 million to 230 million years ago
- 29. From 544 million to about 230 million years ago
- 30. The process by which organic material is converted into stone through the replacement of the original material and the filling of the original pore spaces with minerals
- 31. Lasted from 2500 to 2300 million years ago; the oxygen catastrophe
- 33. From 425 million to 405 million years ago
- 34. From about 260 to 251 million years ago; marked by the formation of the Pangea supercontinent
- 36. From 443.4 ± 1.5 to 433.4 ± 2.8 mya, and is subdivided into three stages: the Rhuddanian,[8] lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, and the Telychian
- 38. A fossil formed when an animal, plant, or other organism dies, its flesh decays and bones deteriorate due to chemical reactions; minerals gradually enter into the cavity
- 40. Lasted from 2300 to 2050 million years ago; global glaciation began
- 42. Lasted from 1000 to 850 million years ago
- 45. Lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago