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Across 3. is a ball of dust and ice thats orbits the sun 5. the surface where new rock layer meet a much older rock surface beneath them 9. is an animal that lives part of its life on land and part of its life in water 16. geologists divide the time between Precambrain Time and the present into three long units of time 17. is a well-tested concept that explain a wide range of observations 19. provide evidence of the activties of ancient organisms. 23. is a record of the life forms and geologic events in Earth history. 27. are fossil in which minerals replace all or part of an organism 28. is a warm-blooded vertebrate that feeds its young milk 29. lava that hardens on surface 30. is an animal with a backbone

Down 1. is the gradual change in living things over long periods of time 2. a fossil must be widely distributed and represent a type of organism that existed only briefly 4. if it no longer exists and will never again live on earth. 6. in which man types of living things became extint at the same time 7. the magma cools and hardens into a mass of igneous rock 8. without a backbone 10. is its compared to the ages of other rocks 11. an extremely thin coating of carbonon rock 12. to determine the relative ages of sedimentary rocks layers 13. is the type of rock that is made of hardened sediment 14. use fossils to build up picture of earth's past environments 15. a rock is the number of years since the rock formed 18. continents move very slowly over earth's because of force inside earth. 20. eras are subdivided into units of geologic time 21. have scaly skin and lay eggs with tough, leathery shell 22. are the preserved remain or traces of living things 24. is a soild copy of the shape of an organim 25. is a hallow area in sediment in the shape of an organism or part of an organism 26. is a break in Earth's crust