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Across 1. _________ are large groupings of stars in space; these groupings of stars are classified by shape (Fact 75) 3. The largest _____ ______ in the history of life on Earth occurred at the end of the Paleozoic Era most likely due to climate changes (Fact 92) 5. The three types of rock are igneous, sedimentary, and _________ rock. (Fact 102) 7. A ________ is a naturally formed inorganic solid with a crystalline structure (Fact 100) 11. _______ is a solid mixture of one or more minerals; it is broken down by erosion via wind, water, and ice (Fact 101) 12. ________ rock forms from the transformation of existing rock layers due to heat or pressure (Fact 107) 13. the ______ _______ formed about 4.6 billion years ago from a huge cloud of dust and gas called the solar nebula (Fact 26) 14. The four outer planets or gas giants are _______, Saturn, Uranus, and Neptune (Fact 56) 17. Earth supports life due to the presence of ______ on its surface and in its atmosphere (Fact 50) 18. All of the inner planets are _______, dense and have rocky surfaces (Fact 34) 19. Common organisms that lived during the _________ Era were fish, shellfish, insects, amphibians and reptiles (Fact 91) 20. The four inner or _______ planets are Mercury, Venus, Earth and Mars (Fact 33) 21. Mars may have once had liquid water on its surface but now there are just ___ ____ (Fact 55)

Down 1. The ______ ______ ______ is the "calendar" for events in Earth's history (Fact 85) 2. sedimentary rock forms in layers called ___________ (Fact 106) 4. The _____ ______ is the process in which one rock type changes into another (Fact 103) 6. The sun is a medium sized star made mostly of the elements,________ and helium (Fact 8. ________ rcok forms when lava or pyroclastic material cools and solidifies (Fact 104) 9. During _________ Time, there was plentiful volcanic activity, the atmosphere and the ocean formed and multicellular organisms appeared (Fact 88) 10. All of the gas giants have_____ made of small particles of rocks and ice and have many moons (Fact 58) 13. ________ rock forms when sediments (small pieces of material) are compacted and cemented together or when rocks crystallize out of oceans and lakes (Fact 105) 15. the _______ Era is known as the Age of Mammals because mammals were able to grow, diversify, and occupy both terrestrial and aquatic niches (Fact 98) 16. the _______ Era is known as the Age of the Dinosaurs as they were the dominant life forms. Other organisms that flourished were insects, early mammals, flowering plants and early birds. (Fact 94)