Unit 5: Geologic Time & VA Geology

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Across
  1. 3. the largest division of geologic time
  2. 4. The geologic law/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.
  3. 8. any method of determining whether an event or object is older or younger than other events or objects
  4. 10. Hardened tree sap, yellow to brown in color, often a source of insect fossils
  5. 12. the largest physiographic province in Virginia; between the Fall line and the mountains of the Blue Ridge
  6. 15. any method of measuring the age of an event or object in years using radioactive isotopes
  7. 16. Virginia province which lies to the West of the Valley and Ridge; source of Virginia's most valuable mineral resource
  8. 18. A trace of an ancient organism that has been preserved in rock.
  9. 20. An igneous rock layer formed when magma hardens beneath Earth's surface
  10. 21. A fossil created by an impression.
  11. 24. long parallel ridges to the west of the Blue Ridge mountains which are part of the major landform feature of North America; a region of karst topography
  12. 25. fossils of widely distributed organisms that lived during only one short period
  13. 28. The impression of an organism in a rock (hollow)
  14. 29. "Law of..." in a sequence of sedimentary rocks, layers of rock were originally formed lying horizontally
  15. 30. Age of reptiles
  16. 31. Any piece of rock (clast) has become incorporated into another rock, this clast must be older than rock matrix it is included in it
  17. 32. the tallest mountains in Virginia; folded and faulted igneous rock formed when African and North America collided
  18. 33. the time it takes 50% of radioactive isotopes to decay to stable
Down
  1. 1. era that began about 66 million years ago, known as the "Age of Mammals"
  2. 2. A description of plants or animals that have been preserved by being "turned to stone"
  3. 5. the division between the Piedmont and the Coastal Plain, where various rivers cross from hard bedrock to soft sediments; marked by a line of rapids and waterfalls
  4. 6. A trail, nest, burrow, or evidence of organism found fossilization in sediments; it shows the activity of an organism, but is not made of the organism itself.
  5. 7. "Law of..." An inclusion must be older than the rock it is enclosed in
  6. 9. a crack in the earth's crust resulting from the displacement of one side with respect to the other
  7. 11. the youngest province in Virginia; from the Fall Line eastward to the Atlantic Ocean; a broad, flat area of unconsolidated sediments along the coastline
  8. 13. Virginia's most valuable mineral resource
  9. 14. the part of geologic time 570-245 million years ago ; invertebrates, fishes, amphibians, reptiles, ferns, and cone-bearing trees were dominant
  10. 17. a fossil copy of an organism in a rock (filled)
  11. 19. formed when layers of sediment such as clay, mud, silt, or sand hardened over million years. These types of sediments are laid down in lakes, swamps and oceans.
  12. 22. A scientist who studies the forms of life that existed in former geologic periods, mainly by studying fossils.
  13. 23. A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
  14. 26. no longer in existence
  15. 27. makes up about 88 % of earth's history; when the oceans, atmosphere, and continents were formed