1. Fossils Fossils are the remains, impression, or other evidence preserved in rock of the existence of life Fossils can be preserved as: –Molds –Casts –Original Bone or mineralized bone –Trace Fossils

2. Molds Formed when the original shell parts of an organism within a sedimentary rock are weathered and eroded leaving a hollowed- out impression.

3. Casts A cast is created once a mold is filled in with minerals or sediment.

4. Original Bone and Shell Original Preservation is the preservation of the soft and hard parts of plant and animals remains that have not undergone any kind of change since the organism’s death.

5. Altered Hard Parts Fossils Altered hard parts of a fossil means that the original parts of the fossil have been replaced with minerals or crystals. The fossil may look like the original bone but upon further examination, one realizes the bone has been replaced.

6. Trace Fossils Fossilized evidence of the behavior of past life such as footprints, nests, burrows, eggs, and droppings. Trace fossils are very important because they give us clues about the lifestyle and behavior of the animal.

7. Virginia Fossils In Virginia, fossils are found mainly in the Coastal Plain (fossils of clams, scallops, sharks teeth), Valley and Ridge (fossils of algae), and the Appalachian Plateau (fossils of plants). –Most Virginia fossils are marine organisms. This indicates that large areas of the state have been under water. –Paleozoic, Mesozoic, and Cenozoic fossils are found in Virginia.

8. Virginia’s Official Fossil Virginia’s official fossil is the Chesapecten jeffersonius:

9. GEOLOGIC HISTORY THE RULES OF THE GAME © Copyright 2005 - 2006 M. J. Krech. All rights reserved.

10. Time is… Either relative or absolute Time is: a measured period during which an event, process, or condition exists or continues.

11. One Year = the time it takes the Earth to complete one orbit around the Sun.

12. Geologic Time Based on the same time units Generally much greater periods of time 100,000 years 1,000,000 years

13. Dating Techniques One ways in which geologists look at time: Relative Dating

14. Relative Dating is.. …the measure of a sequence of events without knowing the exact date at which the events occurred. What happened first? What happened next?

15. Principles of Relative Dating Principle of Superposition Principle of Cross-Cutting Principle of Inclusions Principle of Unconformities

16. Principle of Superposition The youngest rocks are on the top. The oldest rocks are on the bottom.

17. Principle of Superposition Which rocks are older? Which rocks are younger? Q#1

18. Principle of Cross-Cutting Any feature that cuts across another rock or structure is younger than what it cuts across. You can't cut something until that something exists, therefore the cut has to be younger. Volcanic vents cutting across sedimentary rock layers - Which is youngest?

19. Principle of Cross-Cutting What is younger? The rocks or the fault line? Q#2

20. Principle of Inclusions Rock layers which contain other rocks are younger than the inclusion. The inclusion (the other rocks) is older!

21. Principle of Inclusions Which is older? The rock layer or the rocks included in the layer? Q#3

22. Principle of Unconformities Unconformities are surfaces that represent gaps in the geologic record.

23. Principle of Unconformities missing rock layer = missing time

24. Where's the missing sediment? Q#4 How do you know?

25. Where's the missing sediment? Q#5 How do you know?

26. What happened first? Q#6 How do you know?

27. Where is the youngest rock? Q#7 How do you know?

28. Where is the unconformity? Q#8 How do you know?

29. What rock layer is the oldest? Q#9 How do you know?

30. Which is younger? The fault or the rock layers? Q#10 How do you know?

31. Does this diagram show an unconformity? Q#11 How do you know?

32. Which is younger? The rock layer or the inclusion? Q#12 How do you know?

33. The End What do you see here? BONUS: