The Rock Record

1. The Rock Record read pages 596-609 restate & answer Topic Questions 1-14 Chapter 32 Earth Science Book

2. Topic 1: Page 597 Earth Textbook Telling Time • James Hutton (1726-1797). Proposed that most geologic processes happen very slowly. • Relative Time - Position in that sequence; older or younger than nearby layers • Absolute Time - Numerical Age can be determined through analysis of the products of radioactive decay

3. Layered rocks contain clues about past environments at/near surface. Sequence and relative ages provide basis for reconstructing Earth’s history. The study of strata is called stratigraphy. Topic 1: Page 597 Earth Textbook Stratigraphy

4. The basis of rock stratigraphy is the formation. - a collection of similar strata that are sufficiently different from adjacent groups - basis of physical properties they constitute a distinctive, recognizable unit that can be used for geologic mapping over a wide area. Topic 1: Page 597 Earth Textbook Stratographic Classification

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6. 19th century – geologists assembled a geologic column composite column containing, in chronological order, the succession of known strata, fitted together based of fossils or other evidence of relative age. This is the geologic time scale. Topic 1: Page 597 Earth Textbook Geologic Column & Geologic Timescale

7. Topic 2: Page 597 Earth Textbook Relative Time *Law of Superposition *Law of Cross-cutting Relationships Relative ages: younger or older *Law of Included Fragments *Unconformities

8. Topic 2: Page 597 Earth Textbook Law of Superposition

9. Law of Superposition: Grand Canyon Strata Topic 2: 9

10. Topic 2: Page 597 Earth Textbook Law of Superposition: Sediments Most sediment is laid down in the sea, in shallow waters, or in streams. Each new layer is laid down horizontally over older ones Principle of original horizontality - sediments are deposited in strata that are horizontal or nearly horizontal

11. Topic 2: Page 597 Earth Textbook Law of Superposition: Horizontality 11

12. Topic 2: Page 597 Earth Textbook

13. Topic 2: Page 597 Earth Textbook Law of Cross-Cutting Relationships A fault is a break or crack in Earth’s crust where rocks shift their positions. Law of cross-cutting relationships = a fault or igneous intrusion is always younger than the rock layers it cuts through

14. Topic 2: Page 597 Earth Textbook Law of Cross-Cutting Relationships 14

15. Law of Cross-Cutting Relationships

16. Topic 2: Law of Cross-Cutting Relationships • Based on the law of superposition, what is the oldest layer pictured? Igneous intrusion Fault

17. Topic 2: Law of Cross-Cutting Relationships • Based on the law of superposition, what is the oldest layer pictured? A is the oldest, D is youngest Igneous intrusion Fault

18. Topic 2: Law of Cross-Cutting Relationships • Based on the law of superposition, what is the oldest layer pictured? A is the oldest, D is youngest • Based on the law of crosscutting relationships, which is older, the fault or the igneous intrusion? Igneous intrusion Fault

19. Topic 2: Law of Cross-Cutting Relationships • Based on the law of superposition, what is the oldest layer pictured? A is the oldest, D is youngest • Based on the law of crosscutting relationships, the igneous intrusionis older than the fault? Igneous intrusion Fault

20. List the labeled formations from youngest to oldest.

21. List the labeled formations from youngest to oldest. C B A E D

22. Topic 2: Page 597 Earth Textbook Law of Included Fragments Pieces of one rock found in another rock must be older than the rock in which they are found. “ingredients are older than the rock” included fragments are older than the rock

23. Law of Included Fragments

24. Topic 2: Page 597 Earth Textbook Unconformities Unconformities are breaks in the geologic record that show deposition stopped for a period of time, rock was removed by erosion, and deposition resumed. Angular unconformity

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26. Evidence of former seafloors uplifted by tectonic forces and exposed to erosion. Later tectonic forces depress the surface. The surface, in turn, becomes a site of deposition of sediment. Topic 2: Page 597 Earth Textbook The Significance of Unconformities

27. Topic 3: Page 598 Earth Textbook Geologic Timetable 5 Eras of Earth’s History 1. Archean: 4.5-2.5 Billion Years Ago 2. Proterozoic: 2.5 BYA-570 MYA 3. Paleozoic: 570-250 MYA 4. Mesozioc: 250-65 MYA 5. Cenozoic: 65 MYA- Today summary of major events in Earth’s History *Eras broken into Periods, Periods into Epochs

28. Topic 3: Page 598 Earth Textbook Geologic Time and the Rock Record Chapter 8 Chapter 8

29. The divisions of the geologic time scale. Topic 3:

30. Figure 11.10

32. Topic 3:

33. Topic 3: Scale of the Geologic Time

34. Topic 3:

35. Topic 4: Page 602 Earth Textbook *Any evidence of earlier life preserved in rock Fossil Formation • original remains: unchanged organisms • replaced remains: become calcite, silica • molds, imprints, casts or hollows • trace fossils: trails burrows, footprints

36. Topic 4: Studying The Past What is a Fossil? Definition: The evidence or remains of once-living plants or animals Why Do We Study Fossils Found in Rocks? To provide evidence of the past existence of life forms To provide information about past environmental conditions To provide evidence that populations have undergone change over time due to environmental changes (evolution)

37. Fossil Formation Topic 4: Original Preservation Description: plant or animal remains that have not undergone change since death. • Uncommon because frozen, extremely dry, or oxygen-free environments are required to form these fossils • Examples: • Mummified humans • Frozen organisms (Ice Man) • Mammoths & cats in La Brea Tar Pits • Fossilized insects in tree sap (amber)

38. Fossil Formation Topic 4: Replaced Hard Parts Description: all organic material has been removed and the hard parts of the organism have been changed • Minerals seep in slowly and replace the original organic tissue, forming a rock-like fossil • The fossil has the same shape as the original object, but is chemically more like a rock! • Examples: • Petrified wood • Recrystallized shells

39. Fossil Formation Topic 4: Molds and Casts Description: Fossils that do not contain any shell or bone • A mold is formed when original shell parts are weathered and eroded, leaving an impression of the shell. • This cavity might later become filled with minerals or sediment to create a cast. • Examples: • Common with shellfish

40. Fossil Formation Topic 4: E. Trace Fossils • Description: Indirect evidence of plant and animal life • Provide information about how an organism lived, moved or obtained food • Examples: • worm trails • burrows • footprints

41. How Fossils Are Formed

42. Freezing (refrigeration) Best means of preservation of ancient materials. Rare - continually frozen from death til discovery. Mammoths and wooly rhinoceros found in ice from Alaska and Siberia. Specimens with flesh, skin, and hair intact have been found. suggest that they were flash frozen, with food still in the mouth and stomach. Topic 4:

43. Drying (desiccation) Mummified bodies discovered in arid parts Soft tissues preserved if completely dried. Topic 4: Page 602 Earth Textbook

44. Asphalt La Brea Tar Pits - 100 pits filled with sticky asphalt or tar. formed by crude oil seeping through fissures in the earth. lighter elements evaporated leaving thick sticky asphalt. pits are famous for Pleistocene fossils The fossils date between 10 and 40 thousand years old. Asphalt is an excellent preservative. Topic 4:

45. Amber (Unaltered preservation) Insects, spiders, and even small lizards have been found, nearly perfectly preserved in amber. Over millions of years, sap with our fly inside is polymerized and hardened into amber. Topic 4: Page 602 Earth Textbook

46. Permineralization (Petrification) most common Minerals fill the cellular spaces and crystallize. Shape of the original plant or animal is preserved as rock. Sometimes the original material is dissolved away leaving the form and structure but none of the organic material remains.

47. Carbonization Plant leaves, and some soft body parts of fish, reptiles, and marine invertebrates decompose leaving behind only the carbon. This carbon creates an impression in the rock outlining the fossil, sometimes with great detail. Topic 4:

48. Casts & Molds molds and casts of organisms which have dissolved or rotted away, leaving only a trace of their existence. Casts and molds are types of fossils where the physical characteristics of organisms have been impressed onto rocks.  buried or trapped in mud, clay, or other materials which hardened around them - leaving molds of the organism. There are two types of molds:  external and internal.  Topic 4:

49. Topic 5: Page 603 Earth Textbook The process of gradual change that produces new life forms over geologic time. Fossils: Evidence for Evolution Natural Selection: survival of the fittest.

50. Topic 5: Page 603 Earth Textbook Fossils: Evidence for Evolution Relative-Age Dating: • Definition: Dating rocks and fossils by placing them in chronological order without exact dates. • Geologic Principles (used in this dating process): • Original Horizontality • Sedimentary rocks are deposited in horizontal layers • The Law of Superposition • in an undisturbed sequence the oldest rocks are at the bottom and each successive layer is younger • Principle of Cross-Cutting Relationships: • an intrusion or a fault is younger than the rock it cuts across