The Rock Record
Determining Relative Age
Mass Extinction• 65 million years ago (mya)– 50-85% of all species on
Earth became extinct.– In what geologic time period did this occur? (Page 8)– What are some species that became extinct?
• Questions: • How do we know that a mass extinction event occurred
65mya?• What caused the mass extinction?• Do you think it is important to understand what
happened? Why?
65 Million years ago
Resulting in Extinction
How do we know that organisms have become
extinct?
Studying the Past
• A thorough knowledge of the past is essential for understanding present and future processes.
Iridium found in thin layers of rock.
Iridium is foundin high concentrationswith in meteorites.
Studying Present Day
Old Faithful,YellowstoneNational Park
Studying Present DayYellowstone = SUPER VOLCANO
Past eruptionsand the resultingash deposits.
Why is this important?
Evidence of Tsunami in Chile
Why is this important?
Studying Present Day
Tsunami, Japan2011
Law of Superposition
Rock Layer A
Rock Layer B
Key Terms
• Law of Crosscutting Relationships• Uniformitarianism• Relative Age• Law of Superposition• Principle of Original Horizontality• Unconformities– Nonconformity– Angular unconformity– Disconformity
Define and providediagrams for each.
Key Terms (H)
• Inclusions• Index Fossils• Subsidence• Anticline• Syncline
Essential Questions
• 1. Explain why its important for scientists to be able to determine the relative ages of rocks.
• 2. State the Principle of Uniformitarianism in your own words.
• 3. Explain how the Law of Superposition can be used to determine the relative age of sedimentary rocks.
• 4. Explain the difference between an unconformity and a nonconformity.
Relative Age
What type of unconformity isfound here?
Which rock layeris oldest? Which is youngest?
AB
CD
E
disconformity
Slide 1Name theunconformity.
Angular unconformity
Slide 2: Sequence the Events
Slide 3: Sequence the Events
List the correctOrder of events.
Slide 4: Sequence the Events
Slide 5: Sequence the Events