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