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Geologic Time

Geologic Time. Using the rock record to age date rock layers. Let’s Start Thinking About This…. You go to your refrigerator and look at the leftovers you wrapped in clear plastic wrap over the past 4 weeks but forgot to date. How would you determine which is freshest and which is oldest?.

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Geologic Time

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  1. Geologic Time Using the rock record to age date rock layers

  2. Let’s Start Thinking About This… • You go to your refrigerator and look at the leftovers you wrapped in clear plastic wrap over the past 4 weeks but forgot to date. • How would you determine which is freshest and which is oldest?

  3. Relative Age Dating • Geoscientists have devised a set of laws to help us understand the processes that shape our Earth • I call them the “It’s So Obvious” Laws

  4. Relative Age Dating • Uniformitarianism- Earth’s processes are slow & gradual and have remained the same over time • (rock cycle, water cycle, climate, etc.) • If you know how a rock formed 1 thousand years ago… • then you know how the same type of rock formed 3 billion years ago

  5. Uniformitarianism The principle that the Earth has been shaped by GRADUAL changes throughout history and is shaped by GRADUAL changes that are still occurring.

  6. Catastrophism • Sudden, violent changes that shape the geologic structure of Earth.

  7. Relative Age Dating • Relative age dating is the science of determining the relative order of past events, without necessarily determining their absolute age.

  8. Relative Age Dating • Law of Stratification • rocks form in layers or strata • By looking at the surrounding layers, geoscientists can infer the relative ageof a rock layer.

  9. Relative Age Dating • Law of Superposition • Oldest rocks on the bottom • Youngest rocks on the top

  10. Relative Age Dating • Law of Original Horizontality • Layers originally deposited horizontally • If they are folded or tilted… • Then they have been disturbed or disrupted • Remember the Geologic Column? • NO SINGLE LOCATION ON EARTH HAS A CONTINUOUS SEQUENCE OF ALL THE ROCKS FORMED IN HISTORY

  11. Relative Age Dating • Law of Cross-cutting Relationships • Rock faults or intrusions that cut through rock layers must be younger than the layers • Fault – A break in the Earth’s crust along which blocks of the crust slide relative to one another.

  12. RelativeAge Dating • Principle of Fossil Succession • fossils succeed each other in a definite order • Index Fossils Can you remember how this statement can apply to astronomy?

  13. Using Index Fossils • Index Fossil Demo

  14. How do Fossils Form? • http://www.discoveringfossils.co.uk/Whatisafossil.htm • https://www.youtube.com/watch?v=c_DCP4cLVNg (play up to 5min mark)

  15. Nonlinguistic Representation • You are in charge of developing a non-linguistic graphic representation or illustration to allow the world to know more about the laws that shape out Earth aka the “It’s so obvious” laws. Below are the requirements: • The artwork must demonstrate the concept in a real-life situation (at least 3 laws or principles) • The centerpiece of the artwork must be a slogan or phase • 4 colors must be used

  16. Slogan "Superposition Pizzeria: We'll deliver in 30 minutes or less without any folds or tilts!"

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