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Geologic Time

Explore the "It's So Obvious" laws in geologic time with relative age dating. Understand Uniformitarianism, Catastrophism, and the Laws of Stratification, Superposition, Original Horizontality, and Cross-cutting Relationships. Discover the Principle of Fossil Succession and how index fossils help determine geological ages. Delve into nonlinguistic representations to visualize Earth's shaping laws in action.

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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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