Unit 3 Earth History: Day 7 Focus: Absolute Age/Half-Life/quiz 12/14/17 Get your clicker. Copy this E.Q. on page 43. E.Q. How can elements in rocks help us know the exact age of those rocks?

Three fossils are not present in Layer D. How might we explain this? A. Based on the Law of Superposition, which layer is the oldest? B. Youngest? A. Which outcrop(s) contains an unconformity? B. What may have caused it? A. Based on prior discussions, which fossils in this diagram may serve as index fossils? B. Why? A. What do these 4 fossils have in common? B. If these are some of the earliest organisms on the planet, what can we infer about life on our planet? Three fossils are not present in Layer D. How might we explain this? If scientists know the age of the trilobite, what can they infer? Brachiopod

1. Sequence the layers and events from oldest to youngest. 2.What is D? 3.What is C? 4.What is A? D is a fault. C is an igneous intrusion. A is an unconformity.

Plan for the Day 1. Review and practice problems on Absolute Age-Dating of Rock *Brainpop Video- Carbon-14 *Half-life practice activities 2. Quiz 3. Bill Nye – “Fossils”

Half-Life Practice Problems wkst. (on back of the notes) Homework

Earth History Theories Uniformitarianism – James Hutton Earth is much older than previously thought. Most geologic change is gradual/slow (processes like erosion and deposition) Processes that shape Earth’s surface today also shaped it in the past 2. Catastrophism – The Church and most scientists of Hutton’s time Earth is only a few thousand years old –young Most geologic change is a result of rare, sudden, catastrophic events (earthquakes, asteroid impacts, volcanoes, floods) Quick changes to Earth’s surface features

How can elements in rocks help us know the exact age of those rocks? Essential Question – How can elements in rocks help us know the exact age of those rocks?

Radioactive Decay and Half-Life “Parent” element ”Daughter” element After four half-lives, only 1/16th of the parent element remains; the rest of it has decayed into daughter element. After one half-life, only one-half (1/2) of the parent element remains; half of it has decayed into daughter element. After two half-lives, only 1/4th of the parent element remains; ¾ of it has decayed into daughter element. After three half-lives, only 1/8th of the parent element remains; 7/8 of it has decayed into daughter element. Igneous rock first forms-100% parent element ***Assuming the parent element has a rate of decay (half-life) of 10,000 years

Let’s see what Brainpop has to say about Absolute Dating using a radioactive substance called Carbon-14. Brainpop on Radiocarbon (Carbon - 14) dating

Let’s do one more half-life practice activity: a. Brainpop - calculator

Quiz time – 15 questions – Read them carefully.

Wrap-up: What percentage of radioactive –PARENT- element would remain in a rock sample after one half-life? Two half-lives?