1. Do First Actions: Turn in yesterday’s worksheet 1. List the layers from youngest to oldest

2. Agenda 1.Absolute Dating Notes 2.Absolute Dating Practice

3. Absolute Dating

4. What is Absolute Dating? Absolute Dating provides an actual age to something Which example below is an example of absolute dating? – This rock is 500 million years old and this rock is 3,000 years old – This rock formed first and then this rock formed next

5. Radiometric dating A common type of absolute dating is radiometric dating or radioactive dating Radioactive dating is the process of determining the age of rocks or minerals from the decay of their radioactive elements

6. What is a Half-Life? We measure rate of decay in Half-Life A Half-Life is the amount of time required for the mass of atom to fall to half its initial value. The rate of decay is not affected by external factors such as temperature, heat or pressure. The original atom is known as the parent product and the resulting half is known as the daughter product

7. The Decay Process Shade in the particles to represent the decay process

9. Using Half-Lives By comparing the ratio of Parent product to daughter product you can calculate the number of half-lives that have passed

10. Using Half-Lives Half-lives are specific to different isotopes Materials with long half-lives are used to date old materials – Uranium -235 has a half-life of 700 million years – Uranium -238 has a half-life of 4.5 billion years Materials with short half-lives are used to date young materials – Carbon – 14 has a half-life of 5,730 years – Carbon dating is only useful up to 70,000 years

11. Would I use Carbon or Uranium to radiometric date the following? Dinosaurs? Humans? The Age of the Earth?

12. Radiocarbon Dating When the organism dies the C 14 inside of it begins to decay In Carbon dating, the amount of Carbon-14 is compared to amount of Carbon-12

13. Uranium Dating The age of the Earth was determined by the breakdown of different isotopes of uranium. In Uranium dating, the amount of Uranium- 238 is compared to amount of Lead - 206

15. Absolute Dating Problems

16. Problem 1 The following fossil starts with 24 grams of carbon. It loses ½ of that every 1000 years. How old is it when it has: a.24 grams: 0 years old b.12 grams: 1,000 years old c.6 grams: 2,000 years old

17. Problem 2 The following fossil starts with 48 grams of carbon. It loses ½ of that every 2 million years. How much carbon is left after: a.1 half life: 24 grams b.2 half-lives: 12 grams c.3 half-lives: 6 grams

18. Problem 3 What % of Carbon – 14 is remaining after 11,540 years? 25% What % of Carbon – 12 is remaining after 11,540 years? 75%

19. Problem 4 How many half-lives have occurred when only 25% of the parent material is left? 2 Half lives

20. Practice

21. DYL If an organism began with 20 g of Carbon-14 and now has 5 g. 1. How many half-lives have passed? 2. If each half-life is 1500 years, how many years have passed?4