Today

1. Today Hand in any work needed. Get out a small piece of paper, PUT YOUR NAME ON IT. When bell rings the quiz will start and you will have 1 minute per question to answer.

2. Question 1 When were the earliest birds?

3. Question 2 When did dinosaurs go extinct?

4. Question 3 • Give me the LAT/LONG of Old Forge and what kind of fossils are there?

5. Question 4 When was the “peak development of eurypterids”

6. Answers • 1.) When were the earliest birds? • Jurassic • 2.) When did dinosaurs go extinct? • 65 MYA • 3.) Give me the LAT/LONG of Old Forge • and what kind of fossils are there? • 43o 45’ N 74o 45’ W no fossils • 4.) When was the “peak development of eurypterids” • Silurian

7. Radioactive decay

8. Vocab • Radiometric isotope (parent isotope) • The original element. • Daughter isotope • The new element after decay. • Half-life

9. What the heck? • What is this? • Radioactive decay means to: • Break down over time. • Certain elements decay over time. They release electrons which changes element. • By looking at what and how much of an element there is, you now how old it is.

10. How Carbon will break down

11. What's a half life? A half life is how long it takes for ½ (50%) of the amount to decay into its daughter isotope.

12. Why Different elements? • Carbon (C) good for short time periods. Thousands of years. • Dates humans, things from last ice age. • Potassium (K) good for long periods millions of years • Uranium (U) good for long terms millions of years. • Oldest rocks on Earth.

13. Strontium dating All elements will decay over time. Eventually there will be so little left that it cannot be dated. After 175 years there is less than 1% left of the original. All elements graphs lookthe same!

14. Carbon-14 • Carbon (half live = 5700 years) so, • ½ the amount is left after 5700 years, • ¼ the amount is left after 5700 x 2 = 11400 years • 1/8 the amount is left after 5700 x 3 = 17100 years

15. Try it Try this: • If I start with 100 grams of sugar. And I know that sugars half life is 2 years. • So in 2 years I will have 50 grams of sugar left… • In 4 year I have • In 6 years I have Every 2 years is one half life, so how many did I go through here? OR

16. 2 Years 4 Years 6 Years • 12.5% • 12.5% • Sugar • 25% • 50%

17. For real • How many half lives did the element carbon go through if there is only 6.25g left of the original sample of 100g? 100 -> 50 -> 25 -> 12.5 -> 6.25 So, 4 half lives

18. Again, try this How long does it take Carbon-14 to decay 2 half lives? One HL = 5.7 x103 years or 5700 years Two HL = (5700 x 2) 11,400 years And so on..

19. Last one • Uranium-238 is taken from a rock. It is found to be 10g. Over 5 Half lives what was the original amount and how old is it? • DRAW IT OUT ON CHART!! • First, HL of U-238 is 4.5x 109 years or 4,500,000,000 years. • How many half lives are there needed? • 5 • (5 times 4,500,000,000) 2.25x1010 or 22,500,000,000 years • 10 -> 20 -> 40 -> 80 -> 160 -> 320 grams started