Rocks Provide a Timeline for Earth

1. Rocks Provide a Timeline for Earth Notes for section 4.2

2. First Let’s Review! Make sure your Clickers are on!

3. 0 Index fossils are unique because they are only found during a specific span of time. • True • False

4. 0 Fossils can only be found in sedimentary rock. • True • False

5. 0 When looking at a core sample, the oldest layer is • On the top • At the bottom • In the middle • All of the above

6. 0 Why are fossils only found in sedimentary rock? • Because heat destroys fossils evidence • Animals only live in areas that have sedimentary rocks • Sedimentary rocks do not use heat when formed • Both 1 and 3

7. 0 What can scientists learn from core samples? • Climate and other geologic activity • Changes that occurred over time • Life that lived during different spans of time • All of the above

8. Time for Notes!!!!!

9. The Big Idea! Rocks and fossils provide a timeline for the Earth

10. Watch this short video to learn more!

11. Layers of sedimentary rocks show relative age • Geologists reconstruct the past using the relative ages of objects or events based on clues • For example-magazine activity • Relative age is the age of an event or object in relation to other events or objects. • Let’s take a look at this link to learn more! http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage3.html

12. Do you remember how sedimentary rocks are formed?

13. Sedimentary rocks form from things that have been eroded and carried away to another area (deposition) • Minerals act as glue to cement the layers together • Over time, the sediments pile up to form horizontal layers of sedimentary rocks • This is called the Law of Superposition • Bottom layer forms first which means it is the oldest • So what does that tell us about the top layer?

14. Index Fossils • Index fossils are: • fossils of organisms that were common • lived in many areas • existed only during specific spans of time • This information is used to determine its relative age and therefore the relative age of the rock.

15. Radioactive Dating can show absolute age • When we know the exact age of an object or event, we know its absolute age • To determine the absolute age of an object scientists must examine the elements and see the rate at which they break down. • This is called radioactive dating or radiometric dating • http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage8a.html

16. Did you know???? • Scientists used radiometric dating to estimate that the Earth is 4.6 billion years old!

17. Using Absolute and Relative Age • Scientists must use all methods to determine the age of objects and events in order to figure out the Earth’s past!

18. 10 Radioactive dating determines the relative age of an object. • True • False

19. 20 Which one is NOT a characteristic of an index fossil? • They are common • They are found in several layers • Only exist during one span of time • Can be found in many areas

20. 15 If you tell someone that you are 12 years old, are you giving your…. • Index age • Half-life • Relative age • Absolute age

21. 10 Scientists use the absolute or relative age of a fossil to determine the age of the rock. • True • False