Warm up

1. Warm up • Make sure your notebook is empty! (except for the 4 pages you got on your way in) • Please mark the HW AND the due dates up to 12/13 in your assignment book • How do scientists know Earth’s age? • What are fossils?

2. Geology and Earth's History... Honors

3. The Age of Enlightenment: • End of the 18th century (1700’s) • People began to look to science for answers: • How old is the Earth? • How was it formed? • New ideas were wearing down traditional ideas

4. The Age of Enlightenment: • Prevailing beliefs: • Earth was several thousand years old • Earth’s features (mountains, canyons, etc) were the result of rare but quick impacting catastrophes

5. James Hutton (1726-1797) • Born in Scotland • Apprenticed as a lawyer • Became a doctor • Successful farmer • Researched interests in Earth’s processes

6. James Hutton • Found fingers of granite in sedimentary rocks of Scotland • Saw as evidence of heat beneath the surface • Surmised that Earth’s core could make new rock

7. James Hutton • Neatly deposited layers of sedimentary rock over layers that were nearly vertical (see right) • Concluded the lower layers must have been deposited long ago, then later moved • In these unconformities between rock layers, he saw evidence of vast expanses of time in earth's history. Hutton’s drawing and the rock that inspired it at Siccar point Photo obtained at: http://honolulu.hawaii.edu/distance/gg101/Programs/program12%20Geologic%20Time/program12.html

8. James Hutton • Uniformitarianism • The processes working on the earth today are the same as those that have worked on the Earth in the past Hutton, James (1726-1797). "Theory of the Earth; or an Investigation of the laws observable in the composition, dissolution, and restoration of land upon the globe." Transactions of the Royal Society of Edinburgh, 1788, 1:209-304

9. Earth’s Geological Processes Catastrophism: All geologic processes (locally and globally) occur suddenly due to violent changes in the Earth Uniformitarianism: Processes shaping the earth (erosion, deposition, mountain building etc.) do not change over time but remain uniform vs. Today we see that both cause changes to the earth.

10. How do geologists know how old rock is? Law of Superposition: in undisturbed areas, younger rocks lie above older rocks Law of Cross-Cutting Relationships: Any geologic feature is younger than anything else that it cuts across

11. Law of Inclusions: If a rock contains fragments, the fragments are older than the rock they are in

12. Stratigraphy • Complete the Stratigraphy document • find the relative age of the layers in the rock sequences!

13. Warm up…(from your stratigraphy sheet)

14. Relative Dating: comparing the layers of rock to determine the order of formation Relative Time: time based upon relationships in rock layers

15. Relative Dating Given the colored “rock” layers: * Which layer is oldest? * Is the green rock older or younger than the pink rock?

16. But............... • Not all layers stay undisturbed • Forces push, tilt, fold, or break rock layers causing them to be out of their normal sequence • Data from known, undisturbed rock layer sequences are used to identify difficult or puzzling rock sequences • Geologic Column can help identify the relative age of rock layers.

17. Relative Age & Unconformity Brain Teaser ***List the rock layers and unconformities in order from oldest to youngest. NOTE: All the rock layers are sedimentary rocks except the igneous intrusions A and E and the fault line H

18. Some words to know… Paleontology the study of fossils Fossils: remnants of past life/living things Paleontology teaches us about changes to life on the planet It integrates Biology and Geology

19. Now… Complete the Who’s On First Activity This is part of your Conference Packet

20. Warm up

21. Absolute Dating: A Measure of Time...

22. Absolute Dating... • Establishing the age of an object in numbers of years • Uses Radiometric (radioactive) dating

23. In this compound, are all the atoms of a given element exactly the same? Why or why not?

24. Isotopes of an element have the same chemical properties but different atomic weights.

25. Isotopes Isotopes - Different forms of an element having the same number of protons but different numbers of neutrons (and therefore different atomic weights).

26. 1913: T. W. Richards found two atomic masses for lead. • 1919: F. W. Aston separated neon atoms into two different isotopes • invented the mass spectrograph. • Today: many isotopes of the elements have been discovered.

27. Atomic Structure: Mapping an Invisible World. AIMS Multimedia. 1996. unitedstreaming. 4 January 2007 <http://www.unitedstreaming.com/>

28.  1 H Hydrogen 1.00794 To the right is some of the chemical information for the element Hydrogen. When you look at the periodic table of the elements, why is the atomic mass for each element a decimal rather than a whole number?

29. Naturally occurring chemical elements are usually mixtures of isotopes, and so their atomic masses are weighted averages of the masses of the isotopes in the mixture.

30. Radiometric Dating • Radioactive elements are unstable and change to become stable Stable Isotope Aka “Daughter” Unstable Isotope Aka “Parent”

31. Radioametric Dating • Measure the amount of breakdown of radioactive atoms in rocks to determine its age • Half-Life- time it takes for 1/2 of the radioactive atoms to decay into a stable isotope • Rate of breakdown is constant • Example: half-life for C14 is 5,730 years 12g of C14 decays to 6g after 5,730 years

32. Radioametric Dating • Carbon-14: half-life is 5,730 years • mainly used for things up to 50,000 years old • Very helpful for organic material • Uranium-Lead : half-life 713 million years • Potassium-Argon: half-life 1.26 billion years

33. Half Life Ratios • 1 half life = ½ radioactive • 2 half lives = ¼ radioactive • 3 half lives = 1/8 radioactive • 4 half lives = 1/16 radioactive

34. DIRECTIONS • Set up a table for the problems that includes Time, Unstable Amount, and Stable Amount Example: Scientist found a sample of bone and found that 6.25% of the total carbon 14 was left. Determine the age of the bone.

35. Example: Scientist found a sample of bone and found that 6.25% of the total carbon 14 was left. Determine the age of the bone. (C-14 Half-life is 5,730 years)