What’s the oldest thing you have ever touched?

1. What’s the oldest thing you have ever touched?

2. Evolution of Landforms and Organisms Continued – Part Two

3. Geology –Study of the EarthGeologic Terms

4. Age of Earth?thousands - millions - billionstrillions 4.6 Billion Years old

5. How is the Age of the Earth Determined? Relative Age Absolute Age

6. Relative Age or Absolute Age“No Ordinary Family”

7. Absolute Age and Rocks • Absolute age tells the actual age of a rock. • Radioactive Decay or Radiometric Dating is one method that gives the age of a rock by comparing the amount of radioactive material in the rock with the amount that has decayed

8. Radioactive Dating - Carbon Dating • The half-lifeof a radioactive element is the time it takes for half of its atoms todecayinto something else. • For example, thehalf-lifeof radium-226 is 1600 • Therefore, in 1600 years, one gram of radium-226 will turn into half a gram of radium-226 and half a gram of something else • After another 1600 years have elapsed, only a quarter of a gram of the original radium-226 will remain. • Finding the ratio of parent to daughter elements • Carbon-14 is an isotope that has a half life of 5,700 year old. • Half-life – The time it takes for half of the atoms in an isotope to decay • Radiometric Decay – Process that uses properties of atoms in rocks and other objects to determine their ages. • Radioactive Dating – calculating the absolute age of a rock by measuring the amounts of parent and daughter materials in a rock and by knowing the half-life of the parent material

9. Every living thing containsCarbon -14 • It has been used to date fossils such as frozen mammoths, pre-historic humans, plants and animals that lived up to about 50,000 years ago. • It’s half-life is only 5,700 years so it can’t be used to date ancient fossils or rocks. Carbon dating tells when this mammoth died

10. Elements Used in Radioactive Dating

11. Calculating Half Life • Carbon-14 decreases by half every 5,700 years. • A sample of 1g of carbon-14 will decrease by half to 0.5 after 5,700 years • How much carbon-14 will there be in 17,100 years? • 0.125 g • 0.8 g • 0.1 g • 0.025 g 5,700 is 3 times more than 17,100 • Divide 5,700 / 17,100 = 3 • 1g X 0.5 = 0.5 • 0.5 X 0.5 = 0.25 • 0.25 x 0.5 = 0.125g

12. Determining the Absolute Age of Rock LayersRadioactive Dating A technique for measuring the age of an object or sample of material by determining the ratio of the concentration of a radioisotope to that of a stable isotope in it; for example, the ratio of carbon-14 to carbon-12 reveals the approximate age of bones, pieces of wood, and other archeological specimens.

13. Blocks • Stack the blocks • Do not stack according to size • Which block is the oldest ? • Which block is thy youngest?

14. In undisturbed sedimentaryROCK, the oldest layers are deeper down, at the bottom and the youngestlayers are closer to the top. Kids are younger & come after parents & grandparents. Kids Parents Grandparents Great-grandparents Law of Superposition

15. Law of Superposition – Rock Layers • This law states that if a rock layer has not been disturbed then; • Older layers of rock lie beneath younger rock layers • This should make sense • The oldest sediments must be laid down before the younger ones can pile up on top.

16. Rock Layers

17. Blocks • Which block is the oldest ? • Which block is thy youngest? Tilt the blocks to at an angle. What happens to the rock layers when they are tilted?

18. Blocks • Which block is the oldest ? • Which block is thy youngest? Continue tilting the blocks until the layers have reversed positions. Now….

19. Unconformity • Plate movements can fold, tilt or turn rock layers • An unconformityis a “missing”rock layer • This sometimes makes it difficult to age rock layers • An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic record.

20. UnconformityIgneous or metamorphic rock is a nonconformity. The boundary represents a nonconformity. Igneous or metamorphic rock may be uplifted to Earth’s surface by crustal movements. Once the rock is exposed, it erodes. Sediments are deposited on the eroded surface.

21. Angular Unconformity The most obvious kind is the angularunconformity. Rocks below the unconformity are tilted and sheared off, and rocks above it are level. The angular unconformity tells a clear story: • First a set of rocks was laid down. • Then these rocks were tilted, then eroded down to a level surface. • Then a younger set of rocks was laid down on top.

22. Angular Unconformity An angular unconformity forms when rock deposited in horizontal layers is folded or tilted and then eroded. When erosion stops, a new horizontal layer is deposited on top of a tilted layer. When the bedding planes of the older rock layers are not parallel to those of the younger rock layers deposited above them, an angular unconformity results.

23. Water Causes Mechanical and Chemical Weathering Iron oxidation water expands when it freezes

24. Chemical Weathering The main agent of chemical weathering is WATER Rocks react with water, gases and solutions (may be acidic); will add or remove elements from minerals.

25. Why is the Statue of LibertyGreen? The statue is made of copper. Copper is naturally the color of a shiny penny. But, when copper is exposed to rain it tarnishes. This is chemical weathering. The rain contains copper carbonate, maybe sulfuric acid which gives it the green color. It turns the statue into copper oxide and other elements due to “oxidation”.

26. Mechanical Weathering • Thermal expansion – heating and coolingof rocks • heat causes expansion; cooling causes contraction. • Freezeing –Thawing action of water in the cracks of rocks water expandswhen it freezes

27. Mechanical Weathering • Animals can burrow beneath the ground and break up rocks and soil • Plant roots can grow and crack and break up rocks and soil

28. The salts in our oceans is a result of weathering of rocks and soil. • One way minerals and salts are deposited into the oceans is from outflow from rivers, which drain the landscape, thus causing the oceans to be salty. Rain contains some dissolved carbon dioxide from the surrounding air. This causes it to be slightly acidic. The rainphysically erodes the rock and the acids chemically break down the rocks and carries salts and minerals into the oceans

29. Weathering Created the Grand Canyon

30. Ice Cores • Studying ice cores helps in • understanding how climate has changed - warmer and/or colder • Ice forms layers similar to rock layers • We have also learned about the Ice Ages by discovering fossils that are missing in rock layers. • The layers record amounts of gases and elements present in the atmosphere and water at a particular time in history

31. Ice Core

32. Paleontologists Paleontologists study fossils they find embedded in “sedimentary” rocks. They use the information to determine what the earth and life was like in the past. The fossil record explains about life in the past and how it and the environment has changed over time. The rest of ANSWER # 17 ison another slide - Put your pencil down

33. Fossils are our window to the past. They show us what life was like millions of years ago.

34. They are evidence of once-living things. They show how species have changed over time and how some species are related to one another. Fossils

35. Fossils can give us evidence of past lifeFossils suggest that birdsevolved from dinosaurs.

36. A fossil is a rock! Most fossils are formed of sedimentary rock. They are formed by compacting and cementing together layered sediments.

37. Most Fossils form in What Kind of Rock ? • Layer upon layer of sand, mud, dead plants and animals and other small pieces build up and their weight compacts and cements the layers together.

38. Fossils form Slowly • It takes about 1 million years to form a sedimentary fossil.

39. Deposition + Time + Erosion = Fossils

40. ANSWERS for # 17 - Fossils Facts • They give us evidence of past life • Most fossils are found in sedimentary rocks • Fossils form slowly • Only the hard parts of an organism is preserved • An organism has to be buried quicklyin order to become fossilized. • They give us clues about the size, shape, growth patterns and structures of extinct organisms. • They show us how organisms have changed over time • They show us how organisms are related to one another.

41. Preserved Tracks • Tracks give us evidence of the size, weight and stride of the animal. If several tracks are found that can be evidence of lifestyle: social grouping an interactions among species.

42. Here’s the Story! • Sometime between 200 and 205 million years ago a meat eating Eubrontes dinosaur crouched on the shore of lake Dixie. Perhaps it had been eating fish in the nearby deep water. The dinosaur may have been a Dilophosaurus weighing around 1,000 pounds, measuring 6 feet high at the hip and 18 feet long. He sat down leaving the imprint of his feet, heel, pelvis, hands, and tail in the sand. In the process of getting up he shuffled his feet, leaving a second set of impressions. He arose and walked away. For some reason his impressions were buried waiting to be discovered at a later date.

43. Here’s the Proof!

44. Index Fossils • Some species inhabited Earth for long periods of time without changing. • INDEX FOSSILSexisted for short periods of time, were abundant and were found in lots of different places on Earth. • Index Fossils have been found in many places throughout the Earth and geologists use them to date the age of rock layers. Sea Urchin Ammonite

45. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geologic time periods

46. Geologic Time Scale

47. Geologic Time ScaleA timeline that organizes the events in Earth’s history.The divisions are based onorganismsthat existed during that time period and thegeologic events that occurred: mountains forming, seas rising, plains forming, etc…

49. Age of Mammals Organisms that existed during the Cenozoic Mesozoic Paleozoic Eras Age of Reptiles Age of Fishes

50. Quiz