Downloaded 224 times
More Related Content
Similar to relative-and-absolute-dating_earth-science.pptx
relative-and-absolute-dating_earth-science.pptx
- 1.
- 2.
- 3. HOW DO WE KNOWTHE AGE OF FOSSILS? -Scientists use 2 methods to determine the age of fossils: 1. Relative Dating 2. Absolute Dating
- 4. Relative and AbsoluteDating
- 5. What is Dating? Whengeologists date rocks, they are determining how long ago they formed. Two ways to do this: Relative Dating Absolute Dating
- 6. Relative Dating Determining howold something is compared to something else Use words like “older” or “younger” instead of exact numbers
- 7. I. Relative Dating RelativeDating is when you give the age of a rock or fossil compared to another rock or fossil. Example: Rock A is OLDER than Rock B. An actual age in years is not determined.
- 8.
- 9. II. Rules ofRelative Dating 1. Law of Superposition: When sedimentary rock layers are deposited, younger layers are on top of older deposits.
- 10. Rules of RelativeDating 2. Law of Original Horizontality: Sedimentary rock layers are deposited horizontally. If they are tilted, folded, or broken, it happened later.
- 11. Rules of RelativeDating 3. Law of Cross-Cutting Relationships: If an igneous intrusion or a fault cuts through existing rocks, the intrusion/fault is YOUNGER than the rock it cuts through
- 12. Order these layersfrom oldest to youngest Youngest layer Oldest layer
- 14. Order the eventsfrom oldest to youngest Fault Gray Layer Multicolored layer Spotted Layer OLDEST LAYER/EVENT YOUNGEST LAYER/EVENT
- 15. III. Correlation Rock layersin different places can be correlated or matched up by matching up the rocks and fossils in the layers.
- 16. IV. Unconformity When rockhas been eroded, so you have a missing section of time in the rock record.
- 17.
- 18. Why are someof the layers tilted? What happened to the top of the folded rocks? The missing rock layers is called an __________.
- 19. What type of rocksformed above? What events might have caused the rock layers to become tilted? Why is the top flat? What caused the angular unconformity?
- 20. Index Fossils Some speciesof organisms only lived for a short period of time before they became extinct. If you use radiometric dating to get an age for the fossil, then you know that the rock the fossil is found in is also that age. Trilobite: Index fossil for the Paleozoic Era Age: 590-250 mya
- 21. Graptolite Index Fossil ofthe Ordovician Period Age: 500-335 mya
- 22. Fossil B lived10 million years ago – 2 million years ago. Fossil A lived 20 million years ago- 8 million years ago. What do you know about the age of the rock containing both fossils?
- 25.
- 26. What is “B”? Place the layers in order from oldest to youngest
- 27. Put the eventsin order
- 28. Put the eventsin order
- 29.
- 30. Youngest_____ _____ __________ _____ _____Oldest
- 31.
- 32. Youngest ____ ________ ____ ____ ____ ____ ____ _____ _____ Oldest
- 33. Make your ownStrata Sequence Requirements: • One of each: Igneous intrusion, faulting, folding, erosion • Each rock type needs the correct symbol • Neatness – use a ruler • Key for rock types • Separate Answer key
- 35. Absolute Dating Determining howold something is Use numbers (in millions of years, mya) Only works for Igneous Rocks
- 36. Absolute Dating Determines thespecific age of a fossil Looks at chemical properties 2 types: Carbon-14 (radiocarbon) Potassium-Argon
- 37. Carbon-14 Dating Also knownas Radiocarbon dating Used to date organic substances Scientists measure the radiocarbon in the fossil to determine its age Can only date specimens up to about 60,000 years old
- 38. Potassium-Argon Dating Scientists determinethe age of the rock surrounding the fossil to determine the fossil’s age. Used only for inorganic substances (rocks and minerals) Scientists measure the amount of argon in the rock to determine its age Dates rock 60,000 years old and older
- 39. How Absolute DatingWorks When magma/lava cools, radioactive elements are incorporated into the minerals Examples: -- Potassium 40 -- Uranium 235
- 40. How Absolute DatingWorks These elements begin to decay at a known rate starting when the rock cools We can measure how much of the element is left Tells us how much time has passed since the rock formed.
- 42. What can welearn from this? T-Rex Fossil Geologist Basalt, dated to 80 mya Basalt flow, dated to 100 mya Sandstone So when did this T-Rex live? Between 100 and 80 mya This may not seem very accurate, but compared to the 4,500 million years the earth has been around it gives us a lot more information than we had before
- 43. What can welearn from this? Absolute Dating Helps us determine the age of the earth Helps us determine when specific events in the history of the earth happened (ex. Extinction of the dinosaurs) Relative Dating Can help us estimate the time span between major earthquakes, storms, tsunamis etc Can help us determine the order that life forms developed on earth
- 45.
- 46. Which rock layeris the oldest? Youngest? Oldest Youngest
- 47. If you wantedto figure out the exact age of a rock, what technique would you use? a.Relative Dating b.Carbon-14 Dating c.Law of Superposition d.Potassium-Argon Dating
- 48. If you werelooking to find the exact age of a fossil that is at least 1 million years old, what technique would you use? a. Carbon-14 Dating b. Potassium-Argon Dating c. Relative Dating d. You can’t; it is impossible
- 49. If you wantedto figure out the exact age of a fossil that is less than 40,000 years old, what technique would you use? a. Carbon-14 Dating b. Potassium-Argon Dating c. Relative Dating d. You can’t; it is impossible