how do we determine geologic age? 1.uniformitarianism = the processes that shape earth have not...
TRANSCRIPT
![Page 1: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/1.jpg)
How do we determine geologic age?
1. Uniformitarianism = the processes that shape Earth have not changed.
![Page 2: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/2.jpg)
Relative Age
2. Law of Superposition = rocks at bottom are oldest.
![Page 3: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/3.jpg)
Relative Age
3. Law of Horizontality = sediments deposit in horizontal layers.
![Page 4: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/4.jpg)
Explain This!
![Page 5: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/5.jpg)
Folding and Faulting
![Page 6: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/6.jpg)
Folding
![Page 7: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/7.jpg)
![Page 8: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/8.jpg)
Relative Age
4. Law of Crosscutting = features that cross other rock layer are younger than those layers.
![Page 9: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/9.jpg)
![Page 10: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/10.jpg)
![Page 11: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/11.jpg)
Unconformities
Uplift, erosion, and weatheringcan leave a missing piece to puzzle.
![Page 12: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/12.jpg)
Unconformities
![Page 13: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/13.jpg)
Determining Relative Age
![Page 14: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/14.jpg)
![Page 15: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/15.jpg)
How do we correlate rock layers from different locations?
![Page 16: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/16.jpg)
If locations are close together
Walk the outcrop:
Compare similarities like rock type, color, and mineral composition.
![Page 17: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/17.jpg)
If locations are far apart
1. Volcanic Ash – unique composition, short time span, and broad distribution.
![Page 18: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/18.jpg)
![Page 19: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/19.jpg)
If locations are far apart
2. Asteroid Impact – unique composition, short time span, broad distribution.
![Page 20: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/20.jpg)
K-T Boundary
![Page 21: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/21.jpg)
![Page 22: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/22.jpg)
If locations are far apart
3. Index Fossils – easily identifiable, short time span, and broad distribution.
![Page 23: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/23.jpg)
![Page 24: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/24.jpg)
Absolute Age
Radioactive decay = the decay of unstable isotopes (parent) into stable elements (daughter).
Isotope = element has different masses (or amount of neutrons).
Ex. Uranium 238 (radioactive) decays into Lead 206 (stable).
![Page 25: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/25.jpg)
Why use radioactivity?
1. Decay rate is predictable.
2. Immune to external forces: heat, pressure, chemical, and mass.
3. Decay begins:rocks: when formed. organic: when life ends.
![Page 26: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/26.jpg)
Half-Lifetime it takes for half or 50% of the parent to
decay into the daughter.
![Page 27: How do we determine geologic age? 1.Uniformitarianism = the processes that shape Earth have not changed](https://reader035.vdocuments.us/reader035/viewer/2022062511/5513e6fc55034674748b5729/html5/thumbnails/27.jpg)
Limitations
Air, Water, Life: C14 / C12 ratio is used for dating air, water, and organic material, but is limited to only ~50,000 years.
Rocks: radioactive isotope must be in rock.U238 date range: 10 million to 4.6 billionK40 date range: 50,000 to 4.6 billion