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geometrictiming - Deep Time How Old is Old Age of the Earth...

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Unformatted text preview: Deep Time: How Old is Old? Age of the Earth - A Historical Perspective Age Catastrophism Uniformitarianism Mud cracks now... Mud ... and mud cracks then Siccar Point, Scotland Point, Sedimentation of beds beneath the sea Sedimentation Deformation and erosion during mountain building Deformation Erosional surface cuts across deformed rocks Erosional Subsidence and subsequent deposition buries erosional surface Age of Mammals Multicellular life Age of Dinosaurs land plants Age of diversification Fig. 12.24 W. W. Norton Geologic time scale Unicellular life Two ways to date geologic events Two Absolute time and Radiometric Dating Absolute Break down Break W. W. Norton Radioactive decay and half-lives β– Radioactive decay schemes • 87Rb-87Sr • 147Sm-143Nd • 238U-206Pb • 235U-207Pb • 232Th-208Pb 87Rb 87 half-life 48 Ga half-life 106 Ga half-life 4.5 Ga half-life 0.7 Ga half-life 14 Ga 87Sr Organic matter Organic only Useful applications To archaeology Absolute dating technique using Absolute seasonal markings How old is Earth? How Relative Dating i-clicker question! When these sedimentary rocks formed, which layer was deposited first? M F R V L A. R B. L C. V D. M E. F Principle of Superposition Principle of Superposition i-clicker question! When the rocks were originally deposited: A. They were deposited at this angle. B. They were deposited at a steeper angle (closer to vertical). C. They were deposited at a shallower angle (closer to horizontal). Principle of original horizontality i-clicker question! When these rocks were deposited: A. No deposition occurred where the canyon is located. B. The rocks that make up the walls of the canyon continued across. C. Different rocks were deposited in the canyon. Principle of Original Continuity i-clicker question! Put the units in order from oldest to youngest: A. T, L, O, E B. L, T, O, E C. T, O, E, L E O L T Principle of Cross-Cutting Relations FAULTS Principle of Cross-Cutting Relations • What happened last? The sedimentary rocks, the dike, or the fault? Principle of inclusions Missing time… A B Which surface is an unconformity? A. B. C. C Unconformity in the GC Tapeats Sandstone Tapeats Sandstone (~550 million years old) Vishnu Schist Vishnu (~1700 million years old) Paleozoic Brachiopods Index Fossil- Trilobites Correlation correlation line What is missing?? Construction of a relative geologic Construction time scale ...
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