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Unveiling Earth’s Ages: Fossils, Dating & Time

Explore how scientists determine rock ages through fossils, radiometric dating, and Earth's history clues. Discover relative vs. absolute age dating methods in geologic science.

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Unveiling Earth’s Ages: Fossils, Dating & Time

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Presentation Transcript

  1. Semester Plan • Geologic Time • Meteorology • Astronomy • Oceanography

  2. How do scientists know the age of the rocks? How has life changed over time?

  3. Chapter 10 Clues to Earth’s Past EQ: How do scientists know the age of the rocks?

  4. Fossils • Fossils= preserved remains or evidence of ancient living things • Uniformitarianism is a basis of understanding Earth’s past

  5. Scaphognathuscrassirostris • Pterosaur – flying reptile • Germany during the Late Jurassic. It had a wingspan of about one meter.  The German scientist, August Goldfuss, discovered these bones in 1826. 

  6. D3.7 Difficulty in defining the past • Fossils only form when buried under sediment (preferably, moist) before decomposition occurs • difficult for remains of animals living in arid/semi-arid habitats to fossilize • Only hard parts of individuals fossilize (bones) • animal bodies are usually eaten by detritivores, decomposed by bacteria, or broken down chemically • Individual phenotype? • Of remains fossilized, most remain buried in sediment/remain unfound

  7. To do • Read pages 329 – 333 • Take notes on ‘Formation of Fossils’ and ‘Types of preservation.’

  8. 10.2 Relative age dating EQ: How dos scientists know the age of rocks? TODAY: 1. Blog: How can YOU become a fossil?

  9. D3.7 Difficulty in defining the past • Fossils only form when buried under sediment (preferably, moist) before decomposition occurs • difficult for remains of animals living in arid/semi-arid habitats to fossilize • Only hard parts of individuals fossilize (bones) • animal bodies are usually eaten by detritivores, decomposed by bacteria, or broken down chemically • Individual phenotype? • Of remains fossilized, most remain buried in sediment/remain unfound

  10. Relative age • Age of rocks and geologic features compared with other rocks and features nearby

  11. 10.3 Absolute age dating EQ: How do scientists determine the age of rocks? Today: 1. Have your relative age dating packet ready. Coming around to check

  12. Relative vs. Absolute Age Dating Relative Absolute Determine absolute date of the rock • Determines ages of rocks in order that they were formed but without exact dates

  13. Radiometric dating • Isotopes= atoms of the same element that have the same number of protons but different number of neutrons

  14. Carbon-14 dating • Radioactive decay: Some isotopes are unstable, emit radiation and decay into “daughter” isotope • Carbon-14 is unstable isotope and decays into nitrogen-14 • Over time: • The amount of “parent” isotope, carbon-14, decreases • The amount of “daughter” isotope, nitrogen-14, increases • The ratio of the two indicates the age of the rock • Half life: time required for half of parent isotope to decay into daughter isotopes • E.g. Half life of carbon 14 is approx. 5730 years

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