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Fossils

Fossils. Earth’s Age and Fossils. 1. The oldest rocks have been found in South America. They are over 4 Billion years old! 2. The oldest rocks on the moon are 4-4.6 billion years old. We think that the earth and the moon formed at about the same time. Why are earth’s younger? . Rock Layers.

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Fossils

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  1. Fossils

  2. Earth’s Age and Fossils • 1. The oldest rocks have been found in South America. They are over 4 Billion years old! • 2. The oldest rocks on the moon are 4-4.6 billion years old. We think that the earth and the moon formed at about the same time. Why are earth’s younger?

  3. Rock Layers • 3. The Law of Superposition states that the oldest rock layers are normally on the bottom. • 4. Cross cutting relationships says that an intrusion or fault is younger than the layers it cuts through.

  4. 5. An unconformity is when erosion results in a gap in the rock record.

  5. Relative Age and Absolute Age • Relative dating of rocks means that we define the age of rocks by surrounding layers of rock • 6. Relative age- No specific age is given. -I am older than my sister. • 7. Absolute age - A specific age is given. (Uses radioactive decay) • -Ex: That fossil is 65 million years old.

  6. Dating Fossils • Absolute dating is using the breakdown of radioactive elements to date an object. • 8.Radioactive decay is when one element decays (breaks down) into another element and releases radioactive particles. • 9. Radioactive elements have an unstable nucleus that breaks down over time. We can use this information to date things.

  7. 10. This decay rate always occurs at the same rate for the same element BUT the decay rate varies from element to element. • 11. The decay rate can be a few years, thousands or billions of years. • 12. Parent element decays to the daughter element.

  8. Radioactive Decay • 13. Example elements are: Rubidium -87, half life of 48.6 billion years. Decays to Strontium-87 • Uranium-238, half life of 4.5 billion years. Decays to Lead-206. • Carbon-14 decays to Nitrogen-14 in 5730 years. • 14. A half life is the time it takes for half of a radioactive substance to decay. • Ex: 1600g 800g400g 200g 100g 50g 25g 12.5g 6.25g 1st half life 2nd 3rd 4th 5th 6th 7th 8th

  9. Other methods… • 15. Other ways of dating include using tree rings, seasonal climate changes, and distinctive sediment layers. • Tree Rings- trees grow faster in summer than winter. Rings = years • Varves- glacial ice melts faster in summer than winter. Bands = years

  10. Earth’s History in FossilsFossils-clues to the past • 16. A fossil is the remains or evidence of a living thing. • 17. Most common are: bones, shells, pollen grains and seeds. Most are not complete organisms. The soft parts undergo decay.

  11. Index Fossils • 18. An index fossil lived only during a short period of time so we can use it to date common fossils found in the same area. Brachiopods Trilobites

  12. 19. Decayis the breakdown of dead organisms into the substances from which they were made. • 20. Most fossils are found in sedimentary rock. Being quickly covered by sediment doesn’t allow decay or other animals to destroy it.

  13. Fossil types continued… • 21.Mold- The is empty space left after decay that has same shape as organism. • 22. A cast is a mold that has been filled. Ex: Sea shells • Observe how fossils can form. • 23.Imprints are impressions made in soft mud that hardens. • Examples: leaves, feathers

  14. 24. Trace fossils- Fossils that mark evidence of an animal. Examples: footprints, tracks, burrows, etc.

  15. 25. Petrification-Once living material is replaced by minerals, turning it to stone. 26. Replacement may occur if water dissolves material but minerals in water replace the material. • Ex. Petrified Forest in Arizona.

  16. Preservation of entire organisms • 27. Very rare. Three ways. • Original Preservation- Soft and hard parts of animals remain 28. Freezing= Sudden weather changes preserve organisms before decay takes place. Ex. Wooly mammoths and very early people. Drawing of mammoth Actual preserved baby mammoth found frozen in Russia

  17. Amber • 29. Amber-Flies or insects get trapped in tree sap and it hardens. • Ex. Jurassic Park- his cane at • the beginning of the movie.

  18. Tar Pits • 30. Tar pits-Huge pits of tar. Usually near water-Animals would go drink & fall in. • Ex. Bison, camels, wolves, vultures, saber-toothed cats- The LaBrea Tar Pits- Seen in movie-Volcano and My Girl II.

  19. Interpreting Fossils • 31. Many different life forms have existed at different times through earth’s history. • 32. Scientists believe for every organism alive today at least 100 have gone extinct. • 33. Fossils show evolution, how earth’s surface has changed, past climates and appearance and activities of extinct animals.

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