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  1. 1. Fossils Ch 6 Section 4 P. 166-171
  2. 2. Fossil <ul><li>The remains or physical evidence of an organism preserved by geological processes. </li></ul><ul><ul><li>Most often preserved in sedimentary rock. </li></ul></ul><ul><ul><li>Sediment slows down decay. </li></ul></ul><ul><ul><li>Bones and shells resistant to decay, so they are more commonly preserved than soft tissue. </li></ul></ul>
  3. 3. Fossils Continued <ul><li>Fossil Examples </li></ul><ul><li>1) Fossils in rock </li></ul><ul><li>2) Fossils in amber (amber means tree sap) (fossils in tree sap) </li></ul><ul><li>3) Petrification the organism's (plant or animal) tissue is replaced by minerals </li></ul><ul><li>4) Fossils in asphalt (pavement) </li></ul><ul><li>5) Frozen Fossils </li></ul><ul><li>6) Trace Fossils a fossilized mark that is formed in soft sediment by the movement of an animal. (dinosaur tracks, dear tracks, tail markings) </li></ul><ul><li>7) Mold a mark or cavity made in a sedimentary surface by a shell or other body. </li></ul><ul><li>(indentation in rock) </li></ul><ul><li>8) Cast a type of fossil that forms when sediment fills in the cavity left by a </li></ul><ul><li>decomposed organism. (object is created, like the TREX tooth) </li></ul><ul><li>Index Fossil a fossil that is found in only one geologic rock layer and is used to find the age of the rock layers. </li></ul>
  4. 4. Amber Fossils <ul><li>Hardened tree sap </li></ul><ul><ul><li>Bugs, lizards and frogs found here. </li></ul></ul>
  5. 5. Petrified Fossils <ul><li>A process in which minerals replace the organism’s tissues. </li></ul><ul><ul><li>Different types: </li></ul></ul><ul><ul><ul><li>Pore space in bone/wood fills up with mineral </li></ul></ul></ul><ul><ul><ul><li>Organisms tissues are replaced by minerals </li></ul></ul></ul>
  6. 6. Fossils in Asphalt <ul><li>Asphalt wells up in thick sticky pools. </li></ul><ul><li>Trapped and preserved organisms in asphalt. </li></ul>
  7. 7. Frozen Fossils <ul><li>Cold temperatures slow down decay. </li></ul><ul><li>Many types of frozen fossils are preserved from the last ice age. </li></ul>
  8. 8. Trace Fossils <ul><li>Any naturally preserved evidence of animal activity. </li></ul><ul><li>Footprints fill with sediment. </li></ul><ul><ul><li>Tracks reveal how big the animal was & how fast it moved. </li></ul></ul><ul><ul><li>Shelters made by animals. </li></ul></ul><ul><ul><li>Animal poop </li></ul></ul>
  9. 9. Molds and Casts <ul><li>Mold: A cavity in rock where a plant or animal was buried. </li></ul><ul><li>Cast: an object created when sediment fills a mold and becomes a rock. </li></ul>
  10. 10. Fossils on a Mountaintop? <ul><li>Rock on the mountain formed at the bottom of the ocean. </li></ul><ul><li>Using fossils, scientists can tell whether the climate was cooler or wetter than present. </li></ul>
  11. 11. Fossils Help Date Rocks <ul><li>Index Fossils: fossils of organisms that lived during a relatively short, well-defined geologic time span. </li></ul>