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Discover the various ways fossils can form, including original remains, replaced remains, molds and casts, trace fossils, and carbonaceous films. Learn about the different methods used by paleontologists to study fossils.
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Formation of Fossils What are fossils? • Any evidence of earlier life preserved in rock. • Are studied by paleontologist. • What is paleontology • The study of life in prehistoric times.
Formation of Fossils What are some ways fossils can form? • Original remains • Replace Remains • Molds and cast • Trace fossils • Carbonaceous films
Formation of fossils Original Remains What do you think they are? • These are the unchanged remains of plants and animals. • Ex. Frozen wooly mammoth in Alaska/ Russia • Ex. An insect trapped in amber (hardened tree sap)
Formation of fossils Replaced Remains What do you think these are? • After the soft parts decay the remaining hard parts (bones, teeth, shells…) are replaced by rock forming minerals. • Ex. Petrified wood
Formation of fossils Molds and Cast How are they formed? Step 1: organism dies and is buried in sediment Step 2: Hard parts fossilize as sediment becomes sedimentary rock Step 3: Fossil dissolves out of rock leaving a mold (hollow depression in rock) Step 4: Minerals eventually fill the opening leaving a cast (copy of original fossil) Ex. Shells, Ferns, Leaves, and Fish
Formation of fossils Trace Fossils What do you think these are? • Indirect evidence of an organisms existence. • Ex. Footprints, impression in rocks, tracks, burrows or bite marks
Formation of fossils Carbonaceous films What do you think these are? • Thin film resembling a silhouette. • Organism remains subject to high temp and pressure undergo chemical change leaving only a thin film.