1 Notes SPI Fossils DEC 2012 What Are Fossils?  The preserved physical remains of deceased organisms that are at least 10,000 years old  NOTE: Most organisms do not become fossils when they die  NOTE: The formation of fossils is a rare event How Are Fossils Formed?  Watch this amusing video: Link: Video: How Fossils Are MadeVideo: How Fossils Are Made PRESS THE RIGHT-ARROW BUTTON ON YOUR KEYBOARD TO GET STARTED! 8 Types of Fossils A) Fossils In RocksE) Frozen Fossils B) Fossils In AmberF) Trace Fossils C) Petrified FossilsG) Mold/Cast Fossils D) Fossils In AsphaltH) Index Fossils

1 Notes SPI Fossils Science A) Fossils In Rocks  Found in sedimentary rock  An organism died – was covered with mud, dirt, sand, ash, etc.  Later the mud, dirt, sand, or ash became sedimentary rock

1 Notes SPI Fossils Science B) Fossils In Amber  Tree sap fell on a small organism, enclosed it, killed it  Over time the sap hardened into amber  The amber became covered with mud, dirt, sand, ash, etc. Example: Insects In Amber

Notes SPI Fossils Science C) Petrified Fossils  Organism died- then was covered with mud, dirt, sand, ash, etc.  The structure of the organism was replaced with minerals (Also known as petrifaction) Example: Petrified Wood 1 Example: Petrified Wood Sometimes when wood is buried, groundwater will flow through the sediment and deposit minerals in the cells of the wood. The wood rots away & the minerals remain in the shape of the tree.

1 Notes SPI Fossils Science D) Fossils In Asphalt  Animals fell into tar pits, were trapped, and died  The asphalt hardened preserving skeletons, shells, teeth, etc. Saber Tooth Tiger Fossil (From La Brea Tar Pits, California)

Notes SPI Fossils Science E) Frozen Fossils  Animals died in a cold climate region and were frozen  The cold temperatures preserved both soft and hard parts  Many mammoths became frozen during the last ice age Frozen Baby Mammoth (From Siberia, Russia) Approx: 40, 000 yrs old Frozen Baby Mammoth (From Siberia, Russia) Approx. 42,000 yrs old 1

1 Notes SPI Fossils Science F) Trace Fossils  Are impressions or “traces” left by plants and animals  Can be simple tunnels or burrows in the mud  Can be footprints or imprints in the mud etc. Trace Fossil Imprint Of A Fish (Also called ichnofossils) Trace Fossil Dinosaur footprints

1 Notes SPI Fossils Science G) Mold/Cast Fossils  In sediment, ground water may dissolve shells, leaving a shape called a mold  Sometimes the shell dissolves and is replaced by minerals, leaving behind a mineral cast of the fossil Mold Fossil Cast Fossil

1 Notes SPI Fossils Science H) Index Fossils  A way to relatively date rocks  Some fossils are commonly found at certain strata levels across large geographic areas (A.K.A. relative dating) …we call these index fossils Example: Ammonite fossils Example: Trilobite fossils

1 Notes SPI Fossils Science Sedimentary rock and fossils  deeper layers are older than layers above it. Example: See three layers below…Layer A, Layer B, and Layer C Layer C is older than layer B. So fossils in deeper layers are older than fossils above it. Layer A Layer B Layer C B is older than A …called the law of superposition So fossil one is older than fossil two