Transcript Slide 1
Notes SPI 0807.5.5 Fossils DEC 2012 What Are Fossils? PRESS THE RIGHT-ARROW The preserved physicalON remains ofKEYBOARD deceased organisms that BUTTON YOUR are at least 10,000 years old STARTED! TO GET 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 Made 8 Types of Fossils A) Fossils In Rocks E) Frozen Fossils B) Fossils In Amber F) Trace Fossils C) Petrified Fossils D) Fossils In Asphalt G) Mold/Cast Fossils H) Index Fossils 1 Notes SPI 0807.5.5 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 0807.5.5 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 1 Notes SPI 0807.5.5 Fossils Science C) Petrified Fossils (Also known as petrifaction) Organism died- then was covered with mud, dirt, sand, ash, etc. The structure of the organism was replaced with minerals 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. Example: Petrified Wood Example: Petrified Wood 1 Notes SPI 0807.5.5 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) 1 Notes SPI 0807.5.5 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. 42,000 yrs old Frozen Baby Mammoth (From Siberia, Russia) Approx: 40, 000 yrs old 1 Notes SPI 0807.5.5 Fossils Science F) Trace Fossils (Also called ichnofossils) 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 Dinosaur footprints Trace Fossil Imprint Of A Fish 1 Notes SPI 0807.5.5 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 0807.5.5 Fossils Science H) Index Fossils A way to relatively date rocks (A.K.A. relative dating) Some fossils are commonly found at certain strata levels across large geographic areas …we call these index fossils Example: Ammonite fossils Example: Trilobite fossils 1 SPI 0807.5.5 Fossils Notes Science Sedimentary rock and fossils …called the law of superposition 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. B is older than A So fossils inSo deeper older fossils fossillayers one is are older thanthan fossil two above it. 3 2 Layer A Layer B 1 Layer C 1