Notes

1. SPI 0807.5.5 Fossils Notes 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 Made PRESS THE RIGHT-ARROW BUTTON ON YOUR KEYBOARD TO GET STARTED!  1

2. SPI 0807.5.5 Fossils Notes 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 2

3. SPI 0807.5.5 Fossils Notes 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 3

4. SPI 0807.5.5 Fossils Notes Science (Also known as petrifaction) • C) Petrified Fossils • 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 4

5. SPI 0807.5.5 Fossils Notes 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) 5

6. SPI 0807.5.5 Fossils Notes 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 6

7. SPI 0807.5.5 Fossils Notes 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. (Also called ichnofossils) Trace Fossil Imprint Of A Fish Trace Fossil Dinosaur footprints 7

8. SPI 0807.5.5 Fossils Notes 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 Cast Fossil Mold Fossil 1

9. SPI 0807.5.5 Fossils Notes 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: Trilobite fossils Example: Ammonite fossils 9

10. SPI 0807.5.5 Fossils Notes 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. …called the law of superposition B is older than A So fossil one is older than fossil two 3 Layer A 2 Layer B 1 Layer C 10