FOSSILS
help geologists study Earth’s past & determine… Fossils help geologists study Earth’s past & determine… Approximately when life began What plants & animals were 1st to live on land When organisms appeared/disappeared How organisms live
Fossils Can be in the form of: REMAINS IMPRINTS BONES TEETH TRACES
How Fossils form The body must be protected from scavengers & bacteria Hard parts have a better chance of becoming fossils Fossils are found in sedimentary rocks
Types of Fossils Original remains Petrified remains Molds/Casts Trace fossils Carbonaceous film
Original Remains An actual organism or part of an organism Usually forms in amber or ice – must be preserved quickly
Carbon residue left by an organism Carbonaceous Film Carbon residue left by an organism Coal is a carbon residue left by millions of organisms together – a fossil fuel!
Replaced or Petrified remains Some or all of the original material has been replaced by minerals, such as when silica seeps into buried trees & creates a replica of the tree called petrified wood
Molds & Casts Impressions of an organism left in clay, sand or mud Mold: organism decays inside rock, leaving a cavity that is an impression of the outside Cast: mold fills in with sediments, making a replica of the organism Watch them form! Cast Mold
Trace Fossils Fossilized tracks, tools, burrows or other traces left of ancient organisms
INDEX FOSSILS Since each organism comes from a specific time period, we can use a fossil to determine the age of the rock it is found in. The shorter the time a certain organism lived, the better we know when the rock formed. These special fossils are called index fossils.
Index Fossils - Requirements Existing for a short period of time Abundant over a wide area So it is more useful for comparing rocks in different places http://seedmagazine.com/content/article/the_evolution_of_life_in_60_seconds/ http://www.johnkyrk.com/evolution.html
Which of the following do you think is most likely to preserve a fossil safely, & why?
State Fossils Delaware: Belemnitella americana Virginia: Chesapecten jeffersonius Maryland: Ecphora gardnerae
Bibliography http://wrgis.wr.usgs.gov/docs/parks/gtime/ http://www.cr.nps.gov/museum/exhibits/dino/geotime/geotime2.html http://denali.gsfc.nasa.gov/sci_hi/sci_hi_2004_05/2004_05b.html http://maritime.haifa.ac.il/departm/lessons/ocean/lect03.htm http://www2.worldbook.com/wc/popup?path=features/dinosaurs&page=html/trilobite.htm&direct=yes http://www.intelligentdesign.org/menu/evolution/fossils/fishes.htm http://www2.worldbook.com/wc/popup?path=features/dinosaurs&page=html/mesozoic.htm&direct=yes http://skullduggery.com/extinct.htm http://www.lpi.usra.edu/education/timeline/gallery/images/063.jpg http://library.thinkquest.org/11922/extinct/mammoth.htm http://www.hmag.gla.ac.uk/Neil/Amber/ant.jpg http://www.paleozoic.org/shows/tucson-2003/images/fs/petrified-stumps.jpg http://www.gpc.edu/~pgore/myphotos/fossils/cast&mold.jpg http://www.baystatereplicas.com/images/dino_multi_tracks2.jpg http://www.humboldt.edu/~natmus/Case_indexes/Case_jpgs/MakeFossil.web/368.jpg http://upload.wikimedia.org/wikipedia/commons/a/a5/Conglomerate_Death_Valley_NP.jpg http://www.es.ucl.ac.uk/schools/Glossary/sandstone.jpg http://www.geology.wisc.edu/courses/g112/Images/gneiss2.jpg