Download Fossilization

Journal #1 - Fossils
1.
What is a fossil?
2.
How do fossils help geologists learn
information about the past?
3.
What type of rock are fossils found in?
Fossils
Objective: Understanding different fossil
formation and how they are a key to past
geologic events.
Fossils
 Fossils
◦ Preserved in rocks
◦ Only a small portion of organisms
◦ Help support theories of different life
◦ Tell us where, when and how organism
lived
Fossils
 Creation
of Fossils
◦ Organism CANNOT decay
◦ Buried quickly (mudflow, tar pit)
◦ Hard parts (bones, teeth, exoskeleton)
Fossil Evidence

Evolution
◦ Similarity of fossils in different time periods
◦ Old Rocks  Fish;Young Rocks  Amphibians

Past Environments
◦ Show changes in Earth
◦ Water habitats show up in rock layers now above
sea level
Different Types of Fossils
 Fossilization
– process of creating a fossil
 Types
◦ Petrified
◦ Carbonaceous Film
◦ Mold and Cast
◦ Amber
◦ Tar Pits
◦ Frozen in the Ground
◦ Trace Fossils
Petrified
 Petrified
Fossils
◦ Some or all of the original materials
in the remains have been replaced
by minerals
Carbonaceous Film
 Carbon
Fossils
◦ Organism is buried by sediments that pile
up and increase heat and pressure
◦ Gases and liquids forced from the body
◦ Thin film of carbon residue is left forming
an outline
Mold and Cast

Mold and Cast Fossils
◦ Organism is buried
◦ Fossil weathers and erodes from water moving
through pores in the rock layers
◦ Harder rock surrounding fossil forms a mold
◦ Sediments are carried into the mold and deposited
◦ A cast is created
Amber
 Amber
Fossils
◦ Organisms are trapped in liquid amber
◦ Amber hardens, preserves organism
inside
Tar Pits
 Tar
Pit Fossils
◦ Organisms get trapped in tar pits
Frozen Fossils
 Frozen
in Ice
◦ Organisms that get trapped in a
decrease in temperature
◦ Organisms preserved in chunks of ice
Trace Fossils
 Trace
Fossils
◦ Show an organisms movement
 Size, weight, age
 Speed of movement
 Lifestyle
 Social life
Index Fossils
 Index
Fossils
◦ Used to date rock layers