trace fossil carbon film petrified wood brachiopod mold insects in amber Types of Fossils There are a number of ways that fossils form. Fossils found in limestone are usually formed by a process called cast and mold. Petrified wood is formed by a process called petrification. The original wood fibers are slowly and completely replaced by mineral material, usually quartz (agate). Plant leaves and stems have been preserved by a process called carbonization. During this process the leaves and stems deteriorate but leave a film of carbon which preserves their form. Flies, dragonflies and other insects have been preserved in amber. Amber is hardened tree sap. Trace fossils, such as a preserved footprint, provide evidence of the activities and body characteristics of an ancient organism. wooly mammoth saber tooth tiger giant sloth How a Fossil Forms Fossils and Past Environments Fossils reveal information about past ecosystems, the variety of life forms in those ecosystems, the relationships of the organisms and more. Scientists who specialize in the fossilized remains of ancient life forms are called paleontologists. Collections of fossils from a particular rock formation give information about the environment in which the organisms lived. Fossils can help scientists understand ancient environmental factors such as temperature. Quite often fossils are strong evidence supporting the theory of plate tectonics and continental drift. What Is a Fossil? A fossil is any naturally preserved evidence of life which existed long ago. Fossils include pieces or the entire remains of organisms called body fossils. Fossils also include traces and marks left by organisms, such as footprints, called trace fossils. Most fossils form from organisms that once lived near bodies of water, such as ponds, lakes and shallow seas. Phase 1 – Death After an organism dies, it slowly sinks to the sea floor. Phase 2 – Deposition The skeleton gradually becomes covered with silt and sand (sediment). Phase 3 – Petrification Over millions of years the original skeleton becomes petrified (rock-like). Phase 4 – Erosion Millions of years later, the movement of the Earth’s plates forces the seabed to move above the surface. This layer is worn away by wind and rain, exposing the fossil. Some photos courtesy of USGS and NPS. © Copyright NewPath Learning. All Rights Reserved. 94-4103 www.newpathlearning.com Fossils
Types of Fossils Describe the following: Cast and mold: ____________________________________________________________ _________________________________________________________________________ Petrification: _____________________________________________________________ _________________________________________________________________________ Carbonization: ____________________________________________________________ _________________________________________________________________________ Amber: __________________________________________________________________ _________________________________________________________________________ Trace fossils: ______________________________________________________________ _________________________________________________________________________ wooly mammoth saber tooth tiger giant sloth How a Fossil Forms Fossils and Past Environments Describe the information that can be revealed about past environments from fossils. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ What Is a Fossil? _____________________________________ _____________________________________ _____________________________________ _____________________________________ Most fossils form from organisms that once lived near bodies of water, such as ponds, lakes and shallow seas. Phase 1 – _____________________ Describe: __________________________ ___________________________________ Phase 3 – _____________________ Describe: __________________________ ___________________________________ Phase 4 – _____________________ Describe: __________________________ ___________________________________ ___________________________________ Key Vocabulary Terms • amber • body fossil • carbon film • carbonization • cast and mold • deposition • erosion • fossil • paleontologists • petrification • trace fossil Phase 2 – _____________________ Describe: __________________________ ___________________________________ © Copyright NewPath Learning. All Rights Reserved. 94-4103 www.newpathlearning.com Fossils Some photos courtesy of USGS and NPS.
