12/10/2012 1 Chapter 29: Studying the Past Fossils • Paleontology : the study of the life that existed in prehistoric times • Fossils form in several ways – Original remains – Replaced remains – Molds and casts – Trace fossils – Carbonaceous films • Original remains – Full body is preserved completely Mosquito trapped in resin (amber) Baby wooly mammoth preserved in permafrost (Siberia) • Replaced remains – Plants and animals parts are replaced slowly by rock-forming minerals T-Rex… Rawr! Petrified wood… used to be plant material, now it’s all minerals • Petrified National Forest, Arizona • Molds and casts – Mold : A hollow depression in rock formed when a fossil dissolved out of the rock; shows the original shape and surface of the fossil Trilobite mold and cast. It’s the Wisconsin State Fossil!
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Transcript
12/10/2012
1
Chapter 29: Studying the Past Fossils
• Paleontology: the study of the life that existed in prehistoric times
• Fossils form in several ways
– Original remains
– Replaced remains
– Molds and casts
– Trace fossils
– Carbonaceous films
• Original remains
– Full body is preserved completely
Mosquito trapped in resin (amber) Baby wooly mammoth preserved in permafrost (Siberia)
• Replaced remains
– Plants and animals parts are replaced slowly by rock-forming minerals
T-Rex… Rawr! Petrified wood… used to be plant material, now it’s all minerals
• Petrified National Forest, Arizona • Molds and casts
– Mold: A hollow depression in rock formed when a fossil dissolved out of the rock; shows the original shape and surface of the fossil
Trilobite mold and cast. It’s the Wisconsin State Fossil!
12/10/2012
2
• Molds and casts
– Cast: An object created when minerals seep into and fill a mold, forming a copy of the original fossil
Trilobite mold and cast. It’s the Wisconsin State Fossil!
• Trace Fossils
– Any indirect evidence of life preserved as an impression in rock; trails, footprints, tracks,
burrows, and bite marks
Worm trailClaw prints
• Carbonaceous film
– A thin carbon film resembling a silhouette caused by high temperature & pressure