FossilsRocks and Fossils

Notes #2

What are Fossils?• Fossil- any evidence of an

organism that lived in the past.• Soft body parts like organs and

skin do not usually become fossils. They decompose easily.

• Hard parts like bones and teeth get mixed in with sediment as sedimentary rocks form.

How Old Are Fossils?• Geologists use relative

age to determine a fossil’s age.

• The deeper in the soil a fossil is found, the older it is.

Younger fossils

Olderfossils

How are Fossils Formed?• Imprint- A fossil created by a print or

impression. (ex: animal footprints.)

How are Fossils Formed?

• Mold- A fossil clearly showing the outside features of an organism.

How are Fossils Formed?

• Cast- A fossil formed, or shaped, within a mold.

MoldCast

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2901/es2901page01.cfm?chapter_no=visualization

http://petrifiedwoodmuseum.org/moldscasts.htm

How are Fossils Formed?

• Amber- Hardened tree sap, yellow to brown in color, often a source of insect fossils.

• Animals rest on trees and get trapped in the sap.amber

How are Fossils Formed?

• Petrified- When plants or animals have been preserved by being “turned to stone” by being filled by minerals.

http://www.yourgemologist.com/Kids/petrifiedwood/petrifiedwood.html

How are Fossils Formed?

These fossils were foundpreserved in tar in California.

This baby mammothwas found preservedin ice in Siberia.

http://ngm.nationalgeographic.com/2009/05/mammoths/latreille-photography

What Can We Learn From Fossils?• Fossils give us clues as to what that

environment used to be like. For example:

• Finding evergreen fossils tell a scientist that the area was once cool.

• If a fern is found in a polar region, then that region was once warm.

• What would it mean if fossils of sea creature were found on our playground?

How do we know that this dino was a carnivore?

What clues tell you that this dino was an herbivore?

Links

• every fossil tells a story