1. Begin Earth’s Past 3/28/12 What do you know about Fossils?

2. Fossils are traces or remnants of past life. Many fossils are found in rock. Rocks, fossils, and other natural evidence provide information about how Earth and life on Earth have changed over time.

4. original remains A fossil that is the actual body or body parts of an organism. The are 3 different substances original remains are found are the following: 1.1. Ice- Ice preserves remains (Mammoth) 2.2. Amber- Resin from tree hardened and preserves remains (insects) 3.3.Tar- Pools of tar preserve remains (Saber- toothed cats)

8. Fossils in Rocks These fossils are impressions or traces made of rock and provide indirect evidence that the organisms were there. There are 4 types of fossils in rocks: 1.Mold and Cast 2.Petrified wood 3.Carbon Films 4.Trace fossils

9. Process and Example of Mold and Cast 1. Organism dies and falls into soft sediment. 2. Over time, the sediment becomes rock and the organism decays, leaving a mold. 3. Minerals fill the mold and make a cast of the organism. Example- Clams, snails

11. A mold and cast fossil is formed when minerals take the shape of a decayed organism.

12. Petrified Wood The stone fossil of a tree is called petrified wood. Process - A fallen tree an be covered with sediment. Over time, water passes through the sediments and into the trees cells. Minerals that are carried in the water take the place of the cells, producing a stone likeness of the tree. Example- petrified forest

13. Petrified Wood

14. Carbon Films Carbon is an element that is found in everything living. Process- Sometimes when dead plant or animal decays, its carbon is left behind on a visible layer. Example- moth 10 million years old

15. Carbon Films

16. Trace Fossils Example of Trace fossils include preserved footprints, trails, animal holes, and even feces. Process of how the trace fossils are preserved is when weather changes drastically and causes weathering and erosion to occur which preserves events that occurred prior to the change.

17. Trace Fossils

18. Relative Age Scientists combine information about the relative and absolute ages of rocks and fossils to construct a timeline of Earth.

19. relative age The age of an event or object in relation to other events or objects.

20. index fossil A fossil of an organism that was common, lived in many areas, and existed only during a certain span of time. Index fossils are used to help determine the age of rock layers.

21. absolute age The actual age in years of an event or object.

22. half-life The length of time it takes for half of the atoms in a sample of a radioactive element to decay into atoms of another element

27. Sedimentary rock layers show the order in which rocks formed. The order of the layers is used to determine the relative ages of fossils found in the rock. Radioactive dating can be used to determine the absolute age of igneous rock.