1. Fossils

2. Fossils Remains or evidence of those organisms in layers of rock are called fossils. Remains or evidence of those organisms in layers of rock are called fossils. Most fossils form in sedimentary rock.The hard parts (bones, shells, teeth) of a living thing are surrounded by sediments that collect on the floor of a body of water. These hard parts become trapped as the sediments harden into rock. Most fossils form in sedimentary rock.The hard parts (bones, shells, teeth) of a living thing are surrounded by sediments that collect on the floor of a body of water. These hard parts become trapped as the sediments harden into rock. Fossils are found in sedimentary rock Fossils are found in sedimentary rock Recall sediment is the material removed by erosion. Sediment is made up of rock particles or the remains of living things. Recall sediment is the material removed by erosion. Sediment is made up of rock particles or the remains of living things. Other kinds of fossils form when both hard parts and soft parts of living things are buried in layers of ice or trapped in tree sap that later hardens Other kinds of fossils form when both hard parts and soft parts of living things are buried in layers of ice or trapped in tree sap that later hardens

3. Fossils Fossils found in rock include mold and casts, petrified fossils, carbon films, and trace fossils. Other fossils form when the remains of organisms are preserved in substances such as tar,amber, or ice. Fossils found in rock include mold and casts, petrified fossils, carbon films, and trace fossils. Other fossils form when the remains of organisms are preserved in substances such as tar,amber, or ice.

4. Petrified Fossil Are Fossils in which minerals replace all or part of an organism. Are Fossils in which minerals replace all or part of an organism. Example: Petrified tree trunk Example: Petrified tree trunk

5. Trace Fossil Include the footprints, track, trails, and burrows made by living things. Include the footprints, track, trails, and burrows made by living things. Example: Dinosaur footprint. The mud or sand that the animal stepped in was buried by layers of sediments. Slowly the sediment became solid rock, preserving the footprint for millions of years. Example: Dinosaur footprint. The mud or sand that the animal stepped in was buried by layers of sediments. Slowly the sediment became solid rock, preserving the footprint for millions of years.

6. Cast and Mold Cast is a model in the shape of a living thing or its remains. A cast forms when minerals or rock particles fill the space in a mold. Cast is a model in the shape of a living thing or its remains. A cast forms when minerals or rock particles fill the space in a mold. Mold is a space in a rock that has the shape of the remains of a living thing that once occupied that space. Mold is a space in a rock that has the shape of the remains of a living thing that once occupied that space.

7. Carbon Film Remember all living things contain carbon. When sediment buries an organism, some materials that make up the organism evaporate or become gases. These gases escape from the sediment, leaving carbon behind. Only a thin film of carbon remains. Remember all living things contain carbon. When sediment buries an organism, some materials that make up the organism evaporate or become gases. These gases escape from the sediment, leaving carbon behind. Only a thin film of carbon remains. Example: Delicate parts of plants and insects. Example: Delicate parts of plants and insects.

8. Fossil Records Fossil records provides evidence about the history of life and past environments on Earth. The fossil record also shows that different groups of organisms have changed over time. Fossil records provides evidence about the history of life and past environments on Earth. The fossil record also shows that different groups of organisms have changed over time. Paleontologist are scientist who study fossils. Paleontologist are scientist who study fossils. Fossils build up a picture of Earth’s past environments. It also provides evidence of a past climate of a region. Example, coal was found in Antarctica. But coal only forms from the remains of plants that grow in warm swampy regions. The presence of coal shows that the climate in Antarctica was once much warmer than it is today. Fossils build up a picture of Earth’s past environments. It also provides evidence of a past climate of a region. Example, coal was found in Antarctica. But coal only forms from the remains of plants that grow in warm swampy regions. The presence of coal shows that the climate in Antarctica was once much warmer than it is today.

9. Fossil Records Fossil records provide evidence to support the theory of evolution. Fossil records provide evidence to support the theory of evolution. Evolution is the gradual change in living things over a long period of time. Evolution is the gradual change in living things over a long period of time.

10. Radioactive Decay Rocks are a form of matter. All matter contains atoms. When all the atoms in a particular type of matter are the same, the matter is an element. Rocks are a form of matter. All matter contains atoms. When all the atoms in a particular type of matter are the same, the matter is an element. Most elements are stable. They do not change under normal circumstances. But some elements exists in forms that are unstable. These elements break down or decays, by releasing particles and energy in a process called radioactive decay. Most elements are stable. They do not change under normal circumstances. But some elements exists in forms that are unstable. These elements break down or decays, by releasing particles and energy in a process called radioactive decay. During the radioactive decay, the atoms of one element break down to form atoms of another element. During the radioactive decay, the atoms of one element break down to form atoms of another element. The rate of decay of each radioactive element is constant-it never changes. This rate of decay is the elements half- life. The half – life of radioactive element is the time it takes for half of the radioactive element to decay. The rate of decay of each radioactive element is constant-it never changes. This rate of decay is the elements half- life. The half – life of radioactive element is the time it takes for half of the radioactive element to decay. Geologist use radioactive dating to determine the absolute age of the rocks. Geologist use radioactive dating to determine the absolute age of the rocks. Radioactive dating works well with igneous rocks but not for sedimentary rocks. The rock particles in sedimentary rocks are from other rocks, all of Radioactive dating works well with igneous rocks but not for sedimentary rocks. The rock particles in sedimentary rocks are from other rocks, all of different ages. different ages. How do scientists date sedimentary rock layers? They date the igneous intrusions and extrusions near the sedimentary rock.