A Trip Through Geologic Time

1. A Trip Through Geologic Time

2. Earth’s History Geological Time Scale: Eras, Periods Major Geologic Events Rocks and The Fossil Record

3. Preassessment What is Geological Time? Name two scales of Geological Time What is the Principle of Superposition? List the Eras of the Geologic Time Scale List 3 to 5 Periods of the Geologic Time Scale

4. Cenozoic Era “Age of the Mammals” Today to 65 million years ago Continents drifted farther apart Quaternary “The Age of Man” and Tertiary Period Homo sapiens, flowers, birds appeared Extinction of dinosaurs

5. Mesozoic Era “Age of the Reptiles” 65 to 248 million years ago Cretaceous, Jurassic, and Triassic Periods Dinosaurs appeared and ruled First mammals appeared Started as desolate time(90% of Earth’s species became extinct)

6. “Pangaea” Tectonic forces split Pangaea into two- Laurasia in the north and Gondwana in the south Closed the same way it began- mass extinction, meteorite or volcanic activity

7. Paleozoic Era 248 to 540 million years ago Permian “Age of Amphibians”, Carboniferous, Devonian “Age of Fishes”, Silurian, Ordovician, Cambrian First reptiles appear Trees appear First amphibians appear Earliest fish appear Oxygen attains 20 percent level

8. Precambrian Era 540 million to 4.6 billion years ago Origin of the Earth First cells appear (no nucleus) Period of no free oxygen Cyanobacteria (no nucleus) produce oxygen Oxygen accumulates; cells evolve to use it Complex cells (with nucleus) appear

9. Advanced complex cells (with nucleus) appear Multi-cellular plants and animals appear Marine invertebrates appear (sponges, mollusks, arthropods) http://www.arkive.org/invertebrates-marine/ Earliest fish appear

10. What is Time? Difference between human time and geologic time Geologic Time: the time of the physical formation and development of the earth

11. Two Scales of Geologic Time Relative Time: the sequencing of events, the order in which things happened. Doesn’t describe exactly when something happened, rather what happened before and after. Example (Trilobite, Stegosaurus, Wolley Mammoth) Absolute Time: the actual time an event happened. Example (Our Earth is 4.6 billion years old)

12. Fossils • Fossils are preserved remains or traces of living things. • Most fossils form when living things die and are buried by sediments. • The sediments slowly harden into rock and preserve the shape of the organisms. • Scientists who study fossils are paleontologists.

13. Fossils • Fossils are usually found in sedimentary rocks. • When an organism dies, its soft parts often decay quickly leaving only the hard parts to fossilize. • Ex. Bones, Shells, Teeth, or Seeds

14. Kinds of Fossils • Petrified Fossils: fossils in which minerals replace all or part of the organism. Ex: petrified wood • When the object is buried by sediment, water rich in minerals seeps into the cells. After the water evaporates, hardened minerals are left behind.

15. Kinds of Fossils • Molds and Casts • A mold is a hollow area in sediment in the shape of an organism or part of an organism. • A cast is a copy of the shape of an organism.

16. Kinds of Fossils • Carbon Films: an extremely thin coating of carbon on rock that forms when materials that make up an organism become gases and escape leaving only carbon behind. • Trace Fossils provide evidence of the activities of ancient organisms. Ex: footprints, animal trails, or animal burrows.

17. Kinds of Fossils • Preserved Remains are formed when an organism is preserved with little or no change. • For example when organisms become preserved in tar, amber (tree sap), and freezing.

18. Why Study Fossils? • Scientists study fossils to learn what past life forms were like. • Paleontologists classify organisms in the order in which they lived. • All the information scientists have gathered is called the fossil record.

19. Fossil Record • The fossil record provides evidence about the history of life on Earth. • The fossil record also shows how different groups of organisms have changed over time. • It also provides evidence to support the theory of evolution.

20. Remember! • A scientific theory is a well-tested concept that explains a wide range of observations. • The fossil record shows that millions of types of organisms have evolved. • However, many others became extinct.

21. Finding the Age of Rocks Through Rock Dating

22. D A T I N G R O C K

23. Ages of Rocks • The relative age of a rock is its age compared to other rocks. Use words like: “older or younger” • The absolute age of a rock is the number of years since the rock was formed. Ex: 358-360 mya

24. Rock Joke!! • What does a rock want to be when it grows up? • A Rock Star!!

25. The Position of Rock Layers • It can be difficult to determine a rocks absolute age. So… scientists use the Principle of Superposition. • According to the Principle of Superposition, in horizontal sedimentary rock layers the oldest layer is at the bottom. Each higher layer is younger than the layers below it.

26. Rock Joke!! • How do rocks wash their clothes? • The Rock Cycle!!

27. Other Clues to Relative Age • Clues From Igneous Rock • Lava that cools at the surface is called an extrusion. Rock below an extrusion is always older. • Magma that cools beneath the surface is called an intrusion. An intrusion is always younger than the rock layers around and beneath it.

28. Other Clues to Relative Age • Faults (a break in the rock) are always younger than the rock it cuts through! • Unconformities: An unconformity is a gap in the geological record that can occur when erosion wears away rock layers and other rock layers form on top of the eroded surface.

29. Using Fossils to Date Rocks! • Scientists use index fossils to match rock layers. • An index fossil must be widely distributed and represent a type of organism that existed only briefly. • They are useful because they tell the relative ages of the rock layers they are found in.

30. The Trilobite • One example of an index fossil is a trilobite. • Trilobites were a group of hard-shelled animals whose bodies had three distinct parts. • They evolved in shallow seas more than 500 million years ago.

31. Theory of Natural Selection Developed by Charles Darwin, biologist from England Studied various species of living things Theory which states that species that are best adapted to their environment are more likely to survive and pass on their traits. “Survival of the Fittest” This supports his Theory of Evolution which is all forms of life have arisen from earlier forms of life

32. http://listverse.com/2011/11/19/8-examples-of-evolution-in-action/http://listverse.com/2011/11/19/8-examples-of-evolution-in-action/