Geological Changes Yellow is the magic color 8th Grade Science Riverwood Middle Clayton, NC
8.E.2 Understand the history of Earth and its life forms based on evidence of change recorded in fossil records and landforms. • 8.E.2.1 Infer the age of Earth and relative age of rocks and fossils from index fossils and ordering of rock layers (relative dating and • radioactive dating). • 8.E.2.2 Explain the use of fossils, ice cores, composition of sedimentary rocks, faults, and igneous rock formations found in rock layers as evidence of the history of the Earth and its changing life forms.
Vocabulary 1. Fossil 2. Mold 3. Cast 4. Petrified 5. Preserved 6. Carbonized 7. Trace 8. Sedimentary rock 9. Paleontologist 10. Extinct 11. Relative age 12. Absolute age 13. Law of superposition 14. Extrusion 15. Intrusion 16. Fault 17. Unconformity 18. Index fossil 19. Radioactive decay 20. half-life 21. Geologic time scale 22. Era 23. Period 24. Continental drift • Pre-Test • Vocabulary • Field Guide Book • Pangaea and Continental Drift Worksheet • Video: Continents Adrift: An Introduction to Continental Drift and Plate Tectonics 26:05
What can we know about Earth’s present and future by finding out about its past?
How old is Earth? How can we determine Earth’s age? Where is the evidence?
The Earth is 4.54 billion years old. 1 billion seconds equals 1,000,000,000 16666666.7 minutes277777.8 hours11574.1 days1653.4 weeks308.3 months31.7 years
Has Earth Changed Over Time? What is the evidence?
Pangaea • Formed about 260 million years ago during the Permian Period. • Earth’s continents moved together to form a great landmass, or supercontinent. • This caused deserts to expand to the tropics and sheets of ice covered land closer to the South Pole. • Many organisms could not survive the new climates.
Pangaea • Pangaea holds together for much of the Triassic period where hot, dry conditions dominate the center of Pangaea. • Pangaea broke apart during the Jurassic period as North America separated from Africa and South America.
Evidence that Support Theory of Continental Drift • Puzzle-shaped continent pieces fit together • Rock layer similarities • Fossil find similarities • Ring of Fire – Pacific ocean compressing • Measurement – Atlantic Ocean widening Ring of Fire
Law of Superposition • On your desk, you have 8 index cards with nonsense letters placed on them. • Your task is to determine what the correct sequence of the letters are. • Hint: The “oldest” card is TAR
Eel • Toe • Mat • Emma • Gem • Dog • Red • Tar
What does the order of rock layers tell us about • Earth’s past? 2. What’s the name of that Law?
What does the order of rock layers tell us about Earth’s past? The lowest rocks are the oldest What’s the name of that Law? The Law of Superposition
Law of Superposition • States that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks.
Law of Superposition Examples • Laundry basket • Locker • Making a Sandwich • BozmanVideo: https://www.youtube.com/watch?v=EadTLGMu3LI
Unconformities • 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.
Other Clues to Relative Age • Magma that cools beneath the surface is called an intrusion • An intrusion is always younger than the rock layers around and beneath it
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.
Forms an actual rock layer Shoves itself into the existing rock layers
Clues to Relative Age The Cross-Cutting Law • Faults (a break in the rock) are always younger than the rock it cuts through! • Fractures (a crack in the rock) are always younger than the rock it cuts through • Faults and Fractures are younger than the rocks they cut through.
Faults are fractures in Earth's crust where rocks on either side of the crack have slid past each other.
Faults • There are three kinds of faults: strike-slip, normal and reverse faults. Each type is the outcome of different forces pushing or pulling on the crust, causing rocks to slide up, down or past each other.
Mountain Building animation – 20 seconds each – http://www.youtube.com/watch?v=loFxYSHxTf0 http://www.youtube.com/watch?v=Tzt_EBD3DDQ
E YOUNGEST _______ _______ _______ _______ OLDEST _______ D A B C
YOUNGEST ____A___ ____D___ ____B___ OLDEST ___C____ YOUNGEST ___E____ ___D____ ___C____ ___A____ OLDEST ___B____ A - sand B – brick C – lava D – Crack E – break
Physical Evidence Supports the Theory of Geologic Change This land was once the ocean floor. It’s location is above a compression plate boundary Fossils of sea creatures found at the summit As the plate push together the mountain gets higher Mt. Everest
Finding Clues to Rock Layers – Skills Lab NCPH p 330 NC 8.E.2.1 Infer the age of Earth and relative age of rocks and fossils from index fossils and ordering of rock layers.
More… Change over time
A Date with the Fossil Record Task: A paleontologist from Utah has sent you 9 samples from a series of rock layers. She needs your help in determining the relative age of the fossils. Another lab is using radioactive dating to determine the absolute age of the fossils and the results will not be available for several weeks. The paleontologist needs your information immediately. ***You know from previous work that the rocks of Sample 2 are the oldest*** Materials: nine cards representing the rock samples, pencil, fossil key & fossil date card Procedure: Determining Relative Age Step One: Carefully study the cards and the fossil key you have been given. Beginning with Sample 2, arrange the fossil cards from oldest to youngest. If needed, try different arrangements until you get them in order. Remember: After an organism becomes extinct, it does not reappear in younger rocks.
A Date with the Fossil Record Step Two: After the cards are arranged in the correct order, complete the following data table by recording the samples in order from bottom to top (oldest to youngest) in the first column. The information for Sample 2 has been done for you. Use the fossil to identify the fossils and write their names in order by age from left to right (oldest to youngest) in the top row of the table. Beside each sample, write an X in the appropriate column to indicate which fossil(s) are present in each sample.