8 th Grade Science Final

1. 8th Grade Science Final Study Guide Review

2. I. Earth’s Layers • What are Earth’s Layers? inner core, outer core, mantle and crust • Which layer is the thickest? the mantle • Which layers make up the tectonic plates? lithosphere – all of the crust and the upper mantle

3. II. Earth’s History 4. Who is Wegner? The scientist who first came up with the idea that the continents move, there was once a super continent, Pangaea 5. Tell what supports his theory of continental drift Climate, similar rocks and fossils on different continents

4. III. Boundaries/Tectonic Plates 6. Where is the crust oldest? How does this support spreading centers? Boundary? Older crusts will be found away from the center, usually at trenches (convergent boundaries). Younger rock at a ridge (divergent boundaries) 7. Convection currents in the asthenosphere? As the hot molten rock moves in a current in the asthenosphere it moves the plates in the direction of the current

5. 8. What is going on with the magnetic minerals at the mid ocean ridges? The minerals point in the same direction, right now they are pointing north, over time they will change direction. The pattern is the same on either side of the ridge

6. 9. Convergent Boundaries • Colliding   • Oceanic-Oceanic – two oceanic plates, the older colder plate slides under the younger plate – deep ocean trenches and volcanic islands are formed • Oceanic-Continental – the oceanic plate is denser so it slides under the continental plate – deep ocean trenches and coastal volcanic mountains are formed • Continental-Continental- continental crust pushes together and mountains are formed

7. 10. Divergent Boundaries Plates are separating   On the ocean floor mid ocean ridges will be formed. When continents separate a great rift valley will be formed

8. 11. Transform boundaries Plates scrape past one another. When a lot of stress builds up an earthquake will occur

9. IV. Earthquakes 12. What is an earthquake? The release of stress built up due to the sudden and quick movement of rocks along a fault 13. What determines the strength of an earthquake? How deep the focus is and how far the blocks of rocks move

10. 14. Normal fault Blocks of rock slide down as they pull apart Divergent boundaries 15. Reverse fault Blocks of rocks slide up as they push against each other Convergent boundaries 16 strike-slip fault Blocks of rocks slide past each other Transform boundaries

11. 17.How many seismograms? Why? THREE seismograms are needed, where they intersect is the epicenter of the earthquake 18. Difference between focus and epicenter Epicenter is on earth’s surface which is located directly above the focus. The focus is the actual spot that the earthquake occured

12. 19. Primary waves, secondary waves, surface waves Primary waves- p-waves, move the fastest, push pull, 1st to arrive at the seismograph station, can travel through solid, liquid and gas Secondary waves – s-waves, slower, move side to side, second to arrive, can travel through solids Surface waves – move on the surface, cause the most damage 20. Earthquake resistant buildings Adding cross braces, moat and shear wall

13. V. Blocks of Rocks 21. Folded mountains Occur at ancient boundaries when two continental plates have collided 22. What causes blocks of rocks to tilt along faults? Spreading centers – like along the ocean floor

14. VI. Volcanoes 23. Volcanoes It is an opening through which lava, rocks and gas erupt. Happen at convergent and divergent boundaries and hot spots. Three types – cinder cone, composite and shield 24. Pyroclastic flow The combination of very fast moving extremely hot gases and rocks

15. 25. What are the signs that a volcano may erupt soon Rising temperatures of local bodies of water, increase gases, movement of rocks 26. Effects of a volcano Effects: ash, lava, pyroclastic flow, rocks, landslides, mudslides Most dangerous: ash – ash clouds Atmosphere: increased acid rain and a decrease in temperature

16. VII. Rocks 27.Three types of rocks? contain/not contain fossils Sedimentary – different types of rocks, most likely to contain fossils Igneous – cooled molten rock, will not contain fossils, will destroy fossils because of the high temperature Metamorphic – changing rock 28. Original remains/rock fossil Original remains will be found in amber (sap of a plant Rock fossils are mold and casts

17. 29. Rock layers The youngest rock layer will be at the top, igneous rock will be younger than the layers of sediment it cuts through 30. Uniformitarianism Earth is constantly changing and the same forces that changes it in the past are changing it today 31. Relative age/absolute age Relative age – how the age relates to something else, age of the layers of sedimentary rock is determined this way Absolute age – exact age based on facts, like your age based on your birthdate

18. VII. Genetics and Heredity 32. What determines the genetic code? The sequence of bases in a strand of DNA 33. What is the code for making RNA and protein? DNA 34. Where do you inherit your genes from? Your parents

19. 35. What is a genotype? Example The traits that are passed down, includes both alleles BB, Bb, bb 36. What is a phenotype? Example The traits that are visible, how the alleles combine, includes eye color, hair color, earlobes 37. What are alleles? Various forms of the same gene

20. 38. What is the difference between dominant and recessive genes? Dominant is the gene that will show through when paired with another dominant or a recessive gene DD Dd Recessive will only show when paired with another recessive gene dd

21. 39. What is a Punnett Square? Ratio/percent A diagram that will show the probability of the traits of an offspring T T t 100% chance of genotype Tt t 40. What is fertilization? The process that takes place when a sperm combines with an egg Tt Tt Tt Tt