Sec 12.1 p. 506 Evidence for Continental Drift Alfred Wegener: continental drift theory Continents move around 200 mya Pangaea (pan = all, gaea= earth) fg 12.8 p. 508 Evidence: http://www.youtube.com/watch?v=rqm6n60bneo vid vid 2 -world map fig: fg 12.1 p. 506 Jigsaw puzzle Fit: continents on either sides of the oceans seem to fit together best fit underwater with continental shelves -Similar geology: mountain: ranges, folds, rock age, -Similar fossils: fg 12.4 p. 508 6000 km apart across salt water ocean? Mesosaurus (fresh water) Cynognathus & Lystsrosaurus (land animals) Glossopteris (mild climate plant fern) C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 1 of 12 Last printed 13/03/2018 1:24 PM
Climate: fg 12.5 p. 509 patterns of paleoglaciation Coal in Antarctica: formed by decomposition of living things (tropical swamp material) see science watch p. 500 Wegener: no hypothesis: How can continents move? died 1930 Possible mechanism: plate tectonics Surface of earth is broken into movable slabs of rock = rigid plates slide over partly molten rock Evidence: a) Fg 12.6 p. 510 Location of earthquakes and volcanoes pattern boundaries between tectonic plates ex: ring of fire in pacific ocean vid4 vid4 b) fg 12.7 p. 510 underwater mountain ranges: ex: Mid-Atlantic Ridge (MAR) C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 2 of 12 Last printed 13/03/2018 1:24 PM
c) age of ocean floor: fg 12.8 p. 511 changes from new on either side of Ridge to old, farther away from the Ridge vid3 d) thickness of sediment: fg 12.8 p. 511 thin near the ridge, thick away from the ridge e) magnetism: i) fg 12.9 p. 511 earth acts like a giant bar magnet (magnetic N pole, magnetic S pole) undergoes magnetic reversal every 250 000 y: (S pole N pole) ***** geographic poles: axis of rotation of the earth, do not change **** C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 3 of 12 Last printed 13/03/2018 1:24 PM
ii) paleomagnetism: fg 12.10 p. 512 study of the magnetic properties of ancient rocks magnetic striping: rock on either side of the MAR changes its magnetic field pattern as you move away from the ridge due to magnetic reversals Explanation for observations: 1960 Harry Hess: sea floor spreading Fg 12.11 p. 512 Less dense magma (liquid rock) rises at a spreading ridge and hardens forming new ocean floor earth s magnetic field magnetizes the new ocean floor as it hardens New magma keeps rising at spreading ridge Older sea floor is pushed aside by newer sea floor C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 4 of 12 Last printed 13/03/2018 1:24 PM
1960: Canadian J.Tuzo Wilson plate tectonic theory Combined the following concepts: sea floor spreading (ocean floor creation) ocean floor destruction mountain formation earthquakes volcanoes island arcs from hot spots (Hawaii) continent movements read 12.1 Wb 12.1 Sec. 12.2 Features of Plate Tectonics p. 518 4.5 billion years ago (bya): liquid earth cooled density differences least dense elements (Si, O) at surface of crust silicates layers of the earth: fg 12.14 p. 520 1) crust: solid: thin 2 types a) continental (granite) 70 km thick (less dense) b) oceanic (basaltic) 10 km thick (more dense) 2) mantle (2): p. 519 fg 12.13 2900 km thick,70% of volume a) upper: partly molten rock: 660 km, flows toothpaste b) lower: solid (2225 km) 3) lithosphere: p. 520 fg 12.15 tectonic plates: crust and top of upper mantle part that move across surface of earth 12 plates (continental & oceanic) 4) outer core: p. 519 fg 12.13 2300 km liquid (Fe, Ni) 5) inner core: 1200 km 5000 C solid cores rotate at different speeds earth s protective magnetic fields = magnetosphere C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 5 of 12 Last printed 13/03/2018 1:24 PM
asthenosphere: p. 520 fg 12.14 -below lithosphere -part of upper mantle where convection currents occur p. 520 fg 12.15 source of plate movements spreading ridges (2) p. 522 fg 12.16 ridge push: rising convection currents bring magma to crust surface becoming new crust which pushes the older crust over a) oceanic ridge (ocean) p. 522 fg 12.16 b) rift valley (land)p. 523 fg 12.18 C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 6 of 12 Last printed 13/03/2018 1:24 PM
Process for spreading ridges is subduction: p. 522 fg 12.15 one plate (more dense) will go underneath the other less dense colliding plate subduction zones earthquakes & volcanoes p. 525 fg 12.19A slab pull: p. 522 fg 12.16 gravity pulls old plate near subduction zone downward HW: quiz 12, Cyu 12.1 Plate Interactions: p. 523 fg 12.17 Plate boundaries: 3 1) Divergent: spreading ridges: p. 522 fg 12.16 ocean or rift valley (land) p. 523 fg 12.18 New crust is formed 2) Convergent: 3 types of plate collisions a) oceanic-continental p. 525 fg 12.19A more dense oceanic plates subduct ocean trench (very deep) mountains, volcanoes, earthquakes ex: BC s Coast Mountains Cascade Mountain Range C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 7 of 12 Last printed 13/03/2018 1:24 PM
b) oceanic-oceanic p. 525 fg 12.19B older more dense plate subducts volcanoes island arcs ex: Japan, Indonesia, Aleutians (Alaska) c) continental-continental plate collisions p. 525 fg 12.19C no subduction: equal density massive mountains ex: Himalayas 3) Transform boundaries: p. 526 fg 12.20 plates slide past each other most along spreading ridges faults (breaks in rock layers) earthquakes ex: San Andreas Fault off California Hotspots: place on ocean floor where magma rises and penetrates the the surface of the passing plates Islands are formed ex: fg 12.12 p. 513 C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 8 of 12 Last printed 13/03/2018 1:24 PM
Earthquakes: major 200-800 y http://www.youtube.com/watch?v=ossqavjz4gc Friction between tectonic plates (95%) 80% = ring of fire (Pacific Ocean) p. 528 fg 12.22 Can not predict: Timing, size, location C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 9 of 12 Last printed 13/03/2018 1:24 PM
focus: origin of earthquake: underground epicentre: location on surface above the focus classification of earthquake based upon the depth from focus p. 528 table 12.22 shallow: < 70 km from surface intermediate 70-300 km deep > 300 km 90 % occur < 100 km focus shallow = more damage Seismic waves: earthquake vibrations (waves) are used to determine earth s layers locations C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 10 of 12 Last printed 13/03/2018 1:24 PM
3 types of waves: table 12.3 p. 529 a) body waves (2 kinds): fastest travel inside the earth i) primary waves (P-waves): 6 km/s, fastest move through all states of matter (solid, liquid, gas) like a spring (compression : stretching) ii) secondary waves (S-waves): shear waves: 3.5 km/s, second fastest move through solids only but not liquids or gasses travel like a snake: perpendicular to the direction of travel larger, cause more damage b) surface waves (L waves): travel along surface only slowest ( 1km/s), ripples on a pond Body waves travel at different speeds and directions within the earth due to density differences of the layers Fg 12.23 p. 530 C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 11 of 12 Last printed 13/03/2018 1:24 PM
Seismometers: fg 12.24 p. 530 measure degree of ground movement seismogram (paper with squiggly lines) shows: time, length, and magnitude magnitude = strength Richter scale: each number is 10 times more powerful then the number before 2 = 10x more than 1can feel 3 = 100 x more 4 = 1000 x 5 = 10 000 x 6 = 100 000 x = building damage Time-distance Graph for Seismic Waves: fg 12.25 p. 521 Tells: how fast different waves are traveling You need 3 seismometers to determine the location of an earthquake C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 12 of 12 Last printed 13/03/2018 1:24 PM