-Similar geology: mountain: ranges, folds, rock age, -Similar fossils: fg 12.4 p km apart across salt water ocean? Mesosaurus (fresh water)

Transcription

1 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 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 km apart across salt water ocean? Mesosaurus (fresh water) Cynognathus & Lystsrosaurus (land animals) Glossopteris (mild climate plant fern) Page 1 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

2 Climate: fg 12.5 p. 509 patterns of paleoglaciation in Antarctica: formed by decomposition of living things ( 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 b) fg 12.7 p. 510 underwater mountain ranges: Mid-Atlantic Ridge (MAR) Page 2 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

3 c) age of ocean: fg 12.8 p. 511 changes from new on either side of Mid-Atlantic Ridge (MAR) to old, farther away from the Mid-Atlantic Ridge vid3 d) thickness of sediment: fg 12.8 p. 511 thin near Mid Atlantic Ridge (MAR), thick away from MAR 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 y: (S pole N pole) ***** geographic poles: axis of rotation of the earth, do not change much**** Page 3 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

4 ii) paleomagnetism: fg 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 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 Page 4 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

5 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 Features of Plate Tectonics p billion years ago (bya): liquid earth cooled density differences least dense elements (Si, O) at surface of crust silicates layers of the earth: fg p ) 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 km thick,70% of volume a) upper: partly molten rock: 660 km, flows toothpaste b) lower: solid (2225 km) 3) lithosphere: p. 520 fg 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 km liquid (Fe, Ni) 5) inner core: 1200 km 5000 C solid cores rotate at different speeds earth s protective magnetic fields = magnetosphere Page 5 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

6 asthenosphere: p. 520 fg below lithosphere -part of upper mantle where convection currents occur p. 520 fg source of plate movements spreading ridges (2) p. 522 fg ridge p ush: rising convection currents bring magma to crust surface becoming new crust which pushes the older crust over a) oceanic ridge (ocean) p. 522 fg b) rift valley (land)p. 523 fg Page 6 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

7 Process for spreading ridges is subduction: p. 522 fg 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 gravity pulls old plate near subduction zone downward Plate Interactions: p. 523 fg Plate boundaries: 3 1) Divergent: spreading ridges: p. 522 fg ocean or rift valley (land) p. 523 fg 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 Page 7 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

8 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 plates slide past each other most along spreading ridges faults (breaks in rock layers) earthquakes ex: San Andreas Fault off California Page 8 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

9 Hotspots: place on ocean floor where magma rises and penetrates the the surface of the passing plates Islands are formed ex: fg p. 513 Earthquakes: major y Friction between tectonic plates (95%) 80% = ring of fire (Pacific Ocean) p. 528 fg Can not predict: Timing, size, location Page 9 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

10 focus: origin of earthquake: underground epicentre: location on surface above the focus classification of earthquake based upon the depth from focus p. 528 table surface shallow: < 70 km from intermediate 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 Page 10 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

11 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, ripples on a pond Page 11 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

12 Body waves travel at different speeds and directions within the earth due to density differences of the layers Fg p. 530 Seismometers: fg p. 530 measure degree of ground movement seismogram (paper with squiggly lines) shows: time, length, and magnitude Page 12 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx

13 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 = x 6 = x = building damage Time-distance Graph for Seismic Waves: fg p. 521 Tells: how fast different waves are traveling You need 3 seismometers to determine the location of an earthquake Page 13 of 13 D:\New school folder sept\bc Science 10 New\Unit 4\CH 12\Notes\Ch 12 - Red Notes.docx