C:\New folder jan 2018\BC Science 10 New\Unit 4\CH 12\Notes\ch 12 tectonics.docx Page 1 of 12 Last printed 08/05/2018 7:44 AM

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 2 of 12 Last printed 08/05/2018 7:44 AM

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 3 of 12 Last printed 08/05/2018 7:44 AM

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 4 of 12 Last printed 08/05/2018 7:44 AM

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 5 of 12 Last printed 08/05/2018 7:44 AM

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 6 of 12 Last printed 08/05/2018 7:44 AM

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 7 of 12 Last printed 08/05/2018 7:44 AM

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 8 of 12 Last printed 08/05/2018 7:44 AM

b) oceanic-oceanic p. 525 fg 12.19B

older more dense plate subducts

→ volcanoes → island arcs

ex: Japan, Indonesia, Philippines, 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 9 of 12 Last printed 08/05/2018 7:44 AM

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 10 of 12 Last printed 08/05/2018 7:44 AM

focus: origin of earthquake: underground

epicentre: location on surface above the focus

classification of earthquake based upon the

depth from focus / hypocenter

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 11 of 12 Last printed 08/05/2018 7:44 AM

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 12 of 12 Last printed 08/05/2018 7:44 AM

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