ch 2.1 -- plate tectonics

Question 1

plate tectonic theory

Answer 1

• 3-layered structure
• constantly moving tectonic plates

Question 2

internal structure

Answer 2

1) core
- thickest (3300km)
- highest temp (4400-6000C)

2) lithosphere
- uppermost mantle + crust
- divided into tectonic plates

3) asthenosphere
- semi-solid (heat from core causes rocks to melt & from magmaaa)

Question 3

convection currents
[desc]

Answer 3

• heat movement within mantle
• driving force of overlying plates
• within hot, softened mantle

Question 4

convection currents
[process]

Answer 4

1. core heat – mantle material GAINS HEAT –> less dense –> rises
2. rising material SPREADS under RIGID crust –> exerts driving force on 2 sides, DRAGS AWAY from eo
   ** DIVERGENT boundary formed
3. mantle material LOSES HEAT –> less dense –> sinks
4. plates PULLED tgt, convection currents collide
   ** CONVERGENT formed
5. sinking material heats up near core, cycle repeats

Question 5

slab pull force
(gravity controlled subduction of DENSER plate)

Answer 5

1. plates differ in density
2. DENSER oceanic plate PULLED DOWN by gravity
3. SUBDUCTS beneath less dense - oceanic SINKS beneath continental
4. sinks DEEPER under own weight
   –> pulls rest of plate, more convergence on one side

Question 6

seafloor spreading

Answer 6

• mid oceanic ridges
• magma rises through, COOLS & SOLIDIFIES –> new oceanic crust

*200 mil years –atlantic ocean has grown, africa & south america pushed apart

Question 7

evidence of sea floor spreading supporting plate tectonic theory
[age]

Answer 7

1) NEARER to crest of mid-oceanic ridge
- younger
- progressively older
2) crest — spreading centre
- magma cools & solidifies
- continuous formation — > older sea floor pushed further
3) new crust SPREADS laterally on both sides

**NOT random or isolated