Tectonic Cycle

Question 1

explain the magnetism of the earth (dynamo theory of electromagnetism)

Answer 1

the molten outer core flows constantly around the inner core

this causes an electrical current which generates the magnetic field

Question 2

why do different parts of plates move at different speeds

Answer 2

due to the curved nature of the plates

Question 3

do plates with more continental or oceanic crust move slower

Answer 3

plates with lots of continental crust move more slowly

Question 4

is continental or oceanic crust older?

Answer 4

continental much older

Question 5

what happens to plates with no subduction zone

give an example

Answer 5

they grow. indian and atlantic ocean are getting bigger

Question 6

what eventually happens to divergent plate margins

Answer 6

they start off on continents but become an ocean. eg. east african rift will become a sea like the red sea

Question 7

give an example of a mature ocean basin

Answer 7

atlantic ocean

Question 8

what two processes can occur at a convergent plate boundary

Answer 8

uplift or subduction

Question 9

what determines which plate will sinks in an oceanic-oceanic plate collision

Answer 9

angle and velocity

Question 10

how does thinning of crust at ocean basins occur

Answer 10

magma rises and heats the crust until only the top is lithosphere

Question 11

how deep is the mariana deep ocean trench

Answer 11

11km

Question 12

what occurs at the benioff zone

Answer 12

earthquakes

Question 13

why can we only find evidence of ancient geological events in the continents?

Answer 13

oceanic crust is always being destroyed

Question 14

what is a craton

Answer 14

stable core of a continent’s lithosphere made of very ancient rock

Question 15

what is an orogen

Answer 15

mountain or orogenic belts where collision occurs

Question 16

how long ago did plate tectonics begin to operate like today

Answer 16

at least 2 bil years ago

Question 17

what was the impact of the last ice age melting on the plates

Answer 17

crust rose and is still rising in some parts. This proves that magma must be viscous and slow-moving

Question 18

what part of the continental plate has attained isostatic stability?

Answer 18

cratons

Question 19

what processes can cause orogens to sink or rise iso-statically?

Answer 19

mountain building or erosion

Question 20

where is gravity strongest and why

Answer 20

at the poles, as the earth is an ellipsoid and flatter at the poles

Question 21

name 4 impacts that plate tectonics have on the earth today

Answer 21

1. modern orogens influence climate zones and plants and animals
2. chemicals exchanged between seawater and rock
3. gas released into the atmosphere,
4. carbon rich matter sequestered in sediments under the sea