Important for test info on tectonics

Question 1

What are the 7 major plates from largest to smallest?

Answer 1

1. Pacific
2. Eurasia
3. North America
4. South America
5. Africa
6. Antarctica
7. Australian

Question 2

How large is the pacific plate?

Answer 2

~14000km

Question 3

What type of crust is the pacific plate made of?

Answer 3

Oceanic

Question 4

What is the difference between plate and lithosphere?

Answer 4

A plate is a piece of lithosphere, which can have either continental or oceanic crust (or both) at its top. Continent is the emerged part of a plate

Question 5

What is the position of the mid-Atlantic ridge between south America and Africa?

Answer 5

Symmetrically in the middle

Question 6

What distance is the Mid-Atlantic ridge from South America and Africa?

Answer 6

Both ~2500km

Question 7

Is the Mid-Atlantic ridge segmented or a straight boundary?

Answer 7

Segmented (by strike slip)

Question 8

How long is the longest and shortest ridge segments of the Mid-Atlantic ridge?

Answer 8

Long =~1000km
Short =~50km

Question 9

What is the maximum lateral offset of the Mid-Atlantic ridge?

Answer 9

870km

Question 10

What is an example of where a spreading ridge occurs above sea level?

Answer 10

Iceland

Question 11

What is the bathymetric profile along the south mid-Atlantic ridge?

Answer 11

Ridge is large elevated areas in centre of the ocean.

Coast to coast, the depth increases up to a maximum of -5500km and decreases again where the ridge starts

Question 12

Where is the highest elevation along the Mid-Atlantic ridge?

Answer 12

In the centre at the divergent margin

Question 13

What is the total height of the Mid-Atlantic ridge?

Answer 13

Around 3000m

Question 14

How wide is the Mid-Atlantic ridge?

Answer 14

~2900km

Question 15

Why is the Mid-Atlantic ridge so wide/ what controls this?

Answer 15

elevated area (ridge) is hotter than other oceanic rocks and therefore more buoyant. Temperature decreases from the ridge towards the ocean-continent boundary and so does the elevation (colder = less buoyant = deeper)

Question 16

What is the age distribution of oceanic crust in the Atlantic ocean like?

Answer 16

Symmetric

Question 17

What was the initial opening age of the mid-Atlantic ridge between NW Africa and the USA?

Answer 17

175-180 Ma

Question 18

What is the spreading rate of the Mid-Atlantic ridge between NW Africa and USA?

Answer 18

3.2cm/year

Question 19

What is the sequence of opening and age of the North, central and south Mid-Atlantic ridge?

Answer 19

North Atlantic = 130 Ma (southern part); Central Atlantic = 180 Ma;
South Atlantic = 130 Ma.

Question 20

How old is the oldest oceanic crust?

Answer 20

~280 Ma

Question 21

What has the spreading rate been like in the Central Atlantic?

Answer 21

Relatively constant

Question 22

What does the difference between the age of oceanic and continental crust?

Answer 22

Oceans are continuously recycled during the various Wilson cycles, while continents are not

Question 23

How many types of convergent plate boundary are there?

Answer 23

Ocean-ocean,
ocean-continent,
continent-continent.

Question 24

What is the main large scale product of intra-continental and ocean-continent subductions?

Answer 24

orogenesys

Question 25

What is the main large scale product of intra-oceanic convergent boundaries?

Answer 25

Island arc

Question 26

Is the convergence of the Juan de Fuca plate perpendicular to the trench direction?

Answer 26

Subduction can be oblique to the trench, as for the Nazca plate.

Question 27

What is the overall shape of the down-going plate?

Answer 27

From the abyssal plain, depths increase towards the trench, reaching a maximum depth at the trench where lithosphere inflects downward into the subduction zone

Question 28

What is the overall depth of the overriding plate compared with the down-going plate?

Answer 28

Always higher

Question 29

Along which type of plate margin do volcanoes occur more often?

Answer 29

Convergent margins

Question 30

Where can a large number of volcanoes that are not associated with a plate boundary?

Answer 30

East African rift valley (a new plate margin is developing there as this is a rift)

Question 31

What is the topographic profile and alignment of volcanoes in the East African rift valley?

Answer 31

Are aligned within the rift valley, which is a topographic depression

Question 32

What is the process responsible for the topographic profile and volcano alignment in the east African rift valley?

Answer 32

Continental rifting

Question 33

What is the distance between some volcanoes and trenchs?

Answer 33

South America: 320 km North America: 290 km Japan: 300 km

Question 34

What type of margin do large volcanoes occur?

Answer 34

Convergent

Question 35

Is there a link between depth of the earthquake and distance from the trench?

Answer 35

Yes - depth increases away from the trench reflecting the shape of the subduction zone.

Question 36

What is the distribution of earthquakes on the plate called?

Answer 36

Benioff zone