Plate margins

Question 1

Divergent plate margin is between…

Answer 1

oceanic crusts.

Question 2

Divergent plate margin- the convection currents…

Answer 2

diverge the plates apart.

Question 3

Divergent plate margin has basaltic…

Answer 3

magma. It contains less silica than granitic magma, less air is trapped, therefore denser.

Question 4

A ridge is formed at…

Answer 4

divergent plate margin and filled with lava.

Question 5

Pahoehoe is…

Answer 5

a form of a basaltic lava flow, with a smooth or rippled surface.

Question 6

Pahoehoe type of lava is common in…

Answer 6

Hawaiian volcanoes.

Question 7

A transform fault margin is…

Answer 7

conservative plate margin.

Question 8

At transform fault margin the plates have…

Answer 8

similar densities.

Question 9

A transform fault margin causes…

Answer 9

strike-slip(almost vertical fractures) and earthquakes.

Question 10

At transform fault margin a lot of energy is…

Answer 10

stored by the tension.

Question 11

At transform fault margin the earthquakes are…

Answer 11

shallow, so more seismic waves reach the surface and they have more energy. This results in stronger earthquakes.

Question 12

At Collision plate margin the plates have…

Answer 12

similar densities.

Question 13

Plates At Collision plate margin are mostly…

Answer 13

continental.

Question 14

Because the atmosphere is less dense than mantel At Collision plate margin…

Answer 14

the crust moves upwards(isostatic uplift) and mountains are formed.

Question 15

At Collision plate margin, sometimes, the asthenosphere…

Answer 15

moves with crust upwards, cools, solidifies and produces layers=folds.

Question 16

Strata is…

Answer 16

a horizontal layer of material made of several parallel layers on each other.

Question 17

Strata is formed by…

Answer 17

the folds At Collision plate margin.

Question 18

At convergent plate margin the oceanic plate…

Answer 18

melts as it is subducted.

Question 19

At convergent plate margin, the plates have…

Answer 19

different densities. Heavier is subducted.

Question 20

At convergent plate margin oceanic trench is…

Answer 20

formed.

Question 21

Benioff zone is…

Answer 21

the area where the oceanic plate is scratched against the continental plate. This is the focus of an earthquake.

Question 22

The subduction zone is where…

Answer 22

the oceanic plate is subducted under the continental crust.

Question 23

At convergent plate margin isostatic change causes…

Answer 23

eustatic change, which is a change in the ocean basin. Tsunamis are triggered.

Question 24

The magma chamber is located…

Answer 24

under the earth surface.

Question 25

The magma chamber is...

Answer 25

a large pool of molten rock. There is a very high temperature and pressure=melting the rock above and causing fractures in the rock.

Question 26

Volcanic island areas have a margin between...

Answer 26

two oceanic crusts.

Question 27

At Volcanic island areas both plates are...

Answer 27

weak and have similar densities.

Question 28

At Volcanic island areas, an accretionary wedge is...

Answer 28

formed.

Question 29

At Volcanic island areas, there is subduction of...

Answer 29

the plate below the accretionary wedge.

Question 30

Volcanic island areas the trapped...

Answer 30

magma pops up as the pressure builds up by the subduction of one plate.

Question 31

Tephra is...

Answer 31

rock and other particles ejected by volcanoes. It must be larger than 2mm, otherwise, it is ash.

Question 32

Types of volcanoes:

Answer 32

- dome volcanoes | - strato / composite volcanoes

Question 33

Dome volcanoes are created by...

Answer 33

small masses of rhyolitic magma, which are very viscous as they are high in silica.

Question 34

The dome grows by...

Answer 34

an expansion of the lava within, and the mountain forms from material spilling off the sides of the growing dome.

Question 35

A lot of gas is...

Answer 35

trapped in the rhyolitic magma, so the lava dome can violently explode, releasing a huge amount of material(ash, tephra)

Question 36

Types of magma:

Answer 36

- basaltic | - rhyolitic

Question 37

A pyroclastic flow is...

Answer 37

a fast-moving current of hot gas and tephra.

Question 38

Rhyolitic magma is high in...

Answer 38

silica, so very viscous and contains high levels of gas. The temperature is around 650-800 degrees.

Question 39

Basaltic magma has quite low...

Answer 39

silica content, so it has low viscosity and traps much less gas. Temperature is around 1000-1200 degrees.

Question 40

An example of a composite volcano is...

Answer 40

Mount St. Helens.

Question 41

A composite volcano has...

Answer 41

conduit system that channels magma from deep within the Earth to the surface. They can have clusters of vents, with lava breaking through walls on the sides of the mountain.

Question 42

A composite volcano can grow...

Answer 42

a thousand meter tall.

Question 43

Composite volcanoes erupt with...

Answer 43

great violence.

Question 44

In a composite volcanoes pressure builds as...

Answer 44

gases, under immense heat and pressure, are dissolved in the liquid rock. When the magma reaches the conduits the pressure is released and the gases explode.

Question 45

Dome volcanoes can be found...

Answer 45

in the crater of Mount St Helen.

Question 46

Cinder cones are created by single...

Answer 46

vent.

Question 47

Cinder cone volcano is built as...

Answer 47

gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall around the vent to form an oval cone.

Question 48

Basaltic magma is present in...

Answer 48

cinder cone volcanoes.

Question 49

At the subduction zone, deep sea...

Answer 49

ocean trenches are found.

Question 50

Ocean trenches are...

Answer 50

long, narrow depressions in the ocean floor, with depths up to 11 km.

Question 51

Tranches are found adjacent...

Answer 51

to land areas associated with islands arcs.

Question 52

The trench is usually...

Answer 52

asymmetric, with the steep side towards the land mass.