Plate tectonics (KQ1)

Question 1

What is the internal structure of the earth made up of?

Answer 1

• crust
• lithosphere
• mantle
• aesthenosphere
• core

Question 2

What is the outermost layer of the earth made up of?

Answer 2

• basalt
• granite

Question 3

How thick is the outermost layer of the earth?

Answer 3

• varies from a few km to more than 70km thick

Question 4

What is the lithosphere made of?

Answer 4

• crust

- uppermost mantle

Question 5

What is the mantle made up of (other than lithosphere)?

Answer 5

• aesthenosphere

- mostly solid rock that flows under high temperatures and pressure

Question 6

How thick is the mantle?

Answer 6

• about 2500km thick

Question 7

What is the temperature of the mantle?

Answer 7

• between 800 to 3000 degrees celsius

Question 8

What is the core made up of?

Answer 8

• iron
• nickel
• separated into liquid outer core and solid inner core

Question 9

How thick is the core?

Answer 9

• about 3300km thick

Question 10

What is the temperature of the core?

Answer 10

• between 3000 to 5000 degrees celsius

Question 11

What are the two different types of crust?

Answer 11

• oceanic
• continental

Question 12

Where is the oceanic crust located?

Answer 12

• beneath deep oceans

Question 13

Where is the continental crust located?

Answer 13

• beneath the earth’s land masses
• under shallow seas close to continents

Question 14

What are some characteristics of the oceanic crust?

Answer 14

• denser (basalt)

- thinner (between 5-8km)

Question 15

What are some characteristics of continental crust?

Answer 15

• less dense (granite)
• thicker (35-70km)

Question 16

Why do tectonic plates move?

Answer 16

• plate movement is caused by a combination of convection currents and slab-pull force
• movement of convection currents refer to the movement of heat within the mantle

Question 17

How do convection currents cause plate movement?

Answer 17

• as the mantle is heated by the core, the material expands, rises and spreads out beneath the plates
• this pulls the plates apart as they are dragged along
• as mantle material spreads further, it cools and sinks, pulling the plates along
• the sinking mantle material heats up again as it nears the core, repeating the entire process

Question 18

How does slab-pull force cause plate movement?

Answer 18

• as denser oceanic plates sink at the subduction zone, it pulls the rest of the plate
• this process is known as slab-pull force (pulling force exerted by a dense oceanic plate plunging into the mantle due to its own weight)

Question 19

What happens when oceanic-oceanic plates diverge?

Answer 19

• magma rises from the mantle to fill the gap between the plates as they diverge
• a new seafloor is formed when lava flows out onto the seafloor and then cools and solidifies (seafloor spreading
• it then forms a mid-oceanic ridge

Question 20

What are some characteristics of divergent oceanic-oceanic plate type?

Answer 20

• newly formed (youngest) rocks are closest to the middle of the ridge
• at various points along the ridge, magma builds up above the ocean to form volcanic islands

Question 21

What are some examples of landforms caused by 2 oceanic plates diverging around the world?

Answer 21

• iceland

- mid-atlantic ridge found in the middle of the atlantic ocean

Question 22

What happens when continental-continental plates diverge?

Answer 22

• when plates diverge, they are stretched
• this causes fractures at the plate boundary
• the land in between the 2 continental plates then sinks to form a linear depression (rift valley)
• this divergence can cause continents to break apart

Question 23

What are some examples of landforms around the world caused by continental plates diverging?

Answer 23

• East African Rift Valley

Question 24

What happens when 2 oceanic plates converge?

Answer 24

• denser plate subducts beneath the less dense plate
• a deep oceanic trench is formed at the point of subduction
• subducted oceanic plates causes the mantle material above it to melt, forming magma
• magma rises through the cracks to form a volcano and eventually, a chain of islands
• earthquakes may occur due to friction

Question 25

What are some examples of landforms around the world caused by 2 oceanic plates converging?

Answer 25

• marina trench
• marina islands (eventually)

Question 26

What happens when continental-continental plates converge?

Answer 26

• little to no subduction occurs due to both plates being too thick & buoyant
• layers of rock on the upper part of the crust are compressed together
• this causes them to fold upwards or sideways, forming fold mountains

Question 27

What are some examples of landforms that form when 2 continental plates converge?

Answer 27

• Himalayas

Question 28

What happens when oceanic-continental plates converge?

Answer 28

• denser oceanic plate subducts
• oceanic trench forms at the subduction zone while fold mountains form on the continental plate
• volcanoes are also formed on the continental plate when magma rises through the cracks to the surface
• earthquakes may occur

Question 29

What are some examples of landforms caused by oceanic and continental plates converging around the world?

Answer 29

• The Andes, Chile

Question 30

What are transform plate boundaries?

Answer 30

• where plates slide past each other, resulting in a transform fault
• tremendous stress builds up and is eventually released as an earthquake

Question 31

What are some examples around the world of landforms caused by transform plate boundaries?

Answer 31

• San Andreas fault between the pacific and north American plates