🌋3.1.5.2 - Plate Tectonics

Question 1

How thick is the mantle?

Answer 1

2900km

Question 2

What are intrusive rocks?

Answer 2

Rocks formed by the cooling of molten Magma, that crystallises and solidifies slowly below the surface. Forms coarse grained igneous rocks. Vertical dykes and inclined sills may form within.

Question 3

What are extrusive rocks?

Answer 3

Lava that is in contact with the air or sea. It cools, crystallises and solidifies much quicker than Magma that is still underground. Fine grained rocks with small crystals.

Question 4

What events and landforms occur at Destructive boundaries?

Answer 4

Powerful earthquakes
Volcanoes
Fold Mountains
Ocean trenches

Question 5

What is glacial deposit evidence for tectonic theory?

Answer 5

300 million year old deposits found in Africa, Australia, Antarctica, South America and India suggest ancient ice sheet

Question 6

Where are rift valleys common?

Answer 6

Where 3 plates meet at a junction

Question 7

What happens at destructive boundaries?

Answer 7

Dense oceanic plate descends beneath less dense continental plate. Oceanic plate melted due to friction forming magma

Question 8

What happens at collision boundaries?

Answer 8

Two plates of similar densities move together, causing the material between them to buckle and rise up

Question 9

Where do rift valleys form?

Answer 9

On constructive boundaries

Question 10

How do rift valleys form?

Answer 10

Magma rises and plates move apart
Over a magma chamber, crack and faults appear
Blocks of crust descend into mantle, creating steep sided valleys
Central plateaus sink in the middle, forming lakes

Question 11

What boundaries do ocean trenches form at?

Answer 11

Destructive

Question 12

Crust

Answer 12

Earth’s outer shell, between 6-70km thick

Question 13

Mantle

Answer 13

Molten/ semi-molten layer rock layer

Question 14

Outer Core

Answer 14

Molten outer layer of the core, mainly iron

Question 15

Inner Core

Answer 15

Solid centre, made of iron and nickel alloys - up to 5000°c

Question 16

Asthenosphere

Answer 16

Layer beneath the lithosphere that’s semi-molten and the plates float on

Question 17

Lithosphere

Answer 17

Crust and the rigid upper section of the mantle, divided into the tectonic plates

Question 18

Oceanic Crust- Thickness

Answer 18

6-10km

Question 19

Oceanic Crust- Age

Answer 19

> 200million

Question 20

Which is denser- oceanic or continental crust?

Answer 20

Oceanic

Question 21

Oceanic Crust- Example of rock

Answer 21

Basalt

Question 22

Continental Crust- Thickness

Answer 22

30-70km

Question 23

Continental Crust- Age

Answer 23

<1500million

Question 24

Continental Crust- Example of rock

Answer 24

Granite

Question 25

What are the 2 internal energy sources?

Answer 25

Primordial Heat Radiogenic Heat

Question 26

What’s primordial heat?

Answer 26

Heat left over from Earth’s formation

Question 27

What’s radiogenic heat?

Answer 27

Heat produced by the decay of isotopes like Uranium 238 By far the greatest source, but slowly diminishing

Question 28

Explain Alfred Wagner’s theory (1912)

Answer 28

Continental Drift- 300 million years ago Pangea existed

Question 29

List 5 pieces of evidences supporting continental drift

Answer 29

Fossil Fit Tectonic Fit Geological Fit Jigsaw Fit Paleomagnetism

Question 30

Fossil Fit Example

Answer 30

Mesosaurus found in South Africa and East America

Question 31

What type of fossils are looked at? Why?

Answer 31

Land mammals Don’t swim, don’t lay eggs

Question 32

Tectonic Fit Example

Answer 32

Caledonian mountain belt found in Scotland, Canada and Greenland- form a continuous linear pattern when reassembled

Question 33

Why does tectonic fit support Continental Drift?

Answer 33

As mountain belts have to be made under the same conditions in the same location

Question 34

Geological Fit Example

Answer 34

Mapping South America and West Africa reveals continuous rock outcrops over 2,000 million years old

Question 35

Jigsaw Fit Example

Answer 35

Coastlines of South America and West Africa match to a depth of 1,000m below current sea level

Question 36

How can gaps and overlaps in jigsaw fit be explained?

Answer 36

Coastal erosion Coastal deposition Rises in sea level Changes in land level

Question 37

How does paleomagnetism explain Continental Drift?

Answer 37

. Roughly every 400 million years the Earth’s magnetism changes . At mid ocean ridges, there are striped symmetrical patterns where the rock has moved apart due to sea floor spreading . Shows that the plates are moving

Question 38

Sea Floor Spreading

Answer 38

Movement of oceanic crust away from constructive plate margins at mid-ocean ridges

Question 39

Slab Pull

Answer 39

After subduction, the cooler, heavier edge of the lithosphere sinks into the mantle under its own weight, pulling the plate with in

Question 40

Ridge Push

Answer 40

The higher elevation at mid ocean ridges causes gravity to push the lithosphere that’s further from the ridge

Question 41

Gravitational Sliding

Answer 41

Movement of tectonic plates as a result of gravity

Question 42

Benioff Zone

Answer 42

Where plates melt in the mantle due to increasing heat and friction

Question 43

Constructive Margin

Answer 43

Plates move apart Magma rises from the asthenosphere and cools, filling the gap

Question 44

Constructive Margin Features (and examples)

Answer 44

Shield volcanoes- Eyjafjallajokull Earthquakes Rift valleys- East African Rift Valley Mid-Ocean Ridges- Mid-Atlantic Ridge

Question 45

Oceanic- Oceanic Margin

Answer 45

2 Oceanic plates move towards eachother Faster/ denser subducts Melts in Benioff Zone Less dense molten material rises

Question 46

Oceanic- Oceanic Margin Features (and examples)

Answer 46

Ocean trenches- Mariana Trench Island Arcs- West Indes Earthquakes Composite volcanoes- Montserrat Tsunamis- Boxing Day

Question 47

Oceanic- Continental Margin

Answer 47

Oceanic and continental move towards eachother Denser oceanic subducts Melts in Benioff Zone Less dense molten material rises

Question 48

Oceanic- Continental Margin Features (and examples)

Answer 48

Ocean Trenches- Peru-Chile Trench Composite volcanoes- Cotopaxi Fold mountains- Himalayas

Question 49

Continental- Continental Margins

Answer 49

Continental plates move towards eachother Both plates have a lower density than asthenosphere Can’t subduct Collide and rise upwards

Question 50

Continental- Continental Margin Features (and examples)

Answer 50

Earthquakes Fold Mountains- Himalayas

Question 51

Conservative Margin

Answer 51

Plates move past eachother Friction between plates= stress builds Suddenly released

Question 52

Conservative Margin Features (and examples)

Answer 52

Fault line- San Andreas Shallow earthquakes

Question 53

Hotspots

Answer 53

Small area with unusually high concentration of radioactive elements below the surface (Magma Plumes)

Question 54

Hotspot Feature (and example)

Answer 54

Shield volcanoes- Mauna Loa, Hawaii

Question 55

Magma Plume

Answer 55

Rising column of hot rock at a plate margin or through a plate