Plate Tectonics

Question 1

Describe the crust:

Answer 1

The thin layer of the outer shell that we live on, 5-10km thick beneath oceans and 70km thick beneath continents, lithosphere

Question 2

Describe oceanic plates:

Answer 2

An occasionally broken up layer of basaltic rocks known as sima - silicon and magnesium

Question 3

Describe continental plates:

Answer 3

Bodies of mainly granite rocks, known as sial - silicon and aluminium

Question 4

What is the lithosphere?

Answer 4

The crust and upper mantle, where tectonic plates are formed

Question 5

How thick is the mantle?

Answer 5

2900km

Question 6

What is the asthenosphere?

Answer 6

A layer of soft, plastic like rock that carries the lithosphere

Question 7

How hot is the core?

Answer 7

5000 degrees Celsius

Question 8

What are intrusive rocks?

Answer 8

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 9

What are extrusive rocks?

Answer 9

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 10

What is gravitational sliding?

Answer 10

The movement of tectonic plates under the influence of gravity

Question 11

What is ridge push?

Answer 11

Gravity acting on the weight of the lithosphere near the ridge pushes the older part of the plate in front

Question 12

What is slab pull?

Answer 12

The lithosphere sinks into the mantle under its own weight following subduction, helping to ‘pull’ the rest of the plate with it.

Question 13

What events and landforms occur at Constructive boundaries? (3)

Answer 13

Volcanoes
Mid ocean ridges
Rift Valleys

Question 14

What events and landforms occur at Destructive boundaries? (4)

Answer 14

Powerful earthquakes
Volcanoes
Fold Mountains
Ocean trenches

Question 15

What events and landforms occur at Collision boundaries? (2)

Answer 15

Powerful earthquakes
Fold Mountains

Question 16

What events and landforms occur at Conservative boundaries?

Answer 16

Powerful earthquakes

Question 17

What is jigsaw fit evidence for tectonic theory?

Answer 17

Similarity in outlines of West Africa and South America as well as other continental areas. best fit at 1000m below sea level

Question 18

What is geological fit evidence for tectonic theory?

Answer 18

Ancient rock outcrops from South America and West Africa from over 2000 million years ago were continuous

Question 19

What is Tectonic fit evidence for tectonic theory?

Answer 19

Fragments of the Caldeonian mountain belt are found in Scotland, England, Greenland, Canada and Scandinavia

Question 20

What is glacial deposit evidence for tectonic theory?

Answer 20

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

Question 21

What is fossil evidence for tectonic theory?

Answer 21

Bands of identical fossils lie across continents, particularly of organisms which could not have travelled

Question 22

What happens at a conservative boundary?

Answer 22

2 plates do not directly collide but slide past one another

Question 23

What happens at a constructive boundary?

Answer 23

2 plates are moving apart, leaving a gap for magma to rise up through. Volcanoes form but don’t erupt with force and earthquakes occur

Question 24

What are rift valleys common?

Answer 24

Where 3 plates meet at a junction

Question 25

What happens at destructive boundaries?

Answer 25

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

Question 26

What happens at collision boundaries?

Answer 26

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

Question 27

Where do rift valleys form?

Answer 27

On constructive boundaries

Question 28

How do rift valleys form?

Answer 28

• 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 29

What is the Benioff zone?

Answer 29

The further the rock descends, the hotter it gets. Together with the heat from friction begins to melt the plate to magma

Question 30

What boundaries do ocean trenches form at?

Answer 30

Destructive

Question 31

What is a convection current?

Answer 31

Convection currents, that occur within the molten rock in the mantle, act like a conveyor belt for the plates. Tectonic plates move in different directions. The direction of movement and type of plate margin is determined by which way the convection currents are flowing.

Question 32

What is seafloor spreading?

Answer 32

a geologic process in which tectonic plates—large slabs of Earth’s lithosphere—split apart from each other. Seafloor spreading and other tectonic activity processes are the result of mantle convection.

Question 33

How do fold mountains form?

Answer 33

where two or more of Earth’s tectonic plates are pushed together. At these colliding, compressing boundaries, rocks and debris are warped and folded into rocky outcrops, hills, mountains, and entire mountain ranges. Fold mountains are created through a process called orogeny.

Question 34

How do ocean ridges form?

Answer 34

Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth’s tectonic plates spread apart. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.

Question 35

How do ocean trenches form?

Answer 35

feature of convergent plate boundaries, where two or more tectonic plates meet.
dense lithosphere melts or slides beneath less-dense lithosphere in a process called subduction, creating a trench.

Question 36

How do island arcs form?

Answer 36

Where two oceanic plates converge the denser crust subducts the other. This creates a trench. As the oceanic plate descends it melts, and the magma rises forming a volcanic island chain, known as an island arc.