✅HAZARDS 3.1.5.2 - 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 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 C

Question 8

What is gravitational sliding?

Answer 8

The movement of tectonic plates under the influence of gravity

Question 9

What is ridge push?

Answer 9

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

Question 10

What is slab pull?

Answer 10

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

Question 11

What events and landforms occur at Constructive boundaries?

Answer 11

Volcanoes
Mid ocean ridges
Rift valleys

Question 12

What events and landforms occur at Destructive boundaries?

Answer 12

Powerful earthquakes
Volcanoes
Fold Mountains
Ocean trenches

Question 13

What events and landforms occur at Collision boundaries?

Answer 13

Powerful earthquakes

Fold Mountains

Question 14

What events and landforms occur at Conservative boundaries?

Answer 14

Powerful earthquakes

Question 15

What is jigsaw fit evidence for tectonic theory?

Answer 15

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

Question 16

What is geological fit evidence for tectonic theory?

Answer 16

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

Question 17

What is Tectonic (orogenic) fit evidence for tectonic theory?

Answer 17

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

Question 18

What is glacial deposit evidence for tectonic theory?

Answer 18

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

Question 19

What is fossil evidence for tectonic theory?

Answer 19

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

Question 20

What happens at a conservative boundary?

Answer 20

Two plates do not directly collide but slide past one another

Question 21

What happens at a constructive boundary?

Answer 21

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 22

Where are rift valleys common?

Answer 22

Where 3 plates meet at a junction

Question 23

What happens at destructive boundaries?

Answer 23

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

Question 24

What happens at collision boundaries?

Answer 24

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

Question 25

Where do rift valleys form?

Answer 25

On constructive boundaries

Question 26

How do rift valleys form?

Answer 26

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 Mountains often form on the sides

Question 27

What is a Benioff zone?

Answer 27

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

Question 28

What boundaries do ocean trenches form at?

Answer 28

Destructive

Question 29

What are convention currents in the asthenosphere

Answer 29

Movement of hotter material in the mantle rising (causes magma to rise)

Question 30

What is Plate Tectonic Theory

Answer 30

Idea the Earth's surface is split into plates which glide over the Mantle (asthenosphere)

Question 31

Destructive Plate boundary Example: what is the Ring of Fire

Answer 31

Surrounds Pacific 40,000 km Many intense active volcanoes+ earthquakes Krakatoa 1883 eruption, 2010 Japan EQ

Question 32

Destructive Plate boundary Example: what is the Alpide Belt

Answer 32

Includes the Indian Plate, Eurasian Plate. Orogenic (mountains formed, e.g Himalayas) 15,000 km

Question 33

Constructive Plate Boundary: Mid Atlantic Ridge

Answer 33

The largest mountain chain in the world 16000km, is underwater. South American and African Plates

Question 34

Slab Pull

Answer 34

Question 35

Ridge Push

Answer 35

The upwelling of hot material creates a buoyancy effect which creates an ocean ridge. Here the plate experiences the force of gravity, pushing the plates

Question 36

Rift Valley Example

Answer 36

Question 37

What boundary do island arcs form at

Answer 37

Destructive Oceanic and oceanic plates

Question 38

How do island arcs form

Answer 38

Denser oceanic plate subducts In the benioff zone, magma upwelling occurs Volcanic island form

Question 39

What is an example of an island arc

Answer 39

Pacific plate subducts under the Philippine plate Line of volcanic islands including Guam appear

Question 40

What is a plume

Answer 40

a hot column of magma which rises from deep within in the Earth

Question 41

Why does not all volcanic activity occur at a plate boundary

Answer 41

Due to tectonic plate movement away from a hotspot where a volcanic island can form

Question 42

What is a hotspot

Answer 42

A hot spot is an area on Earth over a mantle plume or an area under the crust where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the crust and volcanic activity due to the localised heating between the crust and mantle

Question 43

How do island chains form

Answer 43

Theory: Active volcanoes form from mantle plume above hotspot Tectonic plate moves taking with it the volcano, hotspot remains stationary Another volcano is formed over the hotspot Process continues until a chain is formed Islands furthest from hotspot are oldest

Question 44

Example of an island chain

Answer 44

Hawaiian islands Youngest island is submarine volcano The Loihi Seamount, which will eventually emerge into a new island in the chain Has active shield volcanoes like Mauna Loa 6000km long shows movement of tectonic plates (the plate moves approx. 10 cm a year)

Question 45

What is a sill

Answer 45

if magma moves along horizontal bedding planes, it cools to form sills Often in composite volcanoes Lava can erupt out of - causing volcano eruptions to be unpredictable - not sure where lava will come from

Question 46

What is a dyke

Answer 46

If the magma is intruded along vertical joints, it forms dykes