Deck 1 - Tectonics distribution, plate boundaries and mechanisms of plate movement

Question 1

What are two categories of tectonic hazard?

Answer 1

1) Seismic

2) Volcanic

Question 2

Where do the majority of earthquakes occur?

Answer 2

The majority of earthquakes are found along plate boundaries. About 70% of all earthquakes are found in the ‘Ring of Fire’ in the Pacific Ocean

Question 3

What is a intra-plate earthquake?

Answer 3

Intra-plate earthquakes occur in the middle of a tectonic plate

Question 4

What secondary hazards are associated with earthquakes?

Answer 4

Landslides, avalanches, tsunamis

Question 5

Where are the majority of volcanoes found?

Answer 5

There are about 500 active volcanoes around the world with on average 50 erupting each year. The majority are found on plate boundaries with a large concentration around the Pacific Ocean (Ring of Fire

Question 6

What is a hot spot volcano?

Answer 6

An intra-plate volcano that is located above a mantle plume

Question 7

What is a constructive (divergent) plate margin?

Answer 7

A plate boundary where tectonic plates are moving away from each other allowing for magma to move to the surface to create new land

Question 8

What is a destructive (convergent) plate margin?

Answer 8

A plate margin where tectonic plates are moving towards each other. Oceanic plate is denser than continental plate meaning it is subducted

Question 9

What is a conservative plate margin?

Answer 9

A plate margin where tectonic plates move alongside each other. Plates are either moving in opposite direction or the same direction at different speeds

Question 10

What is a collision boundary?

Answer 10

A destructive margin where both plates are of equal density meaning that neither plate subducts resulting in an upwards buckling creating fold mountains such as the Himalayas.

Question 11

Which type of plate boundaries do you find earthquakes at?

Answer 11

All

Question 12

Which type of plate boundary do you find volcanoes at?

Answer 12

Constructive and destructive

Question 13

What are the two models for the internal structure of the Earth?

Answer 13

Physical properties and chemical composition

Question 13

Where is the lithosphere found and what is it made of?

Answer 13

The lithosphere is the outermost layer of the Earth when viewed from the physical properties model. It is about 100km thick and is thicker beneath continents. Continental lithosphere is made of ‘granitic’ rocks whereas oceanic lithosphere is made of ‘basaltic’ rocks.

Question 14

Where is the asthenosphere found and what is it made of?

Answer 14

The asthenosphere is 250km thick and is found to a depth of 350km. It is below the lithosphere and is made of solid rock that is ductile so flows easily.

Question 15

Where is the mesosphere found and what is it made of?

Answer 15

The mesosphere is around 2500km thick and is found between the asthenosphere and outer core. It is made of solid rock and is less ductile than the asthenosphere but is still capable of flowing.

Question 16

What is the difference between the outer and inner core?

Answer 16

The outer core is made of liquid iron and nickel whereas the inner core is made of solid iron and nickel.

Question 17

Where is the crust found and what is it made of?

Answer 17

The crust is the outermost layer of the Earth in the chemical structure model. Continental crust is 10-70km thick and is made of silica ricks rocks. Oceanic crust is 2-10km thick and is made of basaltic rocks making it denser than the continental crust.

Question 18

Where is the mantle found and what is it made of?

Answer 18

The mantle is below the crust and is around 3488km thick. It is made of peridotite that is solid and ductile.

Question 19

Where is the core found and what is it made of?

Answer 19

The core is found in the centre of the Earth and is 2883km thick and is made of iron and nickel.

Question 20

Who first proposed in 1912 that all the continents had been connected as one giant supercontinent they named Pangea?

Answer 20

Alfred Wegener

Question 21

How does the convection current model propose that tectonic plates move?

Answer 21

The core heats the base of the mantle. As heat rises it creates a current that moves upwards towards the crust. Once at the crust the current moves sideways (both ways) and drags the plate above with it. The current eventually cools and sinks back down to the base of the mantle. As it sinks it drags the overriding plate into the mantle. The current heats back up an a convection cell is created.

Question 22

How does the slab pull/ridge push model propose that tectonic plates move?

Answer 22

This model suggests that the density of the tectonic plates is important. The denser oceanic crust subducts beneath the light continental plate which drags the remaining plate with it, creating its own momentum. At the other end of the plate magma is able to rise to the surface to fill the gap that has been created and pushes the tectonic plates away in either direction. This is ridge push.

Question 23

Which model of tectonic plate movement do scientists currently believe is the most likely and why?

Answer 23

Slab pull/ridge push because tectonic plates have been measured to be moving fasted at a subduction zone suggesting this is the driving force in plate movement.

Question 24

What is paleomagnetism and what did it prove?

Answer 24

Paleomagnetism refers to the rock record of changes in the Earth’s magnetic field. As igneous rocks cool the minerals align themselves ‘north’. Through time magnetic north has not stayed stationary but has wandered. At mid ocean ridges scientists have mapped alternating strips of igneous rocks with minerals aligned north and south at eqi-distance from the volcanoes. They used this to prove sea flooring spreading as it proves that new land is created at the same speed either side of the volcanic ridge.