Tectonics

Question 1

Seismic hazards

Answer 1

Generated when rocks within 700km of the Earth’s surface come under such stress that they break and become displaced

Question 2

Volcanic hazards

Answer 2

Associated with eruption events

Question 3

Intra-plate earthquakes

Answer 3

These occur in the middle or interior of tectonic plates and are much rarer than boundary earthquakes

Question 4

Volcano

Answer 4

A landform that develops around a weakness in the Earth’s crust from which molten magma, volcanic rock and gases are ejected or extruded

Question 5

Plate tectonics

Answer 5

A theory developed more than 60 years ago to explain the large-scale movements of the lithosphere (the outermost layer of the Earth)
Based around evidence from seafloor spreading and ocean topography, marine magnetic anomalies, palaeomagnetism and geomagnetic field reversals
Knowledge of the Earth’s interior and outer structure is essential for the understanding of plate tectonics

Question 6

Lithosphere

Answer 6

The surface layer of the Earth is a rigid outer shell comprised of the crust and upper mantle
It is on average 100km deep
It is always moving but very slowly, fuelled by rising heat from the mantle which makes convection currents
The distinction between the lithosphere and the atmosphere is one of physical strength rather than a difference in physical composition
The lithosphere is broken down into huge sections which are the tectonic plates

Question 7

Palaeomagnetism

Answer 7

The zone of magma ‘locking in’ or ‘striking’ the Earth’s magnetic polarity when it cools
A tool used to determine historic periods of large-scale tectonic activity through the reconstruction of relative plate motions
They create a geo-timeline

Question 8

Hypocentre

Answer 8

The focus point in the ground where the strain energy of the earthquake stored in the rock is first released
The distance between this and the epicentre on the surface is called the focal length

Question 9

Soil liquefaction

Answer 9

Water saturated material temporarily loses normal strength and behaves like liquid under the pressure of strong shaking
Occurs in saturated soils
Earthquakes can cause the water pressure to increase to the point where the soil particles can move easily, especially in poorly compacted soil

Question 10

Intensity

Answer 10

A measure of ground shaking

It is the ground shaking which causes houses to collapse and the loss of life from hazards

Question 11

Epicentre

Answer 11

The location on the Earth’s crust that is directly above the earthquake focus i.e. the point where an earthquake originates

Question 12

Magnitude

Answer 12

The magnitude of an earthquake is related to the amount of movement, or displacement, in the fault, which is, in turn, a measure of energy release
2004 Indonesia earthquake was magnitude 9.1 as there was a large vertical displacement (15m) along a very long fault distance approx. 1500km
Earthquake magnitude measured at the epicentre, the point on the crust directly above the hypocentre

Question 13

Oceanic plates thickness off…

Answer 13

7-10km

Question 14

Continental plates thickness off…..

Answer 14

25-75km

Question 15

Tsunami

Answer 15

Tsu: port/harbour
Nami: wave/sea
Initiated by undersea earthquakes, landslides or slumps and sometimes volcanic eruptions
Have long wavelengths, 150-1000km
Low amplitudes (wave height) 0.5-5m
Fast velocities, up to 600kph in deep water

Question 16

Hazard

Answer 16

‘A perceived natural/geophysical event that has the potential to threaten both life and property’
It would not be such without people living at or near its location
That is to say, earthquakes would be hazards if there were not people living in the buildings which collapsed
Hazards can occur at the interaction between human and natural factors

Question 17

Disaster

Answer 17

The realisation of a hazard
‘when it causes significant damage to the population’
The Centre for Research on the Epidemiology of Disasters state a hazard is a disaster when:
10 or more people have been killed
100 or more people have been affected

Question 18

Risk

Answer 18

The exposure of people to a hazardous event

The probability of a hazard occurring that leads to the loss of lives/livelihood

Question 19

Resilience

Answer 19

The ability of a system, community or society exposed to hazards to resist, absorb and recover from the effects of a hazard

Question 20

Development

Answer 20

Linked to an improving society
The provision of local services, acquisition of economic assets, improved productivity and reducing vulnerability to natural disasters
Low levels of development are closely associated with high levels of risk and vulnerability to natural disasters

Question 21

Inequality

Answer 21

Refers to an unfair situation or distribution of assets and resources
May also be used when people, nations and non-state players have different levels of authority, competence and outcomes

Question 22

Governance

Answer 22

How individuals and institutions, public and private, manage their common affairs
A continuing process where conflicting views and diverse interests may be accommodated and co-operative action may be taken
Formal institutions and regimes empowered to enforce compliance as well as informal arrangements that people and institutions have either agreed to or perceive to be in their interest

Question 23

Disaster hotspot

Answer 23

A country or area that is extremely disaster prone for a number of reasons

Question 24

Tectonic hazard profiles

Answer 24

Used to understand the physical characteristics of hazards e.g. volcanic eruption, tsunami, earthquake
Can be used to contrast the same hazard which occurs in contrasting places or at different times
Criteria such as frequency, duration and speed of onset

Question 25

Subduction Zones

Answer 25

The area in the mantle where a tectonic plate melts
Contact between plates sometimes called a megathrust fault
Plates locked together and build friction
Stress released through the megathrust earthquake and seismic waves occur
Enormous stress can be built up before release

Question 26

The process of stress, strain and failure on a tectonic plate

Answer 26

Often called the elastic rebound theory

Question 27

Locked fault

Answer 27

A fault which is not slipping due to frictional resistance being greater than the shear stress across the fault which is stuck
Stress may be held for years and then released as a large magnitude earthquake or when frictional resistance is overcome
2004 Indian Ocean tsunami was a megathrust locked fault which generated huge seismic waves and a tsunami

Question 28

P waves

Primary

Answer 28

The fastest seismic waves
Waves travel through both solids and liquids
Shunting motion
8km/sec

Question 29

S waves

Secondary

Answer 29

Seismic waves which only travel through solids and more with a sideways motion
right angle vibrations
4km/sec

Question 30

L waves

Love

Answer 30

The slowest seismic waves
All energy focussed on the Earth’s crust
surface vibrations in the crust
High amplitude