Tectonic Processed And Hazards

Question 1

Describe the distribution of earthquakes

Answer 1

• Found in clusters along plate boundaries

* 70% roughly found in the ‘Ring of Fire’ in the Pacific Ocean

Question 2

What is the oceanic fracture zone?

Answer 2

A belt of activity through the oceans along the mid-ocean ridges, coming ashore in Africa, the Red Sea, the Dead Sea rift and California

Question 3

Name the three types of plate boundary and what they do

Answer 3

• Divergent- plates moving away from eachother
• Convergent- one plate submerging under another
• Conservative- plates moving along side eachother

Question 4

What is formed at destructive (convergent) plate boundaries?

Answer 4

• Surface volcanoes- most active and explosive types

* Large mountain ranges

Question 5

What is formed at a divergent plate boundary?

Answer 5

• Rift volcanoes- less explosive and more effusive

Question 6

What is formed at conservative plate boundaries?

Answer 6

• Shallow focus earthquakes

* No volcanic activity

Question 7

What is the lithosphere?

Answer 7

The surface layer of the Earth, the rigid outer shell composed of the crust and upper mantle

Question 8

Where are hotspot volcanoes found?

Answer 8

In the middle of tectonic plates, fed by mantle plumes

Question 9

What is a volcanic hotspot?

Answer 9

An area in the mantle from which heat rises as a hot thermal plume from deep in the Earth.

Question 10

Describe the process of a volcanic hotspot forming

Answer 10

• High best and lower pressure at the base of the lithosphere enable the melting of the rock.
• This molten magma rises through cracks and erupts to form active volcanoes on the earths surface.
• As the tectonic played move over the stationary hotspot, the volcanoes are rafted away and the new ones form in their place.
• As oceanic volcanoes move away from the hotspot, they cool and subside, producing older islands, atolls and seamounts
• Over long periods of time this can also create a chain of volcanoes

Question 11

What are the two types of crust?

Answer 11

• Thin oceanic crust, which underlies the ocean basins, and is composed of mainly basalt
• Thicker continental crust, which underlies the continents, and is composed of mainly granite

Question 12

Describe the role of convection currents in ‘slab pull’

Answer 12

• Heat which comes from the Earths core rises within the mantle to drive convection currents, which in turn move the tectonic plates.
• These convection currents operate as cells

Question 13

What is the end of the ‘slab pull’ called?

Answer 13

The trench (the part where the lithosphere goes into the mantle)

Question 14

What lies beneath the lithosphere?

Answer 14

The asthenosphere

Question 15

What is paleomagnetism?

Answer 15

A technique involving the reconstruction of paleomagnetic reversals, used to date the age of new tectonic crust

Question 16

What is the Benioff Zone?

Answer 16

An area of seismicity corresponding with the slab being thrust downwards in a subduction zone.

Question 17

What is the hypocentre?

Answer 17

The ‘focus’ point within the ground where the strain energy of the earthquake stirred in the rock is first released.

Question 18

What is the focal length?

Answer 18

The distance between the hypocentre and the epicentre and on the surface

Question 19

Describe the 4 steps of an earthquake being generated

Answer 19

1. The movements are preceded by a gradual build up of tectonic strain, which stores elastic energy in crustal rocks
2. When the pressure exceeds the strength of the fault, the rock fractures
3. This produces the sudden release of energy, creating seismic waves away from the point of fracture
4. The brittle crust then rebounds either side of the fracture, which is the ground shaking (the earthquake being felt on the surface)

Question 20

What does a seismometer do?

Answer 20

Measures the amount of ground shaking during an earthquake, recording both the vertical and horizontal movements of the ground.

Question 21

What are the three types of seismic waves?

Answer 21

• Primary (P) waves
• Secondary (S) waves
• Love (L) waves

Question 22

What is a P wave?

Answer 22

• A primary wave
• Vibrations caused by compression
• They spread quickly from the fault at a rate of about 8km/sec

Question 23

What are S waves?

Answer 23

• Secondary waves
• Vibrate at right angles to the direction of travel and cannot travel through liquids
• Move at around 4km/sec

Question 24

What are L waves?

Answer 24

• Love waves
• Surface waves with the vibration occurring in the horizontal plain
• They have a high amplitude

Question 25

Which are the most destructive types of seismic wave and why?

Answer 25

S and L waves because the have a bigger amplitude and energy force

Question 26

Name 2 serious secondary hazards from earthquakes

Answer 26

• Liquefaction

* Landslides

Question 27

What is soil liquefaction?

Answer 27

The process by which water saturated material can temporarily lose normal strength and behave like a liquid under the pressure of strong shaking.

Question 28

What is intensity?

Answer 28

A measure of the ground shaking

Question 29

What is magnitude?

Answer 29

The amount of movement, or displacement, in the fault, which is in turn a measure of energy release

Question 30

Describe the global distribution of tsunamis

Answer 30

Most are generated at subduction zones

Question 31

Name 6 human and physical factors which affect the impact of a tsunami

Answer 31

• The duration
• The wave amplitude
• The physical geography of the coast
• The degree of coastal ecosystem buffers (coral)
• The timing of the event
• The degree of coastal development

Question 32

name 12 volcanic hazards

Answer 32

lava flows, lava domes, pyroclastic fall, lateral blast, volcanic gases, health effects of gases, pyroclastic flows, pyroclastic surge, lahars, avalanche, earthquakes and tsunamis

Question 33

what is a pyroclastic flow?

Answer 33

frothing magma ejecting hot gases and pyroclastic materials, which contains glass shards, pumice, crystals and ash. They can get up to 1000 degrees.

Question 34

what is a tephra?

Answer 34

when a volcano erupts, materials like rock fragments get ejected into the atmosphere. It can vary in size from ‘bombs’ to fine dust.

Question 35

what gases normally come out of a volcano?

Answer 35

water vapour, sulfur dioxide, hydrogen, carbon monoxide and carbon dioxide

Question 36

what is a lahar?

Answer 36

volcanic mudflows generally composed of fine sand and silt material

Question 37

what is a jokulhlaup?

Answer 37

a type of glacial outburst flood, which are very sudden with rapid discharges of water,ice and debris from a glacial source.

Question 38

what does the Degg’s Model show?

Answer 38

the interaction between hazards, disaster and human vulnerability.

Question 39

what is a hazard?

Answer 39

a natural event that has the potential to threaten both life and property

Question 40

what is a disaster?

Answer 40

a natural hazard which causes significant impact on a vulnerable population.

Question 41

what five factors creates the relationship between risk, hazards and people?

Answer 41

1. unpredictability
2. lack of alternatives
3. dynamic hazards
4. cost-benefit
5. ‘Russian roulette reaction’

Question 42

what is the equation for risk?

Answer 42

risk= hazard x exposure x (vulnerability divided by manageability)

Question 43

what two trends does the disaster risk and age index highlight?

Answer 43

ageing populations and the acceleration of risk in a world that is increasingly exposed to a range of hazard types.

Question 44

what factors does the pressure and release model have on it?

Answer 44

root causes->dynamic pressures->unsafe conditions