Tectonic processes and hazards

Question 1

Stages of the hazard management cycle:

Answer 1

Mitigation (prevention), before
Preparedness (adaptation), before
Response, during disaster
Recovery, after disaster

Question 2

Difference between hazard mitigation and adaptation:

Answer 2

Mitigation - strategies meant to avoid, delay or prevent hazard events
Adaptation - strategies used to reduce the impacts of hazard events

Question 3

Movement of plates is driven by 4 processes:

Answer 3

.Mantle convection
.Slab pull
.Sub-duction
.Seafloor spreading

Question 4

Seafloor spreading meaning?

Answer 4

Occurs in mid-ocean ridges. Hot magma rises up, hardens and forms oceanic crust.
This new crust pushes tectonic plates apart in process called seafloor spreading .

Question 5

What is a mid ocean ridge?

Answer 5

Long underwater mountain range formed by lava eruptions through Earth’s crust

Question 6

What is palaeomagnetism?

Answer 6

Every 400,000 years the magnetic fields in rocks change direction.
Palaeomagnetism confirms that seafloor is spreading

Question 7

Difference between oceanic and continental crust

Answer 7

.Oceanic is denser and thinner
.Continental is thicker,less dense and older than oceanic crust

Question 8

Where are tectonic plates formed and floating?

Answer 8

.Between crust and upper mantle, the solid lithosphere where tectonic plates are formed.

.In the semi-molten asthenosphere is where tectonic plates float.

Question 9

How are intra plate earthquakes formed?

Answer 9

Plates move over a spherical surface, zones of weakness are created.
Intra plate earthquakes happen at these zones of weakness.

Question 10

What are mantle plumes?

Answer 10

They exist below the tectonic plates and are stationary.
As tectonic plates move slowly over it, this produces chain of volcanic islands.

Question 11

What is volcanic hotspot?

Answer 11

Hotspot is an area on Earth that exists over an isolated mantle plume in the upper mantle.

Magma plume causes melting and thinning of rocky crust and widespread volcanic activity creating an island arc (Hawaii is an example).

Question 12

Divergent margin meaning and an example:

Answer 12

Plates moving away from each other
-On land Rift valleys are formed
-Ocean ridges which eventually form islands if underwater.
An example is Heimaey, volcanic island near Iceland. Rift valley is east African rift

Question 13

What type of lava is produced at divergent plate margin and its features?

Answer 13

Very hot lava with low silica content so low viscosity (basaltic)

Question 14

Convergent margin meaning and examples:

Answer 14

Plates moving towards each other

-Oceanic-continental: Composite volcano and deep sea trench formed (Nazca plate subducting south America plate forming Andes mountain range with many volcanoes, and Peru trench).

-Oceanic-oceanic: Deep sea trench formed (e.g. Mariana trench)

-Continental-continental: Fold mountains formed (Himalayas which grow 10 mm every year)

Question 15

What type of lava is produced at convergent plate margin and features?

Answer 15

Cooler lava with higher silica content so more viscous. (Andesitic)
Lava is viscous so could block vents causing pressure to build and a violent eruption occurs.

Question 16

Example of shield and composite volcano:

Answer 16

Shield volcano: Mauna Kea on Hawaii
Composite volcano: Mount St Helens in US

Question 17

What is the benioff zone?

Answer 17

Area where deep earthquakes caused by friction of plate subduction occurs

Question 18

Why are there no volcanoes in Himalayas?

Answer 18

Rock is too thick, Continental plate meets another continental plate

Question 19

Rank earthquake waves from fastest to slowest:

Answer 19

1)Primary
2)Secondary
3)Love

Question 20

Where does each earthquake wave focus its energy?

Answer 20

Primary: Travels through solids and liquids inside the earth
Secondary: Travels only through solids inside the earth
Love: All of its energy focused on Earth’s surface

Question 21

What are aftershocks and why are they cause?

Answer 21

These are smaller earthquakes which occur for a period of time after an earthquake, occur as result of readjusting along part of the fault that slipped at time of main earthquake

Question 22

Case study for aftershock:

Answer 22

In 2011 an aftershock struck Christchurch, New Zealand caused more damage and loss of life than main earthquake in 2010, in 2010 it was centered in rural area whereas in 2011 it was closer to the city

Question 23

Definition of natural hazard, disaster and mega-disaster:

Answer 23

1)Natural hazard are events that have potential to harm people and property.

2)Disaster is when it has done the harm, Conditions include:

-10 or more deaths
-100 or more people affected
-USS 1 million in economic losses

3)Mega-disaster is where scale of impact may lead to requirement of international aid, occur rarely and affect large populations

Question 24

Predicting volcanic eruptions:

Answer 24

Unlike earthquakes, scientists can often predict volcanic eruptions. Signs include:

-Small earthquakes, magma rising which break rocks, detected by seismograms
-Changes to the slope angle of volcano as magma moves inside, detected by tiltmeter

Question 25

Different players that help manage loss in natural disaster:

Answer 25

1)Aid donors
2)NGOs, important when government struggles to respond
3)Insurance companies
4)Communities

Question 26

Case study for NGOs and for communities:

Answer 26

NGOs:

Pakistan 2005 earthquake where 73 000 died and 3.5 million left homeless, provided immediate needs like safe water for over 700 000 people,6 million blankets and
500 000 tents

Communities:

After earthquake in Afghanistan 2015 villagers in mountain communities set up small groups to help with search and rescue in remote areas, as well as helping with rebuilding in the long-term

Question 27

Reasons why number of earthquakes have risen since 1960:

Answer 27

.Improvements in technology used to monitor earthquakes (seismographs)
.Increase in population so more people occupy hazardous space

Question 28

Trends for natural disasters in the world:

Answer 28

.Reduced number of deaths from better early warning systems, improved building codes and disaster preparedness
.Increased financial cost as infrastructure becomes more developed

Question 29

Aspects shown by a hazard profile:

Answer 29

-Speed of onset
-Magnitude
-Predictability
-Frequency (frequent to rare)
-Areal extent
-Duration

Question 30

Define hydrometeorological hazards:

Answer 30

Natural hazards caused by climate processes (droughts, floods, hurricanes and storms)

Question 31

Case study of hydrometeorological hazard:

Answer 31

Australia drought from 2001 to 2009

Question 32

Case study of hydrometeorological hazard combining with tectonic hazard:

Answer 32

In 1991 the eruption of Mount Pinatubo in Philippines was struck by a typhoon, heavy rainfall which led to increased formation of volcanic ash and destructive lahars.
-Killed 700 people and left 200 000 homeless