Tectonic

Question 1

What are the structures of a volcano?

Answer 1

Crater- bowl shaped opening at summit

Caldera- large depression formed when a volcano erupts and collapses (eg sun moon lake)

Vent- passageway for magma

Magma chamber- reservoir of magma stored here

Secondary cone- secondary exit for lava to flow out

Question 2

What is difference between oceanic and continental plates?

Answer 2

Oceanic crust
Lies beneath the ocean
Very thin (5-8km)
Denser (eg basalt)

Continental crust
Lies beneath land mass and shallow seas
Thicker (30-60km)
Less dense (eg granite)

Question 3

Characteristics of Shield Volcano?( Both shield and strato volcanoes mostly located near plate boundaries eg Pacific Ring of Fire)

Answer 3

1) Broad summit
2) Gentle slope formed with low viscosity lava(low silica content) which flows easily and quickly over a large area and solidifying
3) Wide base
4) Shorter height, lower altitude
5) Less explosive eruptions as low silica lava does not trap as much gas

Question 4

Characteristics of stratovolcano?

Answer 4

1) Narrow summit
2) Steep slopes near summit, gentler near base
3) Formed with high viscosity lava(high silica content) which flows with more resistance over a smaller area
4) Concave shape
5) Greater height and altitude
6) More explosive eruptions due to larger gas pressure built up at vent, solidified high silica lava may block vent
7) May have secondary cone as high silica lava needs an alternative route to erupt from

Question 5

How is a shield volcano formed?

Answer 5

1) Formed when plates diverge
2) Magma rising from vent is of low viscosity, (flows easily and quickly over a large area before cooling)
3) Forms gentle slopes as each layer is broader
4) With successful eruptions, base widens as lava accumulates

Question 6

How is a stratovolcano formed?

Answer 6

1) Formed when plates converge
2) Magma rising from vent is of high viscosity, (flows with high resistance over a smaller area before cooling and solidifying)
3) Forms steeper slopes near summit and gentler slopes at base
4) With successful eruptions, builds high volcano with concave shape
5) Has secondary cones as high silica lava needs alternative route to erupt from

Question 7

What are Earthquakes?

Answer 7

● Earthquakes are - vibration of the earth’s crust
● Caused by sudden release of stored energy in rocks found along fault lines
● Plate movements produce frictional energy which is stored
● Build up of stress in rocks
● Earthquake releases energy in form of seismic waves
● Waves radiate from focus, of which the point directly above that on the earth’s surface
is the epicenter
● Aftershocks occur due to stress in ground after earthquake event

Question 8

What are the 7 factors affecting the intensity of an earthquake? (MISTPLD)

Answer 8

1. Magnitude (Richter Scale)
2. Infrastructure and Services
3. Soil Type
4. Time of occurrence
5. Population Density
6. Level of Preparedness
7. Distance from Epicenter

Question 9

How does Magnitude affect earthquake intensity?

Answer 9

● Stronger shockwaves, higher intensity tremors result in (more) collapse
of infrastructure (NOTE: Comparative words used if needed)
● Places nearer to plate boundary (Eg JPN) face greater casualties and
destruction of infrastructure due to stronger shock waves

Question 10

How does Infrastructure and Services affect earthquake intensity?

Answer 10

● Roads blocked - traffic congestion, access for emergency vehicles limited
● Communication lines cut, water pipe burst - no clean water - dysentery, cholera

Question 11

How does Soil Type affect earthquake intensity?

Answer 11

● Loose and unconsolidated soil amplify seismic waves, resulting in more damage to infrastructure
● Affected by liquefaction, soil sinks into the ground, swallowing cars and houses, and people lose their homes or may be injured or killed.

Question 12

How does Time of Occurrence affect earthquake intensity?

Answer 12

● Higher chance of survival in the day as most people are at work or in school, and out and about, so it is water to evacuate to safer ground, less casualties and death
● Lower chance of survival at night as most people are at home sleeping, unaware of earthquakes and when buildings and when buildings collapse, more casualties and death (eg. Sun Moon Lake region Taiwan 1999, 2400 people died as eq occurred couple h after midnight)

Question 13

How does Population Density affect earthquake density?

Answer 13

● More people affected when an earthquake strikes, more casualties, death and severe destruction
● More larger cities, more buildings are skyscrapers collapsing and killing people.

Question 14

How does Level of Preparedness affect earthquake intensity?

Answer 14

● Infrastructure and buildings not well reinforced, more risk of collapsing
during earthquake, resulting in more casualties and severe injury.
● Precautionary measures not in place (warning systems or evacuation plans), more casualties as people are untrained and there is insufficient time to seek shelter without a warning system

Question 15

How does Distance from Epicenter affect earthquake density?

Answer 15

● Stronger shockwaves, more intense tremors, increased risk of collapse of buildings, causing more casualties (distance from plate boundary)

• eg. Christchurch New Zealand 2011, epicentre a few km away from city centre, city suffered more damages than areas further away from city

Question 16

What are the 5 impacts of earthquakes? (PLLDT)

Answer 16

1. Property and Infrastructure damage
   2.Landslides
   3.Loss of Lives
   4,Disruption of services
   5.Tsunamis

Question 17

Impacts of Property and Infrastructure damage? (EQ)

Answer 17

● Houses and buildings that are not well reinforced may collapse due to earthquakes
● Cause cracks in roads and bridges - disrupting traffic, causing traffic congestion as it is unsafe

Question 18

Impacts of Landslides? (EQ)

Answer 18

● Shockwaves weaken slopes on mountains, loose and unconsolidated soil, along with large rocks fall down rapidly from mountains and damage properties, or injuring and killing people
● Mudslides occur during heavy rain

Question 19

Impacts of Loss of Lives? (EQ)

Answer 19

● People die due to injury and starvation when they are trapped in rubble of collapsed buildings
● Earthquakes cause fire outbreaks

Question 20

Impacts of Disruption of Services? (EQ)

Answer 20

● Roads blocked - collapse infrastructure - traffic congestion and restrict access of emergency vehicles
● Phone and internet lines cut, severing communication services
● Water pipes burst due to vibrations in ground, no clean water supply causes outbreak of water-borne diseases (Eg dysentery, cholera)

Question 21

Impacts of Tsunamis? (EQ)

Answer 21

● Large sea waves form due to oceanic plate movement, and travel inland, for long distances, destroying houses or sweeping away people, causing homelessness and death

Question 22

How are Tsunamis formed?

Answer 22

1. Formed when seismic energy from an offshore earthquake displaces a mass of seawater
2. A large volume of water is lifted and forms a wave of great wave length and low weight height.
3. The wave travels towards the land.
4. On reaching shallower waters, greater friction slows the waves and water behind catches up.
5. This forces waves to increase in wave height and devastate shorelines when it hits.

Question 23

What are the preparedness measures (WILE) , short term (ES) and long term responses (RH) to earthquakes?

Answer 23

Preparedness measures:
Warning and Monitoring Systems
Infrastructure Development
Land Use Regulation
Emergency Drills

Short term responses:
Emergency food and medical supplies
Search and Rescue

Long term responses:
Rebuilding Infrastructure
Healthcare Provision

Question 24

Description and effectiveness of Warning and Monitoring systems and example?

Answer 24

Description:
● Help monitor earthquakes by studying the history of past events and estimates frequency and magnitude of earthquakes to predict them
● Helps detect earthquakes by installing sensors (E) / pressure sensor (T) on seafloor to detect plate movements and vibrations (Describe)

Effectiveness:
● Detecting them earlier gives more time to evacuate civilians to safe ground and shelter

Ineffectiveness:
● Can only give general indication but not precise
information like location, time or magnitude of
future earthquakes
● Prone to false alarms when waves are high (T)
● Earthquakes occur seconds after warning system is sounded, insufficient time for evacuation - more death and casualties (E&T)

Example:
● In Japan, earthquake motion data is gathered
from hundreds of observation stations installed
in bridges and roads, which enable prediction of
earthquakes by monitoring ground motion
● More evacuation time, less death and casualties
● Deep ocean tsunami detectors around Hawaii,
USA to monitor and forecast path of tsunamis

Question 25

Description and effectiveness of Infrastructure Development and example?

Answer 25

Description: ● Houses, and infrastructure like roads are built to withstand vibration of earthquakes, so they do not collapse ● Homes, offices, factories fitted with trip switches so all electrical points are switched off during earthquake Effectiveness: ● Since less buildings and infrastructure collapse in an earthquake, there would be less lives lost and casualties, and reduces damage costs. Ineffectiveness: ● Costly and untested until earthquakes occur ● cost ineffective to retrofit existing buildings Example: ● Taipei 101, a building in Taipei, Taiwan is made of steel and reinforced concrete, which can withstand earthquake vibrations far better than non-reinforced materials. ● This reduces risk of building from collapsing, less death and casualties

Question 26

Description and effectiveness of Land Use Regulation

Answer 26

Description: ● The government implement rules to restrict development in certain areas prone to disaster ● Prohibit constructing new buildings on low lying land prone to tsunamis Effectiveness: ● Prevent buildings and infrastructure from being destroyed, and reducing lives lost in areas vulnerable to earthquakes or tsunamis Ineffectiveness: ● These rules may be implemented in already developed areas, privately-owned ● Costly to compensate those who are evicted ● Private owners reluctant to move as they think hazards will not occur Example: ● In California, USA - all new building developments must not be built across fault lines or area with high liquefaction risk, where ground vibrations cause unstable ground, making it unsafe

Question 27

Description and effectiveness of Emergency Drills

Answer 27

Description: ● Simulates earthquake event, people practice steps to take during an earthquake ● They move to safe locations, listen to instructions by trained personnel, learn first aid, join local response teams to assist rescue works ● educate public on what to do during an earthquake Effectiveness: ● Creates awareness, reduces panic, know what to do ● Reduce time taken to evacuate, less casualties Ineffectiveness: ● Based on scale on past events, emergency scenario unrealistic ● Insufficient time for evacuation as earthquakes are difficult to predict ● More deaths and casualties Example (Effective): ● Disaster Prevention Day, JPN - annual emergency drills simulates earthquake event where all are involved in evacuation to safer places, listening to instructions by trained personnel and learning first aid, join local response teams to aid in rescue Example (Ineffective): ● Earthquake in Tohoku, JPN was on a scale unlike any other they had experienced before, as tsunami breached sea walls, destroy Fukushima power plant ● Hundreds of deaths caused by radiation leakage and collapse of homes ● emergency drills and evacuation was inadequate to prevent loss of lives since the extreme events were uncalled for ● Thus, there was large lost of lives (28k estimate)

Question 28

Description and effectiveness of Emergency food and medical supplies (short term)

Answer 28

Description: Injured were treated and survivors were provided food, clean drinking water to prevent dehydration and spread of diseases Effectiveness: ● Provision of immediate aid help survivors continue with their lives normally Ineffectiveness: ● Medical supplies, food and water may be insufficient, cause social unrest Example: ● After earthquake in Afyon, Turkey in ‘02, Turkish Red Crescent Society delivered thousands of tents, blankets and heaters to the region for use. ● After the earthquake in Port-au-Prince, Haiti in ‘10, people looted and fought for food and medical supplies.

Question 29

Description and effectiveness of Search and Rescue (short term)

Answer 29

Description: ● People trapped under rubble of collapsed buildings are quickly located and freed by sniffer dogs or workers, sometimes using devices or machinery Effectiveness: ● Survivors are found alive successfully after being trapped for weeks without food or water Ineffectiveness: ● Limited time of 3 days to rescue survivors, otherwise they will die eventually because of injury or lack of water or food Example: ● In Tohoku, JPN, after the earthquake in ‘11, sniffer dogs and heat sensors were deployed and successfully rescued many people trapped in rubble. ● Rescue workers only had 3 days to rapidly search 2 towns in Tohoku after the quake in ‘11.

Question 30

Description and effectiveness of Rebuilding Infrastructure (long term)

Answer 30

Description: ● Infrastructure and amenities are rebuilt and improved upon a disaster Effectiveness: ● Authorities develop stricter building codes to ensure infrastructure is restored at a higher safety level than previously Ineffectiveness: ● Reinforced buildings are not protected against tsunamis like they are from earthquakes Example: ● After earthquake in Kobe, JPN, government sent billions of dollars in building earthquake-resistant buildings and technology ● Although many of Chile’s buildings are reinforced against earthquakes, they suffered great damage from an after-resulting tsunami when an earthquake hit in ‘10.

Question 31

Description and effectiveness of Healthcare Provision (long term)

Answer 31

Benefits: - Long-term counselling providing provided to help people manage grief of loss of loved ones, homes and jobs after earthquakes - Problems can be identified and addressed early Risk: - Improving health options such as restoring resilience of people after earthquake can be challenging Example: - A year after Christchurch NZ earthquake in 2011, many people were facing depression and anxiety thus greater number of health workers were deployed in the area - Many survivors of Haiti earthquake in 2010 still continue to lack basic necessities like clean drinking water and food

Question 32

Describe convection currents

Answer 32

- Core heats up mantle material - Causes it to expand and rise, rising magma spreads out beneath plates - Causes plates to diverge - Magma then cools and sinks, converging plates as magma spreads inwards - Sinking mantle material rises again when heated when near core, whole process repeats

Question 33

Describe slab pull force

Answer 33

- Occurs when the dense, sinking oceanic plate at subduction zones pulls the rest of the plate behind it. (Main drive of plate movement)

Question 34

Describe divergent oceanic-oceanic plates

Answer 34

- Core heats up magma - 2 oceanic plates diverge, caused by convection currents in mantle, fractures formed at plate boundary - Magma rises out of mantle through vents to fill gaps between plates, cools and solidifies into lava - Magma cools and solidifies, building up above sea level, forming VOLCANIC ISLANDS - Plates continue to diverge overtime, newer seafloor is formed as more magma rises and cools, solidifies into lava. - Older seafloor moves away from spreading zone (SEA FLOOR SPREADING)

Question 35

Describe divergent continental-continental plates

Answer 35

- Core heats up magma in mantle - 2 convectional plates diverge caused by convectional currents in mantle, fractures formed at plate boundary, caused by tensional force as plates are stretched (FAULTING) - Central block of land in between 2 continental plates subside, forming RIFT VALLEY - When central block of land subsides, forming BLOCK MOUNTAINS between a pair of parallel faults RIFT VALLEY - Deep slopes and sides - Rocky, fairly flat surface - Long linear depression in ground - Presence of trees on valley floor BLOCK MOUNTAINS - Elevated above rift valley, with steep slopes

Question 36

Describe convergent oceanic-oceanic plates

Answer 36

- Core heats up magma in mantle - 2 oceanic plates converge caused by converge currents in mantle - Denser oceanic plate SUBDUCTS under less dense plate, forming oceanic trench at subduction zone - Mantle above subducted oceanic plate melts into magma - Rises through fractures and forms CHAIN OF VOLCANOES

Question 37

Describe convergent continental-continental plates

Answer 37

- Core heats up magma in mantle - 2 continental plates converge caused by convection currents in mantle - Plates TOO THICK and BUOYANT for subduction to occur - Plates break and slide along fractures in crust - Compressional force creates immense pressure, causing layers of rock to buckle and fold - Forming fold mountains - EARTHQUAKES may be triggered

Question 38

Describe convergent oceanic-continental plates

Answer 38

- Core heats up magma in mantle - Oceanic and continental plates converge caused by convection currents in mantle - Denser oceanic plate subducts under less dense continental plate, forming DEEP OCEANIC TRENCH at subduction zone - Magma rises up through fractures, forming VOLCANOES - Continental plates BUCKLE and FOLD, forming FOLD MOUNTAINS

Question 39

Describe transform plate boundaries

Answer 39

- Plates slide past each other causing friction building tremendous stress and energy stored in crust - When rocks cannot hold energy is released - Shock waves of energy radiate out of crust, causing earthquakes