Physical Geography - Tectonic Processes & Hazards

Question 1

L4 1.3a What scale do scientist use to measure earthquakes and what does it measure?

Answer 1

Moment Magnitude Scale - measures total energy released at the moment it occurs, uses size of the waves, amount of rock movement, area broken by the earthquake, resistance of the affected rocks

Question 2

L4 1.3a How does the Moment Magnitude Scale work?

Answer 2

Logarithmic scale, goes from 1 (smallest) to generally around 10 (largest)

Question 3

L4 1.3a What does the Mercalli scale do?

Answer 3

Takes observations from people who experienced the earthquake and rates them from I (hardly noticed) to XII (catastrophic)

Question 4

L4 1.3a What kind of earthquakes occur at divergent boundaries?

Answer 4

Shallow focus, low mag. (5-6)

Question 5

L4 1.3a What kind of earthquakes occur at convergent (o/c) boundaries?

Answer 5

range of focal depths, high mag. (8-9)

Question 6

L4 1.3a What kind of earthquakes occur at convergent (o/o) boundaries?

Answer 6

range of focal depths, moderate to high mag. (7-9)

Question 7

L4 1.3a What kind of earthquakes occur at convergent (c/c) boundaries?

Answer 7

shallow to moderate focal depths, moderate mag. (6-8)

Question 8

L4 1.3a What kind of earthquakes occur at conservative boundaries?

Answer 8

shallow focus, moderate mag. (6-8)

Question 9

L4 1.3a What is the Wadati-Benioff zone?

Answer 9

Where most pressure is built up and then released during an earthquake. Understanding its depth can help to understand how destructive an earthquake will be

Question 10

L4 1.3a Describe primary waves

Answer 10

Arrives first, travels through crust, mantle, and core, longitudinal wave

Question 11

L4 1.3a Describe secondary waves

Answer 11

Slower than p-waves, travels through crust and mantle, transverse wave

Question 12

L4 1.3a Describe Rayleigh waves

Answer 12

Surface waves, rolling motion (up/down & side/side), responsible for most shaking

Question 13

L4 1.3a Describe Love waves

Answer 13

Surface waves, fastest surface wave, moves side/side as it travels (zig zag pattern)

Question 14

L5 1.3a Describe what liquefaction is and what damage it causes

Answer 14

Loosely packed, water-logged sediments near the ground’s surface which lose their strength due to strong ground shaking, it can cause flash flooding and the uprooting of infrastructure like pipes and manholes

Question 15

L5 1.3a Explain how earthquakes can lead to mass movement and what damage it causes

Answer 15

Seismic waves shake the ground and cause slopes to destabilise and slip, can bury roads, towns, and infrastructure which makes rescuing those in affected areas difficult

Question 16

L5 1.3a Summarise the Christchurch Earthquake Feb. 2011

Answer 16

6.3 mag. shallow focus earthquake, liquefaction was exaggerated because shockwaves of contrasting resonances occurred in the soft horizontal layers underground, 30m thick soft upper layer smacked into the solid layer beneath sending vibrations back to the surface

Question 17

L5 1.3a What engineering was put in place in Christchurch after the 2011 earthquake to protect against the impacts of future events?

Answer 17

Cone Perimeter Testing (CPT) was carried out to assess the susceptibility of soil to liquefaction in different areas of Christchurch (quick and inexpensive but in some places boreholes were dug to explore deeper), new buildings built with stone columns (10m in ground), geogrid of plastic matting, and compacted gravel above to redistribute the weight of the building

Question 18

L5 1.3c What is a tsunami and how is it caused?

Answer 18

A series of larger-than-normal waves which are usually caused by volcanic eruptions or underwater earthquakes

Question 19

L5 1.3c Summarise the causes and impacts of the 2004 Boxing Day Tsunami

Answer 19

Caused by an earthquake off the coast of Sumatra, Indonesia that was 9.0-9.3 mag., thrust moved ocean floor 15m towards Indonesia

Coastal settlements were devastated (70% of residents killed in some villages, 1500 villages destroyed in Sumatra), much infrastructure was destroyed (Andaman & Nicobar cut off as jetties destroyed), economies devastated (60% of fishing fleet & industrial infrastructure destroyed in Sri Lanka, tourism industry lost £25m in Thailand - 120k jobs lost), ecosystems destroyed, vegetation & topsoil destroyed, freshwater supplies contaminated with seawater, $10bn total cost

Question 20

L6 1.2c, 1.3a,b+c Where are volcanoes usually located? Give an example for each location

Answer 20

Along plate boundaries (e.g. Pacific Ring of Fire), at mid-ocean ridges (e.g. mid-Atlantic ridge), and at hotspots which can be in the centre of plates (e.g. Hawaii)

Question 21

L6 1.2c, 1.3a,b+c How do plate boundaries influence what type of eruption occurs?

Answer 21

At divergent plate boundaries lava is usually basaltic so eruptions are less viscous and effusive (shield volcanoes). At convergent plate boundaries lava is usually andesitic or rhyolitic. This means the gas content is higher so the eruptions are more explosive (composite cone volcanoes)

Question 22

L6 1.2c, 1.3a,b+c Summarise the features of a composite volcano. What is its alternative name? What types of lava does it contain?

Answer 22

Steep sides, high silica content - viscous lava, explosive, layers of solidified lava, found on destructive plate boundaries

Contains andesitic and rhyolitic lava

Also known as a strato volcano

Question 23

L6 1.2c, 1.3a,b+c Summarise the features of a shield volcano. What type of lava does it contain?

Answer 23

Gently sloping sides, low silica content - less viscous lava, effusive, found on constructive plate boundaries and hot spots

Contains basaltic lava

Question 24

L6 1.2c, 1.3a,b+c Describe the features of basaltic lava

Answer 24

• Hottest type (1000-1200°C)
• Low silica (50%)
• Low gas content (0.5-2%)
• Low viscosity
• Effusive
• Darker colour
• Found at shield volcanoes

Question 25

L6 1.2c, 1.3a,b+c Describe the features of andesitic lava

Answer 25

• 800-1000°C
• Intermediate silica (60%)
• Intermediate gas content (3-4%)
• Intermediate viscosity
• Moderately explosive
• Lighter colour
• Found at composite volcanoes
• Formed by the subducted oceanic plate melting

Question 26

L6 1.2c, 1.3a,b+c Describe the features of rhyolitic lava

Answer 26

• Coolest (650-800°C)
• High silica (70%)
• High gas content (4-6%)
• High viscosity
• Very violent, cataclysmic
• Lighter volcano
• Found at composite volcanoes (& supervolcanoes)
• Formed by the subducted plate melting

Question 27

L6 1.2c, 1.3a,b+c How do we measure the strength of volcanic eruptions? What is the scale based on? Describe what happens at levels 0, 2, 4, 6, 7, & 8

Answer 27

Volcanic Explosivity Index (VEI) - Logarithmic scale, it is based on the volume of erupted material, the height of the eruption, and the duration of the eruption

0 - gentle flow
2 - bi-weekly
4 - 1-2 yrs
6 - 50-100 yrs, largest in living memory -> global change in temperature (Pinatubo eruption, 1991 -0.5°C global temps)
7 - 500-1000 yrs (Mt. Tambora eruption, 1815, 0.5°C cooling, 90,000 deaths due to famine)
8 - every 50,000 yrs, super eruption, extinction level event

Question 28

L6 1.2c, 1.3a,b+c What is a phreatomagmatic eruption?

Answer 28

When a volcano erupts through water/ice, this can cause large amounts of ash to be emitted

Question 29

L7 Describe what lava flows are and if they are a primary or secondary hazard of volcanic eruptions

Answer 29

Very hot flows of molten rock, can take years to cool, generally not a threat to humans but destroy everything in its path - primary hazard

Question 30

L7 Describe what pyroclastic flows are and if they are a primary or secondary hazard of volcanic eruptions

Answer 30

Dense hot rock, ash, and gases which move quickly across the Earth’s surface, very dangerous to humans - up to 100km/hr - primary hazard

Question 31

L7 Describe what tephra and ash flows are and if they are a primary or secondary hazard of volcanic eruptions

Answer 31

Volcanic ash and rock that erupt from a volcano, larger pieces near the eruption can cause injuries/deaths, poor visibility & slippery roads, roofs collapse, engines become clogged (E15) - primary hazard

Question 32

L7 Describe what gas eruptions are and if they are a primary or secondary hazard of volcanic eruptions

Answer 32

Magma contains dissolved gases - H2O, CO2, SO2, gases can travel thousands of km - primary hazard

Question 33

L7 Describe what lahars are and if they are a primary or secondary hazard of volcanic eruptions

Answer 33

Mudflows that travel quickly down volcanoes, can’t outrun, when an eruption melts ice/snow or when rain mixes with ash - secondary hazard

Question 34

L7 Describe what jökulhlaup are and if they are a primary or secondary hazard of volcanic eruptions

Answer 34

When heat from a volcanic eruption melts a glacier causing flooding - secondary hazard

Question 35

L8 What is the difference between a natural hazard and a natural disaster?

Answer 35

A natural hazard is an event such as an earthquake, volcano, or tsunami whereas a natural disaster is when a hazard effects a vulnerable population that can’t cope, usually leading to deaths and widespread poverty

Question 36

L8 What is the hazard risk equation?

Answer 36

Risk = (Hazard x Vulnerability)/Capacity

Where risk is the probability of harm/loss taking place, hazard is the type of disaster, time of day, mag., and duration, vulnerability is the ability to anticipate, cope, & recover, and capacity is the ability to protect lives from destruction & restoration of affected areas

Question 37

L8 Summarise the 2010 Haitian Earthquake

Answer 37

12th Jan 2010, magnitude 7.0 earthquake struck 24km from the capital

Question 38

L8 What were the physical factors that played a part in the devastation of Haiti in the 2010 earthquake?

Answer 38

• Shallow focus (13km) - increased ground shaking
• Liquefaction on loose soil - foundations of buildings sank
• Epicentre 24km from Port-au-Prince - 2 million people (Haiti’s most densely populated city)

Question 39

L8 What political, social, and economic factors turned the 2010 Haiti earthquake into a disaster?

Answer 39

• Developing country - poor, resources spent on immediate issues, like disease, rather than earthquake protection
• High corruption - lack of commitment to improvement of infrastructure and living standards
• Lack of building regulations - buildings poorly built, dense urban env. - difficult for rescue teams to work
• Lack of disaster prep. - govt. officials and emergency services simply didn’t know what to do
• Extreme poverty - didn’t have resources to cope with an earthquake

Question 40

L8 What were the impacts of the 2010 earthquake on Haiti?

Answer 40

• Only 1 airport & limited ports/roads - prevented aid from arriving/being distributed fairly, led to more deaths
• A quarter of govt. officials killed - lack of organisation for relief
• Oct. 2010 Cholera outbreak - spread as a lack of medical professionals, by 2015 9000 had died

Question 41

L8 What was Haiti’s recovery effort like after the 2010 earthquake?

Answer 41

• 13bn aid donated - however most remained with non-Haitian organisations & govts.
• Concerns about corruption - organisations unwilling to give aid to the Haitian govt. - did it themselves, this prevented Haiti’s self-sufficiency as money did not go to local businesses/industries
• Slow progress - by 2015 80,000 still lived in temporary housing/tents, cholera still ongoing
• Some improvements however - new infrastructure, health stats increasing, govt. becoming more able to cope - issued a warning about 2013 Hurricane Sandy which saved lives, afterwards took a leading role in organising aid

Question 42

L9 Summarise the 2008 Chinese (Sichuan) Earthquake

Answer 42

12th May 2008, intra-plate earthquake struck Sichuan, mag. 7.9, triggered landslides that led to a quarter of the deaths

Question 43

L9 Why was Sichuan vulnerable in 2008 earthquake?

Answer 43

• Poorly constructed buildings - corrupt govt. officials ignored building codes & accepted bribes to allow builders to take shortcuts
• Damage was concentrated in rural areas and towns

Question 44

L9 What were the social & economic impacts of the 2008 Chinese (Sichuan) earthquake?

Answer 44

• 1000s of schools fell - 5300 children killed
• 5m made homeless
• 45m affected
• However, China was a large country with a growing economy so had the money to pay for rescue and aid teams

Question 45

L9 Describe the responses to the 2008 Chinese (Sichuan) earthquake

Answer 45

China’s strong central govt. was able to respond quickly and effectively:
- 130,000 soldiers & relief workers deployed within hours - some parachuted/hiked into mountains
- Medical services swiftly restored to prevent disease outbreaks
- Govt. pledge of $10bn for rebuilding, wrote off debt for those w/o insurance

Question 46

L9 What was the situation 2 years after the Chinese (Sichuan) earthquake?

Answer 46

• 97% of reconstruction projects were started
• 99% of 196,000 farmhouses were rebuilt
• 216 transport projects were ongoing/completed

Question 47

L9 Summarise the 2011 Japanese (Sendai) earthquake

Answer 47

11th March 2011, mag. 9.0 under Pacific, 100km East of Sendai (island of Honshu), seawater displacement caused a tsunami - 10m high, reached 10km inland

Question 48

L9 Why was Sendai vulnerable in 2011?

Answer 48

• Located on East coast of Japan - frequent hazards
• Nuclear power plant right on the coast - Fukushima, 47,000 evacuated, still a 20km exclusion zone today

Question 49

L9 What was Japan’s preparation like for the 2011 earthquake?

Answer 49

• Good building construction - strict regulations (75% built w/ earthquakes in mind vs. 0% in Haiti), low levels of corruption
• Well developed plans - vulnerable areas had walls, evac. shelters, & evac. routes, earthquake emergency kits in offices & homes, 1 min. early warning system, emergency drills in schools & businesses

Question 50

L9 What was Japan’s response to the 2011 earthquake?

Answer 50

• Within 24hrs 110,000 troops were mobilised
• All radio & TV stations switched to earthquake coverage
• Bank of Japan offered $183bn to Japanese banks to protect the economy
• Quickly accepted rescue & recovery teams from 20 countries (Haiti teams delayed by damage & bad coordination and China was not used to accepting international aid)