Unit 9 Mini Case Studies

Question 1

Global distribution of earthquakes

Answer 1

Significant tectonic activity in the Pacific Ring of Fire encircling the Pacific Ocean
Destructive in the Andes Mountains or Japan trench
Constructive in the Mid-Atlantic ridge
Transform in the San Andreas Fault in California and the Alpine Fault in New Zealand
Intraplate in the New Madrid seismic zone in the USA
Subduction sonce in the Tonga or Mariana trench

Question 2

Global distribution of volcanoes

Answer 2

Especially in the Pacific Ring of Fire with 75% of all active volcanoes
Destructive in the Andes Mountains and the island arcs of Japan and the Philippines
Constructive in the Mid-Atlantic Ridge and Iceland
Hotspots in the Hawaiian Islands and Yellowstone
Shield volcanoes in Iceland and Mauna Loa in Hawaii

Question 3

Global distribution of tsunamis

Answer 3

Mainly in areas like the Pacific Ring of Fire. Coastal regions like Japan, Indonesia and Chile are especially at risk

Question 4

Examples of island arcs

Answer 4

Aleutian Islands off the coast of Alaska USA
Japanese Archipelago
Lesser Antilles in the Caribbean
The Philippines
The Mariana Islands

Question 5

Examples of hotspots

Answer 5

Hawaii Islands with the Pacific plate moving over a hotspot
Yellowstone has a continental hotspot below it
Iceland is a hotspot that contributes to volcanic and geothermal activity
Galapagos islands formed from volcanic activity due to a hotspot

Question 6

Examples of mid ocean ridges

Answer 6

Mid-Atlantic ridge runs down the centre of the Atlantic ocean separating the Eurasian and North American plate on one side and the African and South American on the other. The East Pacific Rise is a section of mid ocean ridge in the Pacific
Indian Ocean Ridge

Question 7

Disposal of liquid waste causing earthquakes

Answer 7

In the Rocky Mountains in Colorado wastewater was injected into underlying rocks during the 1960s. Water was contaminated by chemical agents and transport of toxic waste for offsite disposal was too expensive. It was therefore disposed of down a 3500m deep well. Disposal began in March 1962 and a series of minor earthquakes followed where there was no activity before. Between 1962 and 1965 700 minor earthquakes were recorded. The injection of waste into bedrock lubricates and reactivates faults that were inactive. The more wastewater injected, the larger the number of minor earthquakes. In 1966 the well was filled in and the number of recorded earthquakes fell

Question 8

Underground nuclear testing causing earthquakes

Answer 8

In 1968 testing of 1200 tonne bombs in Nevada set off 30 minor earthquakes in 3 days. Since 1966 the island of Moruroa has been the site of 80 underground nuclear explosion tests. Over 120000 live on the island. In 1966 a 120000 tonne nuclear device was detonated producing radioactive fallout 300km downwind

Question 9

Fracking causing earthquakes

Answer 9

The use of high powered water to break shale rocks triggered 2 earthquakes in Lancashire in 2011. This is a reason why Chinese engineers have not tried to develop the Sichuan province for shale gas which is a tectonically active area after a major earthquake in 2008

Question 10

Increased crustal loading causing earthquakes

Answer 10

In 1935 the Colorado River was dammed by the Hoover Dam to form Lake Mead. As the lake filled over 10 years the underlying rocks adjusted to the increased load of over 40 km^3 of water, long dormant faults were reactivated causing 6000 minor earthquakes. Over 10000 events were recorded up to 1973, 10% of which were strong enough to be felt

Question 11

Major earthquakes and focus depth

Answer 11

Haiti 2010 - 13km deep
Sichuan 2008 - 10km deep
Christchurch 2011 - 5km deep

Question 12

Hindu Kush Afghanistan earthquake 25th March 2002

Answer 12

A series of earthquakes lasting 10 hours killed 900, inured 4000 and left 20000 homeless in a remote mountain region. Towns were flattened. The region is remote and poor and recent droughts left it without the resources to cope with an earthquake. The houses were inappropriate to withstand ground shaking

Question 13

Taiwan earthquake 30th March 2002

Answer 13

Occurred in a tectonically active region known as the Taiwan Collision Zone where the Philippine plate is subducting beneath the Eurasian plate. The focus was 10km below the surface

Question 14

Volcanic gases example

Answer 14

Lake Nyos in Cameroon in 1986 killed 1700 from CO2 poisoning

Question 15

Volcanic tsunamis example

Answer 15

Krakatoa in 1883 tsunami killed 36000

Question 16

Sichuan 2008

Answer 16

In May and earthquake M7.9 occurred on the eastern rim of Tibet overriding the Sichuan basin. The crust rose 9m up a shear face due to compressional forces. Epicentre area was 300x10km and 15000 secondary landslides, rockfalls and debris flows killed 20000. It concentrated energy at the top of slopes maximising landslide impacts. There was flooding as 33 lakes were created by landslide dams causing some flash flooding. There were 10000 potential rockfalls in deforested areas but the lag time makes it hard to link them to the original earthquake preventing reconstruction funds being claimed

Question 17

Nevado del Ruiz impacts

Answer 17

Is a stratovolcano where the Nazca plate is subducting under the South American plate capable of explosive eruptions. In 1985 20% of snow cover was melted by pyroclastic flows and channels 100x4m were eroded into the icecaps. Lahars 50m thick crushed and eroded everything in their path. Later, part of the ice cap melted causing rivers to flow and dams to burst causing mudflows over Armero. A flood then went over Rio Lagunillas from an upstream lake that was displaced by lahars. This caused 23800 deaths in Armers and 2000 elsewhere

Question 18

Nevado del Ruiz government issues

Answer 18

The government was sued for not having warning or preparation systems by 1000 people for $45 million. The government was eventually cleared of responsibility but was a catalyst for improvement in disaster protection in Colombia and systems at provincial levels

Question 19

Boxing Day 2004 tsunami

Answer 19

Followed one of 4 largest earthquakes with the Indian plate subducted under the Burma plate causing a 1600km fault rupture with most slip in the southern 400km. The primary hazard was the tsunami which caused 280000 deaths in 5 hours. Sumatra and Sri Lanka were hit hardest. Banda Aceh had 31000 deaths. Bangladesh was in an area of slow procession so reduce water displacement. In Simeulue people know from the 1907 tsunami to evacuate to inland hills after the initial earthquake so only 7 out of 78000 died

Question 20

Lake Nyos Cameroon impacts

Answer 20

Is 2k wide and 200m deep. In 1986 lots of gas escaped from the lake and travelled to a village up to 25km away. The clouds of gas were 50m thick travelling 70km/h. 1700 were suffocated and 3000 cattle died as well as all animal life but not plants. The gas was CO2 and deprived people of oxygen

Question 21

Lake Nyos Cameroon source and responses

Answer 21

The source was a basaltic chamber of magma which leaked and accumulated in Lake Nyos. The water was warmer near the surface and colder and denser at the bottom which absorbed the CO2. There was a disturbance at the bottom of the lake causing overlying pressure to be reduced allowing the CO2 to escape. Only 66% of the CO2 escaped and it is building up again so there is a potential for disaster but authorities are trying to drain the CO2 with pumps

Question 22

Sichuan 2008 earthquake impacts

Answer 22

850000 deaths
5300 children died in collapsed schools that were not built to building standards
375000 injured
4.8 million homeless
$146 billion to rebuild and develop region
15000 landslides
10000 potential rockfalls
33 lakes with debris over 10m deep

Question 23

Syrian earthquake background

Answer 23

On february 6th 2023 a M7.8 earthquake struck Southern Turkey and north west Syria followed by a M7.5 aftershock
The region has consistently experienced tectonic activity but this one was the most severe since the Aleppo earthquake of 1822

Question 24

Causes of the Syrian earthquake

Answer 24

Turkey is located along 2 major fault lines along with the movement of 3 major plates where the African, Arabia and Eurasian plates converge. This results in westward compression of the Anatolian block along the East and North Anatolian faults. The east Anatolian fault (EAF) is a 700 km long transform fault with slip rates decreasing east to west. The Dead Sea fault (DSF) is a transform fault between the Arabian and African plates with faster movement in the south compared to the north . The EAF consists of vertical or nearly vertical fractures which involve horizontal movement of cracks. In 2023 multiple segments of the fault failed simultaneously causing a large earthquake. The 2023 earthquake originated from the DSF due to movement between the Arabia and African plates causing the rupture of the southern EAF and the northern DSF. from the Hatay Junction it extent to the northeast and southwest. Tremors were detected in Cyprus, Lebanon, Iraq and Jordan
The initial earthquake caused a 300 km surface rupture and along with the transform movement there was vertical displacement reaching 11.4 m. the second earthquake causing another 125 km of rupture. Overall the causes were the result of highly complex plate movements that proved exceptionally challenging to predict

Question 25

Geological effects of the Syrian earthquake

Answer 25

Liquefaction occurred in former lake beds, river valleys and coastal areas at the southern end of the EAF
This led to ground failure and lateral spreading
Coastal areas and ports experienced widespread damage due to liquefaction
Large residential areas, Hatay airport and canacls were affected, causing flooding
In Iskenderun a sea-water incursion 200 m island was caused by rupture subsidence and a minor tsunami

Question 26

Impacts of the Syrian earthquake

Answer 26

Affected 18 million people in Turkey and SYria causing 55,000 deaths and 130,000 injuries
2.6 million were accommodated in tent cities and 1.6 million on the streets
300,000 buildings were destroyed or rendered unusable
It accounted for 9% of Turkey’s GDP in 2023
Disruption to roads leading to rural areas devastated livelihoods from agricultural production resulted in short term food shortages and long term disruption to farming incomes
Water pipes and sewers were disrupted increasing the risk of diseases especially with the living conditions and shelters. 1 in 7 health facilities were partially functions
Thousands were traumatized and long term investment in mental health services will be needed
5.4 million children are at risk of anxiety, depression and PTSD on top of the impacts of COVID-19

Question 27

Factors affecting the scale of disaster of the Syrian earthquake

Answer 27

Winter weather
Time of day
Large child population
Syrian civil war since 2011
Transboundary issues
International response

Question 28

Challenges to recovery for Syria

Answer 28

Long term displacement
Reconstruction of homes and infrastructure
Over 90% of Syrian refugees depend on humanitarian assistance for survival
Economic decline and global inflation. Syria has seen a price increased of over 800% in the last 2 years resulting in 12.1 million people facing food insecurity
The economic downturn has increased the risk of child labour, gender violence, early marriage and other exploitation
COVID-19 was a threat due to overcrowded conditions making it hard to improvement public safety measures
The war in Ukraine impact food supplies

Question 29

Future threat to Syria

Answer 29

Turkey has 579 dams which leads to Syria and Iraq being highly vulnerable in the event of a dam burst but they lack the financial and political leverage to hold Turkey accountable
Turkey is constructing a nuclear power station in an earthquake prone area where a potential meltdown could endanger the whole southeast Mediterranean
Istanbul’s large population and geographical location means no level of preparedness can fully mitigate the impacts of a large earthquake

Question 30

LEDC building design

Answer 30

Pakistan straw houses
Haiti has concrete roofs and not properly reinforced walls
Peru houses are reinforced with plastic mesh
Indonesia brick walls are framed and connected to the roof

Question 31

San Francisco land use planning

Answer 31

Roads and houses YES on:
- flat to gentle slopes subject to local shallow sliding, soil creep and settlement
- gentle to moderately steep slopes in solder stablised landslide debris, subject to settlement, soil creep and shallow and deep landsliding
- steep to very steep slopes, subject to mass wasting by soil creep, slumping and rock fall
NO on:
- gentle to very steep slopes in unstable material subject to sliding, slumping and soil creep
- moving shallow landslide
- moving, deep landslide subject to rapid failure