1.3

Question 1

Focus

Answer 1

Origin of the earthquake in the crust.

Question 2

Epicentre

Answer 2

Above the focus on the earth’s surface.

Question 3

Seismograph

Answer 3

What earthquakes are recorded on.

Question 4

Body waves

Answer 4

P waves, S waves

Question 5

Surface waves

Answer 5

Love waves, Rayleigh waves

Question 6

P waves

Answer 6

Fastest to travel, back and forth motion, travels through solids and liquids.

Question 7

S waves

Answer 7

60% slower than P waves, up and down motion, travels through solids only.

Question 8

Love waves

Answer 8

Surface wave, travels through solids only, side to side motion.

Question 9

Rayleigh waves

Answer 9

Surface waves, travels through solids only, elliptical motion, responsible for most of the shaking felt by people. Spreads furthest from the epicentre.

Question 10

Primary effects of seismic waves

Answer 10

ground shaking, crustal fracturing

Question 11

Secondary effects of seismic waves

Answer 11

Liquefaction - rocks loose strength due to violent shaking and become more liquid than solid.
Landslides and avalanches.
Tsunamis - water above displaced.

Question 12

Key dates of Christchurch 2011

Answer 12

Six earthquakes from 04/09/10 to 23/12/11 from magnitude 5.3 to 7.1.
Feb 22nd 2011 only one causing casualties.

Question 13

Geological and ground conditions of Christchurch

Answer 13

Deep alluvial soils (fine soils) of Canterbury Plains. The area was originally a swamp = sand and silt (soft wet sediment). Shallow soils only 10m thick in some areas, maximum of 40m.
Shallow water table - 5m deep in Western suburbs.

Question 14

Factors increasing risk in Christchurch

Answer 14

Developed country = high repair cost for damages.
Alluvial soils
Abundance of water systems
Flooding river
Densely populated
Multiple earthquakes in a short period of time.

Question 15

Impacts of liquefaction in Christchurch

Answer 15

Extensive damage to properties, lifelines, and infrastructure.
Large volume of sand and silt covering buildings.
Mud and water flooding streets.
Permanent tilt of houses, foundations and structural damages.
Damage to buried pipe networks.
20,000 residential buildings severely affected.
8,000 residential buildings damaged beyond repair.

Question 16

Key dates of Kashmir 2005

Answer 16

October 8th 2005 = magnitude 7.6 earthquake triggering several thousand landslides.
Epicentre near Muzaffarabad, Pakistan.
30-40km from airport.

Question 17

Factors increasing risk in Kashmir

Answer 17

Geology - silt, sandstone, clay, and mudstone. Easily eroded and not condensed, prone to landslides.
Weak rock type.
Shear valleys
Proximity to settlements
Proximity to water sources
Remote location - aid response time.
Level of development.
Steep relief

Question 18

Impacts of landslides in Kashmir

Answer 18

Flooding endangered residents in Hattian village (2.8km downstream).
Damage to bridges
Destroyed houses at or near stream level.

Question 19

Mitigation techniques to minimise impacts in the future.

Answer 19

Flood routing models appropriate to conditions of landslides deposits with an excavated spillway.
Data and construction with field engineers so information can be transferred to people preparing digital evaluation models and other critical data for the landslide dam-breach analysis.

Question 20

Characteristics of Basaltic lava

Answer 20

Low viscosity
Low silica content
Gas escapes
0.5-2% gas
Divergent plate margin
1000-1200 degrees
High eruption frequency
Gentle, effusive eruptions
Shield volcanoes
Low explosivity

Question 21

Characteristics of andesitic lava

Answer 21

Intermediate viscosity
Medium silica content
Traps gas
3-4% gas
Conservative plate margin
800-1000 degrees
Violent, moderate explosive eruptions
Composite volcanoes
Moderate explosivity

Question 22

Characteristics of rhyolitic lava

Answer 22

High viscosity
High silica content
Traps gas
4-6% gas
Conservative plate margin
650-800 degrees
Low eruption frequency
Very violent eruptions
Composite/stato volcano
High explosivity

Question 23

Jökulhlaups (secondary hazard)

Answer 23

Snow and ice in glaciers melt after an eruption which causes sudden floods that are very dangerous.

Question 24

Lava flows (primary hazard)

Answer 24

Streams of lava that have erupted onto the Earth’s surface. Fast flowing lava can be very dangerous depending on it’s viscosity and silica content.

Question 25

Pyroclastic flows (primary hazard)

Answer 25

A mixture of hot, dense rock, ash, lava, and gases which move very quickly along the Earth’s surface. They travel at high speeds, are very dangerous and can cause asphyxiation (lack of oxygen supply) for anyone caught in the flow.

Question 26

Tephra and ash flows (primary hazard)

Answer 26

Pieces of volcanic rock and ash blasted into the air causing damage to buildings, which can collapse under the weight and disruption to flight paths.

Question 27

Volcanic gases (primary hazard)

Answer 27

Gases like sulphur dioxide and carbon monoxide released into the atmosphere. can travel long distances due to their potency.

Question 28

Lahars (secondary hazard)

Answer 28

A combination of rock, mud, and water, which travel quickly down the sides of a volcano. Can occur during the heat of the eruption causing snow and ice to melt or when an eruption coincides with heavy rainfall.

Question 29

Acid rain (secondary hazard)

Answer 29

Gases such as sulphur dioxide are released into the atmosphere.

Question 30

Similarities between lahars and jökulhlaups

Answer 30

Travel at high speeds
Contain water and volcanic material
Pick up material and debris whilst travelling.

Question 31

Example of a jökulhlaup

Answer 31

Eyjafjallajökull 2010 - aah clouds disrupted aeroplanes, changed river channel routes.
Event was anticipated - main road closed and breaches made in road embankment to allow water and deposits to pass through with minimal damage.

Question 32

Example of pyroclastic flow

Answer 32

Chances Peak, Montserrat 1997 - destroyed capital town of Plymouth

Question 33

Example of flank fissure

Answer 33

Nyiragingo volcano, 1977 - lava bombs, flank fissure drained lava lake in under an hour. Swamped several villages killing many. Occurred at night = people asleep, unprepared, no evacuation.
Quick onset = velocity of 20-60km/hr for 9km.

Question 34

Flank fissure

Answer 34

The release of lava and pyroclastic material from a source on the slopes of a volcano instead of it’s primary central vent.

Question 35

Example of tephra

Answer 35

Eyjafjalljökull, 2010 - ash cloud present over trans-Atlantic flight path, disrupted aircraft movement for a week.
Local evacuations of 700 people.
Closure of main road due to poor visibility.

Question 36

Example of volcanic gas

Answer 36

Mount Pinatubo, 1991 - produced a 20 million ton sulphur dioxide cloud. 32km high and cooled the Earth for around 3 years by 0.6 degrees.

Question 37

Tectonic setting of Iceland

Answer 37

North Atlantic Ridge, divergent plate margin (constructive). 30+ active volcanic systems, eruptions 3-5 years, many under ice caps.

Question 38

Key details of Eyjafjallajökull eruption 2010

Answer 38

Moderately active ice-capped volcano, 18 years of intermittent volcanic unrest.
20th March to 12th April 2010 = effusive lava eruption
14th April to 22nd May 2010 = explosive summit eruption

Question 39

Management before the Icelandic 2010 eruption

Answer 39

Signs of renewed activity at the beginning of 2010 - authorities prepared for potential eruption.
Full scale evacuation tested in 2006 by the Icelandic department of Civil Protection and Emergency Management (ICP).

Question 40

Management during the Icelandic 2010 eruption.

Answer 40

Immediate activation of the ICP system (emergency phase) - highest priority activation orders and red cross emergency shelters set up.
Temporary service shelters for locals set up by ICP.
Farmers allowed to go into hazard zones for 2 hours to tend to livestock (created good relationship between locals and authority).
47% didn’t evacuate as they had livestock or elderly to look after.

Question 41

Impacts of the Icelandic eruption

Answer 41

Flood outburst = roads closed and access restrictions around eruption site.
Dense ash = difficulty seeing and breathing.
Ash cloud caused international flights to be stopped across Iceland and Europe.
No deaths, or injuries due to most residents evacuating when asked.

Question 42

Social impacts of Iceland 2010

Answer 42

Shift in European regulation and risk management.
Disrupted 10 million people.
Short term health problems from ash cloud = asthma, mental distress, anxiety amongst kids.
Long term health problems = skin rash, back pain, insomnia.
2 indirect deaths from hypothermia.

Question 43

Economic impacts from Iceland 2010

Answer 43

Disruption to aircraft (biggest since WW2) - worldwide loss of €3.75 billion.
Due to increased media exposure, Iceland’s tourism industry became their biggest economic contributor, growing 20% each year until 2020.

Question 44

Indian Ocean Tsunami 2004 - short term impacts

Answer 44

Social - Andaman and Nicobar cut off as jetties were destroyed. Some villages 70% killed, 50 million affected, 300,000 died.

Question 45

Indian Ocean Tsunami 2004 - mid term impacts

Answer 45

Environmental - most vegetation and topsoil removed up to 800m inland.

Economic - Sri Lanka had 60% of it’s fishing fleet and industrial infrastructure destroyed.

Social - Sumatra had 1,500 villages destroyed. Economies devastated and thousands lost their jobs.

Question 46

Indian Ocean Tsunami 2004 - long term impacts

Answer 46

Environmental - Fresh water supplies and agricultural soil contaminated by saltwater. Ecosystems (coral reefs, mangroves, forests, wetlands) severely damaged.

Economic - Thailand, tourism industry lost around $25 million a month and 120,000 workers lost their jobs.

Social - 1.7 million homeless.

Question 47

Indian Ocean Tsunami 2004

Answer 47

The deadliest tsunami recorded in history. Global volume of aid and relief provided to the affected developing countries was larger than ever before.

Question 48

How is a tsunami formed?

Answer 48

Usually caused be an underwater earthquake or volcanic eruptions. Tend to occur along plate boundaries.

A displacement of a large area of the seafloor causes a displacement of the water column above. Waves radiate from the source in all directions.

The nature of tsunami waves will depend on: the cause of the wave (earthquake or eruption), distance travelled from source (energy lost), water depth, offshore topography.

As water shallows, wave slow down and increase in height to produce onshore waves of up to 30m high.

Sea-floor irregularities reflect some wave energy so less reaches the coast.

Forth or fifth wave is usually the biggest wave, 40% of the wave energy is scattered back to sea and 60% is expended at or near the coast.

Death and destruction will depend on land uses, population density, and warning given.