Tectonic Processes And Hazards

Question 1

Mantle

Answer 1

A solid that generates huge amounts of heat which flow towards the earth’s surface. It’s a solid, but because of the very high temperatures present it is deformable / plastic, and capable of a very high flow.

Question 2

Mantle Plumes

Answer 2

Concentrated areas of heat convection. At plate boundaries they are sheet-like, whereas at hot spots they are column-like.

Question 3

Radioactive Isotopes in the Mantle

Answer 3

Uranium-238 and Thorium-232

Question 4

Oceanic Plates

Answer 4

High Density, basaltic rock but only 7-10 km thick

Question 5

Continental Plates

Answer 5

Thicker at 25-70km, but made of less dense granitic rock

Question 6

Locations of mid-plate hotspots

Answer 6

Hawaii and the Galápagos Islands

Question 7

Divergent Oceanic - Oceanic Example

Answer 7

Mid-Atlantic Ridge in Iceland

Question 8

Divergent Oceanic - Oceanic Description and Hazards

Answer 8

Rising convection currents bring magma to the surface resulting in small basaltic eruption, creating new oceanic plate. Minor, shallow earthquakes

Question 9

Divergent Continental - Continental example

Answer 9

African Rift Valley / Red Sea

Question 10

Divergent Continental - Continental Description and Hazards

Answer 10

Caused by a geologically recent mantle plume splitting a continental plate to create a new ocean basin. Basaltic volcanoes and minor earthquakes

Question 11

Convergent Continent-Continent example

Answer 11

Himalayas

Question 12

Convergent Continental - Continental Description and Hazards

Answer 12

The collision of the continental landmasses creating a mountain belt as the landmasses crumple. Infrequent major earthquakes distributed over a wide area

Question 13

Convergent Oceanic - Oceanic Example

Answer 13

Aleutian Islands, Alaska

Question 14

Convergent Oceanic - Oceanic Description and Hazards

Answer 14

One oceanic plate is subducted beneath another, generating frequent earthquakes and a curving chain of volcanic islands

Question 15

Convergent Oceanic - Continental Example

Answer 15

Andean Mountains

Question 16

Convergent Oceanic - Continental Description and Hazards

Answer 16

An oceanic plate is subducted under a continental plate, creating a volcanic mountain range, frequent large earthquakes and violent eruptions.

Question 17

Conservative Oceanic-Continental Example

Answer 17

California, San Andreas Fault zone

Question 18

Conservative Oceanic-Continent Description and Hazards

Answer 18

Plates slide past each other, along zones known as transform faults. Frequent, shallow earthquakes but no volcanic activity

Question 19

Subduction

Answer 19

The process of one plate sinking beneath another at a convergent boundary

Question 20

Gravitational Sliding

Answer 20

Constructive margins have elevated altitudes because of the rising heat beneath them, which creates a slope down which oceanic plates slide

Question 21

Slab Pull

Answer 21

Cold, density of the oceanic plate pulls itself into the mantle

Question 22

Benioff Zone

Answer 22

A range of focal depths from 10km to 400km, following the line of the subducting plate. It can yield very large earthquakes up to magnitude 9.0.

Question 23

Wet Partial Melting

Answer 23

Plates melt generating magma with a high gas a slice content, which erupts with explosive force.

Question 24

Examples of Collision Zones

Answer 24

Himalaya Mountains (boundary between Indo-Australian planet and Eurasian)

Kashmir 2005

Nepal 2015

Question 25

P-Waves / Primary Waves

Answer 25

The fasted seismic waves. They arrive first, and cause the least damage.

Question 26

S-Waves / Secondary Waves

Answer 26

Arrive second and shake the ground violently, causing damage

Question 27

L-Waves / Love Waves

Answer 27

Arrive Last as they travel only across the surface. However, they have a large amplitude and cause significant damage, including fracturing the ground surface.

Question 28

Crustal Fracturing in Earthquakes Example

Answer 28

Indian Ocean Tsunami 2004; ruptured a fault line for up to 1000km

Question 29

Landslide Example

Answer 29

Landslides accounted for up to 30% of deaths in the 2008 Sichuan and 2005 Kashmir Earthquakes.

Question 30

Focus

Answer 30

The origin of an earthquake

Question 31

Epicentre

Answer 31

The point on the Earth’s surface directly above the focus.

Question 32

Liquefaction

Answer 32

Intense Earthquake shaking compacts the loose sediment together, rocking water between the sediment out and upward. This undermines foundations and causes buildings to sink, tilt and often collapse.

Question 33

Lava flow

Answer 33

Extensive areas of solidified lava, which can extend several kilometres from volcanic vents if the lava is basaltic and low viscosity. It can flown at up to 40km/h

Question 34

Pyroclastic flow

Answer 34

Very large dense clouds of hot ash and gas at temperatures of up to 600 degrees. They can flow down the flanks of volcanoes and devastate large areas.

Question 35

Ash Fall

Answer 35

Ash particles, and larger tephra particles, can. Blanket huge areas in ash,killing vegetation, collapsing buildings and poisoning water courses

Question 36

Gas Eruption

Answer 36

The eruption of carbon dioxide and sulphur dioxide, which can poison people and animals in extreme cases

Question 37

Lahar

Answer 37

Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction

Question 38

Jökuhlaup

Answer 38

Devastating floods caused when volcanoes erupt beneath glaciers and ice caps, creating huge volumes of meltwater. They are common in Iceland

Question 39

Volcano type where lava flow occurs

Answer 39

Composite at a subduction zone and Shield at a hot-spot

Question 40

Volcano Type where Pyroclastic Flow occurs

Answer 40

Composite at subduction zone

Question 41

Volcano Type where Ash Fall Occurs

Answer 41

Cinder Cone / Fissure Eruption at constructive margin and Composite at subduction zone

Question 42

Volcano Type where Gas eruptions occur

Answer 42

Composite at subduction zone and Shield at hot-spot

Question 43

Volcano Type where Lahar occurs

Answer 43

Composite at Subduction zone

Question 44

Volcano Type where jökulhlaup occurs

Answer 44

Cinder Cone / Fissure Eruption at constructive plate margin

Question 45

The 4 deadly tsunamis since 2004

Answer 45

2004 Indian Ocean, 2006 Java Indonesia, 2009 Samoa, 2011 Japan

Question 46

2004 Indian Ocean Tsunami

Answer 46

9.2 Magnitude, 24m high waves, 230 000 deaths

Question 47

2006 Java, Indonesia Tsunami

Answer 47

7.7 Magnitude, 2-6m high waves, 800 deaths

Question 48

2009 Samoa Tsunami

Answer 48

8.1 Magnitude, 14m high waves, 190 deaths

Question 49

2011 Japan Tsunami

Answer 49

9.0 Magnitude, 9.3m high waves, 16 000 deaths

Question 50

Tsunami Formation

Answer 50

A sub-marine earthquake displaces the sea bed vertically as a result of movement along a fault line at a subduction zone. The violent motion displaces a large volume of water in the ocean water column, which then moves outward in all directions from the point of displacement. The water moves as a vast bulge in open water, rather than as a distinct wave.

Question 51

Characteristics of a Tsunami in open ocean

Answer 51

A wave hight of less than 1m, wavelength of more than 100km, speeds of 500 - 950 km/h

Question 52

Threshold

Answer 52

The magnitude above which a disaster occurs. This threshold level could be different in developed countries vs a developing country because of different levels of resilience

Question 53

Hazard Risk Equation

Answer 53

Risk = (hazard x vulnerability) / capacity to cope

Question 54

Characteristics of a Country with a high capacity to cope and high resilience

Answer 54

Emergency Evacuation, rescue and relief systems are in place. They react by helping each other to reduce numbers affected. Hazard-Resistant design or land use planning have reduced the numbers at risk.

Question 55

Pressure and Release Model Example

Answer 55

2010 Port-au-Prince earthquake in Haiti. It’s magnitude of 7.0 was relatively low, but the death toll has been estimated at 160,000.

Question 56

Root Causes in the Pressure and Release Model

Answer 56

Low access to resources, limited influence in decision making, poor governance and a weak economic system

Question 57

Dynamic Pressures in the Pressure and Release Model

Answer 57

Lack of education training and investment, rapid population change and urbanisation

Question 58

Unsafe Conditions in the Pressure and Release Model

Answer 58

Poor construction standards, unsafe infrastructure, poverty, lack of social safety net

Question 59

The PAR model applied to the Haiti Earthquake

Answer 59

GPD = US$1200, 70% of jobs in the informal sector, 25% living in extreme poverty, 50% under 20 years old, no sewer system, 80% of housing is unplanned, informal slums

Question 60

Resilience

Answer 60

The ability of a community to cope with a hazard; some communities are better prepared than others so a hazard is less likely to become a disaster

Question 61

Social Impacts of Tectonic Hazards

Answer 61

Deaths, injury and wider health impacts including psychological ones

Question 62

Economic Impacts of tectonic hazards

Answer 62

The loss of property, business, infrastructure and opportunity