Tectonics

Flashcards covering key concepts related to tectonic hazards, volcanoes, earthquakes, and disaster management strategies.

What are the three main layers of the Earth's structure?

Crust, Mantle, and Core (Outer and Inner)

Describe the composition and state of the Earth's mantle.

Molten silicate rocks, iron, magnesium, semi-liquid, including the solid asthenosphere.

What are the three types of plate boundaries and their movements?

Convergent (push into each other), Divergent (pull away), and Conservative (slide against each other)

Give an example of a Continent-Continent Convergent Plate Boundary.

Himalayas, formed by the Indian/Eurasian plate collision

What is the driving mechanism behind plate movement according to the Convection Theory?

Convection currents in the mantle, driven by internal heating of the inner core.

Describe 'ridge push' and 'slab pull' in the context of plate tectonics.

Ridge push: rising mantle pushes plates apart. Slab pull: sinking denser crust pulls down the plate.

What are hotspots and where do they occur?

Areas of volcanic activity away from plate boundaries, often with high heat flow (e.g., Hawaiian Islands, Yellowstone).

How do divergent boundaries on ocean ridges cause earthquakes?

Shallow earthquakes due to shakes from volcanic eruptions.

What are intraplate earthquakes?

Earthquakes caused by the breakage of crust within plates, often due to isostatic recoil.

What human activity was mentioned that can cause earthquakes?

Fracking for oil and gases (Quasi Natural Earthquakes)

What occurs at convergent boundaries and causes volcanoes?

Oceanic plate subducts, melts, and magma rises, leading to violent volcanic activity.

What affects the magnitude of a tectonic hazard event?

It is impacted primarily by quantifiable variable, its size and physical force.

What scale measures the magnitude of volcanic eruptions?

Volcanic Explosivity Index (VEI)

What is the correlation between the scale of magnitude and frequency?

The larger the magnitude, the lower the frequency.

Name the parameters of Hazard Profile.

Predictability, Frequency, Duration, Speed of Onset, Areal Extent and Magnitude

Name three volcano types.

Fissure, Shield, Composite, Acid/Dome, Ash/Cinder, Calderas

What are the two types of explosion classifications?

Effusive and explosive.

What is the greatest cause of volcanic deaths?

Pyroclastic surges.

Why can lava domes be very dangerous

Main summit blocked by thick magma creates Pelean eruptions close to the ground

What is the difference between Pahoehoe and A’a lava?

Pahoehoe is wrinkly and liquid (15 m/s). A’a forms blocks and moves slowly downhill.

What are some of the threats posed by tephra?

Blanket landscape, contaminate farmland and rivers, health issues, damage roofs, conduct electricity, clog air filters, poor visibility.

Which volcanic hazard is the greatest risk to human life, and how does it form?

Lahars (volcanic mudflow/water flow), combining with torrential rain.

What are Jökulhlaups and where are they common?

Violent floods from melting ice trapped between a volcano and glacier, common in Iceland.

What produces shockwaves felt during an earthquake?

Fault movement on fractures/faults causing elastic rebound.

Define the terms 'focus' and 'epicenter' in relation to earthquakes.

Focus: point of pressure break.
Epicenter: point on the surface directly above the focus.

Name 3 types of seismic waves.

P,S, L/R.

Which seismic waves are more destructive?

S & L/R waves.

What is the most severe threat to people during an earthquake?

Ground movement/shaking.

What is liquefaction, and what causes it?

Water-saturated material loses strength and behaves as fluid due to ground shaking.

What factor significantly influences tsunamis?

Fetch

What is Degg's Model

Hazard vs Vulnerability overlap.

Define Vulnerability.

high rate of exposure to a hazard with the inability to cope

What is the population level consideration?

Istanbul lies on a destructive plate boundary, predicted to have a devastating earthquake in the future due to population of +20 m.n

What are the factors that drive a disaster and vulnerability?

Economic, technological, social, political and geographical factors.

What does the Risk equation state?

(Frequency x Vulnerability level) / Coping Capacity

What are some unpredictability factors?

Caught out by timing or magnitude of hazards, White Island UC, New Zealand 2019, NvD

What are PAR model factors?

Intrinsic physical property of a hazard profile can develop a hazard, but the extrinsic/local areal factors that impact communities turn the hazard into a disaster

Name some factors that can cause people to have Hazard perception

Do not believe in the likelihood of the hazard occurring or that they live in a hazardous area eg. LA and Pompeii

List different ways to detect Earthquakes/Tsunamis.

Foreshocks, Geological Changes, Rock Stress.

List different ways to detect Detecting Volcanic Eruptions/Tsunamis

Gas emissions, ground deformation, thermal tracking, mass movements, hydrology, remote sensing, seismic history.

List some examples of resistance technology.

Base isolation, Partial buoyancy, Energy dissipation systems.

Nevado del Ruiz CASE STUDY

• Nov 13, 1985, 9 PM

• Deaths: 25,000, killed 70% of Armero’s population, 5000 injured

• Time: Nov 13, 1985, 9 PM, 

• Duration: 1 day

• Cause: seismic activity and earthquakes going back a year before the eruption

• Primary impacts: large pyroclastic flows/surges and lava

• Secondary impacts: 3 lahars from melted glaciers moving at 30 km, 

• Economic: cost $7.7 b.n, 20% of Colombia’s GNP, regional loss of 60% livestock, 30% grain and rice, and half a million bags of coffee, $218 m.n loss

• Social: 10,000 homeless people, destruction of 50 schools, 2 hospitals and homes

• Environmental: acid emissions contaminating soil and rivers, pyroclastic flow contaminating land and rivers, little on farmland, damage restricted to ecosystems on the mountain edge

• Volcano/eruption type, Plates: Composite volcano, explosive type, 3 Plinian eruptions, Nazca and Pacific plates

• Preparation: insufficient, lack of seismographs placed inadequately, communication with Armero broke down, no evacuation

• Post Eruption: better preparation and seismographs, improved regional volcanology, successful evacuation of 4000 in 2016 eruption

E15 CASE STUDY

• 11:52 PM March 20 2010

• Deaths: 0

• Time: 11:52 PM March 20 2010

• Duration: 39 days

• Cause: seismic activity causing glacial ice to melt

• Primary impacts: ash tephra covering the sun, jökulhlaups 

• Secondary impacts: ---

• Economic:  Eurostar gained 50,000 passengers, airlines lost ~$20 mn. Per day, 

• Social: 10mn. Airline passengers affected by ash tephra, 

• Environmental: 0.15 M CO2 added to the environment, phytoplankton blooms due to ash tephra, halt in ir traffic so prevented 2.8 mn tonnes of CO2 emissions

• Volcano/eruption type, Plates: Composite volcano, North American and Eurasian plates, divergent, effusive eruption

• Preparation: immediate evacuation of 800 people, 

• Post Eruption: text message warning system in place, more earthquake monitoring devices

MOUNT NYIRAGONGO DRC CASE STUDY

• 08:25, 17 Jan 2002

• Deaths: 200 deaths

• Time: 08:25, 17 Jan 2002

• Duration: 12 hours

• Cause: seismic activity and plate fractures in Lake Kivu 

• Primary impacts: basaltic lava, carbon monoxide accumulation

• Secondary impacts: acid rain

• Economic: received internationally $35 mn., 95% unemployment, wage depression due to loss in rent

• Social: 12,500 homes destroyed, one third of Goma city destroyed, destruction of shops and businesses, looting broke out

• Environmental: 147 kt/day of SO2, 9.3 kt/d of CO2

• Volcano/eruption type, Plates: Composite volcano, divergent plates, african into nubian plate, effusive eruption

• Preparation: 400,000 people evacuated, limited evacuation, people went to see the eruption, 50,000 people were trapped between two lava flows

• Post Eruption: destruction of airports disrupted international aid

PORT AU PRINCE HAITI CASE STUDY

• 4:53 PM, January 12, 2010

• Not well developed

• GDP growth support by mining sector (cobalt, other minerals)

• Mining contributes to 70% growth in 2023

• Agriculture employs 60% workforce

• Governance is both state and local

• State governance is more accessible, local leaders more traditional and isolated

• Governance characterised by opacity and corruption

• Crisis began as a result of post-colonial battles, assassination of popular leaders and 30 year dictatorship

• Ethnic tensions in Rwanda

• Congo war of 96-97

• 2nd congo war 98-2003, Rwandan ethnic cleansing

• M23 militia formed

• Education improving, but classes are overcrowded and there are few teachers

• Introduction of free primary education, which means less teachers because they are not paid (as well)

• Depletion of education budgets

• Disease and malnutrition put 4.5 mn children and 3.7 mn pregnant women at risk of mpox

• Inadequate healthcare: limited disease treatments, monitoring and screening centres, depletion of resources, lack of healthcare equipment

TOHOKU JAPAN CASE STUDY

• March 11, 2011

• Deaths: 19, 579

• Time: March 11, 2011

• Magnitude: 9.0 Richter scale

• Impacts: 5000 aftershocks, 39 m high tsunami triggered, 500, 000 people homeless, Shortage of all services, 1 million left without running water, Fukushima nuclear power plant damaged, causing a radiation leak

• Short term: 20 km evacuation zone around the power plant was established, 27 bullet trains stopped within 2 seconds of the earthquake detection, 11 military aircraft sent up to identify cut off communities within half an hour

• Long term: Within 8 months, +95% of infrastructure had been rebuilt, Reconstruction council set up and given 23 trillion yen to rebuild infrastructure, rebound the economy and attract investment

• Mitigation: Seawalls and coastal dikes, Evacuation drills regularly carried out, routes improved, Prearranged agreements to share essential responsibilities, Drones used to locate people