Geology and Natural Hazards Week 1-2

Week 1 - Lectures 1 & 2 - 12 Aug 2024

• Topography of Earth is more dynamic and active than Mars, with its crust being more plastic and deforming more readily.
• Natural hazards are increasing due to the exponential growth of the global human population.
• Human population growth, increased life expectancy, and efficient food production are linked to improved science and technology.
• Everyday geological processes and interactions between spheres (hydrosphere, biosphere, etc.) contribute to natural disasters.
• Human impact plays a role in the size and location of events. More people and buildings lead to more damage and casualties.
• Catastrophe predictions are possible but challenging, with unpredictable cycles and many variables.
• Recurrence interval increases linearly on a log scale and exponentially on a linear scale.
• Magnitude is inversely proportional to frequency.

Week 2 - Lecture 3 - 19 Aug 2024

• Earth's structure has unique chemical compositions and physical states impacting surface life.
• Plate tectonics theory explains how major landforms are created from lithosphere movements.
• Continental drift (1912) describes continents moving over geologic time.
• Magnetic anomalies are evident in the Earth's magnetic field and its periodic reversals.

Week 2 - Lecture 3 - 19 Aug 2024 (cont.)

• Divergent boundaries occur where plates move apart.
• Convergent boundaries occur where plates collide, leading to subduction and mountain building.
• Transform boundaries involve plates sliding past each other, causing earthquakes.

Week 3 - Lecture 4 - 26 Aug 2024

• Stress and strain cause earthquakes.
• Elastic deformation (reversible) and plastic deformation (not reversible) describe rock behaviour.
• Elastic rebound theory explains energy release during earthquakes.
• Seismic waves (body waves: P and S waves; surface waves: Rayleigh and Love waves) propagate during earthquakes.

Week 3 - Lecture 4 - 26 Aug 2024 (cont'd)

• Different fault types (normal, reverse/thrust, strike-slip) relate to various geological environments (convergent, divergent and transform environments).
• Magnitude of earthquakes is measured using seismic moment (related to length, width and slip of rupture x shear modulus).

Week 4 - Lecture 5 - 2 Sep 2024

• Ground failure (fault rupture, landslides, liquefaction) are earthquake hazards.
• Ground shaking is an adverse effect of earthquakes, with devastating impacts depending on the distance from the source.
• Surface faulting results in visible offsets and is a hazard to structures.
• Earthquakes can trigger landslides, affecting populated regions.

Week 4 - Lecture 5 - 2 Sep 2024 (cont'd)

• Flooding due to landslides impacting water bodies can generate a disastrous situation.
• Liquefaction, a ground failure, involves saturated, loosely packed soils becoming fluid during earthquakes.
• The effect of earthquakes on changes in land level and shoreline is considerable.

Week 5 - Lecture 6 - 9 Sep 2024

• Tsunamis are generated by vertical deformation/movement from earthquakes.
• Tsumanis have very large wavelengths and wave heights, which lead to significant damages and harm in coastal areas.
• Tsunami wave speed is controlled by water depth, causing faster waves in deep water and slower waves in shallow water.

Week 5 - Lecture 6 - 9 Sep 2024 (cont'd)

• Factors influencing tsunami wave height include earthquake magnitude (greater magnitude - larger tsunami); area of rupture and rate of water displacement.
• Underwater ruptures of normal faults, thrust faults and megathrust faults are significant sources for tsunamis.

Week 6- Lecture 7 - 16 Sep 2024

• Different types of volcanoes (shield volcanoes, stratovolcanoes, cinder cones and Calderas) have different eruptive styles.
• Explosive volcanic eruptions can lead to dangerous pyroclastic flows, ash falls, and lahars, which have widespread effects.
• Volcanic eruptions can cause changes to topography and bathymetry.

Week 6 - Lecture 7 - 16 Sep 2024 (cont'd)

• Volcanic eruptions can cause changes to topography and bathymetry.
• Types of magma (basaltic, andesitic, rhyolitic) have different compositions, viscosity, and temperatures which affect eruptive styles.

Week 7 - Lecture 8 - 23 Sep 2024

• Volcanic hazards occur without eruptions (e.g. ground shaking, fractures and fissures)
• Gases released during volcanoes and volcanic activities could cause harm to humans and animals through CO2 suffocation

Week 7 - Lecture 8 - 23 Sep 2024 (cont'd)

• Volcanic hazards include volcanic mudslides (lahars) and landslides, which can result in considerable losses and harms.
• Monitoring volcanic activity helps to predict eruptions and mitigate related risks.

Week 8- Lecture 9 - 7 Oct 2024

• Landslides are the downslope movement of rock, debris and/or mud, depending on the slope angle, moisture content, water saturation and external factors like earthquakes/explosions.
• Rotational and translational slides are different types of landslide movements.

Week 8 - Lecture 9 - 7 Oct 2024 (cont'd)

• The processes involve the interplay of driving forces (gravity) and resisting forces (cohesion, friction and strength of materials).
• Landslides can result in different damages depending on the driving force, the angle of repose, and external factors.
• Types of monitoring/mitigation strategies for landslides are also included

Week 9 - Lecture 10 - 14 Oct 2024

• Delta regions are typically located where rivers enter oceans, seas or lakes.
• The factors causing people to choose to live in delta regions include the flat terrain (for easy transport, farming), and fresh water
• Deltas develop over time, as rivers carry sediment.
• The rising of sea level will threaten delta regions and lead to various impacts on people and their livelihoods.

Week 9 - Lecture 10 - 14 Oct 2024 (cont.)

• Rising sea levels are a global concern, caused by various factors (e.g., glacial melt, thermal expansion of seawater).
• Sea levels are rising leading to floods and the salinization of fresh water resources from the aquifers near the coasts in the delta regions.

Week 10- Lecture 11 - 21 Oct 2024

• Cyclones are rotating storms that derive energy from warm ocean water.
• Warm water, strong winds, and latent heat of vaporisation from oceans are essential for cyclone formation.
• Cyclones develop in tropical and subtropical areas of oceans near the equator.

Week 10 - Lecture 11 - 21 Oct 2024 (cont.)

• Cyclones are associated with strong winds (that can damage infrastructure, knock down buildings etc), heavy rainfall (that can lead to flooding), storm surges (which push ocean water onto coastal areas).
• The Coriolis effect influences the rotational direction of cyclones in different hemispheres
• Cyclones (e.g. hurricanes, typhoons) can cause wide-ranging damages, including death, injuries, building destruction, infrastructure damage (for example, knocking down buildings) and substantial economic losses.

Week 11/12 - Lecture 12 - 28 Oct 2024 / 4 Nov 2024

• Climate change is the long-term shift of weather that affects various aspects of the Earth's system, including atmosphere, hydrosphere, geosphere, biosphere, and cryosphere.
• Variations in Earth's orbit affect solar radiation receipt, which in turn leads to temperature variations.
• Greenhouse gases trap heat radiated from the Earth, warming the planet. Human activities are major contributors, especially burning fossil fuels.

Week 11-12 - Lecture 12 - 28 Oct 2024 / 4 Nov 2024 (cont.)

• Natural factors (e.g., volcanic eruptions and Milankovitch cycles) can also influence climate.
• Increased greenhouse gases and their warming effects have global consequences, including rising sea levels, more extreme weather events, and threats to human societies.
• Monitoring and measuring climate conditions include methods like analyses of ice cores, tree rings and sediments, which can provide insights into past climate conditions.

Week 11/12 - Lecture 12 - 28 Oct 2024 / 4 Nov 2024 (cont.)

• The idea of geoengineering addresses ways to manage the direct consequences of climate change.
• Geoengineering approaches attempt to physically manipulate the Earth's environment to reduce global warming, such as increasing reflectivity of clouds, promoting plant growth, or capturing CO2 from the atmosphere.