On completion of this module, you should be able to:

1. Articulate the evidence for, and uncertainties around, the deep structure of Planet Earth

2. Explain the basic principles of geophysical phenomena such as seismic waves, geomagnetism, gravity, and geothermal heat.

3. Explain how tectonic plates move, how this can be measured and what factors control it.

4. Recognise the main brittle and ductile geological structures and articulate how they relate to tectonic processes.

5. Represent and analyse geological/geophysical data in 2D and 3D.

6. Conduct and present independent research into the geotectonic characteristics of anywhere on Earth.

7. Use a simple Geographical Information System (GIS) software (GeoMapApp) to access and visualise online geodata resources (e.g. United States Geological Survey Earthquake catalogue, Global CMT moment tensor catalogue, Bureau Gravimetric International, UNAVCO GPS data sets, etc.)

Lectures (1 hour)


(1) Earth Structure (A Seismic Journey to the Centre of the Earth)
I. Lokmer

How the reflection and refraction of seismic waves, combined with Earth’s gravity, rotation and with information from meteorites, can illuminate the deep compositional and mechanical structure of the Earth. Concepts of the Crust, Moho, Mantle, Core, Mohorovičić Discontinuity (MOHO), Gutenberg Discontinuity, Lehman Discontinuity.

(2) Earth in Motion: Basis for Plate Tectonics
I. Lokmer

Origin of heat in the Earth. Temperature distribution in the Earth: geotherms. How seismic wave tomography can provide an ‘x-ray scan’ of the deep thermal structure of the Earth. Concepts of mantle convection and mantle plumes.

(3) Earthquakes
I. Lokmer

Why and how earthquakes occur. Rheology: brittle vs. ductile deformation. How deep earthquakes occur. Main types of seismic waves: P, S, Rayleigh and Love waves. Locating and measuring earthquake size. Earthquake magnitude and seismic moment.

(4) Earthquake radiation and source mechanism
I. Lokmer

How is the earthquake mechanism determined from seismograms? Fault plane solution, beachballs. Spatial distribution of earthquake source mechanisms around the globe.

(5) Gutenberg-Richter Relationship and Power Law of Other Natural Phenomena
I. Lokmer

An overview of how many natural phenomena, such as earthquakes, floods, volcanic eruptions, rivers/stream lengths etc., exhibit power-law relationships.

(6) Earth’s Magnetic Field
I. Lokmer

The nature and origin of the Earth’s magnetic field. Concept of the geodynamo.

(7) Earth’s Shape and Gravity
E. Holohan

Introduction to geodesy. Gravitational attraction and the concept of the geoid. The ‘deflection of the vertical’. Types of gravity anomalies - Free Air Anomaly, Bouguer Anomaly, Isostatic Anomaly. Correlation (or not) between gravity anomalies and main physiographic features of the Earth. Global Navigation Satellite Systems (GNSS) - a.k.a. GPS.

(8) Do Continents Float?
E. Holohan

Types and densities of rocks found on continents and under oceans. Concept of Isostasy. Airy and Pratt models of isostasy as applied to explain relationships between the Earth’s topography, bathymetry and crustal structure. Limitations of simple isostatic models of the Earth’s shallow structure.

(9) Flexing the Earth
E. Holohan

Evidence for flexure of the Earth’s crust by large volcanoes. Concepts of the rigid, strong Lithosphere and the soft, weak Asthenosphere. Seismic evidence for their lower limits. Is the L-A-B thermally controlled? Flexural-isostatic consequences of the growth and retreat of ice sheets.

(10) Drifting Continents?
E. Holohan

An overview of the development of the modern concept of plate tectonics. Geological evidence behind Wegener’s theory of unfixed continents. Paleomagnetism. Evidence for seafloor spreading and continental wandering. Evidence from oceanic rock dating and drilling. Hot-spot tracks. Evidence for subduction zones. Confirmation by modern GPS.

(11) Moving Plates on a Sphere
E. Holohan

Manner and mechanisms of tectonic plate motion. Euler poles, relative angular velocity and relative linear velocity. Why do some plates move faster than others? Mantle drag vs. Edge force. Slab pull and ridge push. Links (or not) to mantle convection.

(12) Plate boundaries and relative motion
E. Holohan

Nature and stability of plate boundaries and junctions. Velocity analysis. Triple and quadruple junctions. Migration of triple junctions. Application to Alpine Fault of New Zealand and San Andreas Fault system of California.

(13) Tectonic Plates: Dividing
J. Walsh

Plate break up (‘rifting’) and the anatomy of divergent plate margins. Concepts of lithospheric thinning, decompression melting and rift-related volcanism. Failed rifts and ‘Passive’ continental margins. Main structural and physiographic features of mid-ocean ridges.

(14) Tectonic Plates: Sliding
J. Walsh - 17.00, Thursday 5th of November
Transform/strike-slip plate margins. Pull-apart basins and pop-up mountains.

(15) Tectonic Plates: Colliding
J. Walsh

‘Active’ collisional continental margins and the anatomy of subduction zones. The formation of back-arc basins. Continent-continent collisions and the anatomy of orogenic belts

(16) Rock Deformation and Earthquakes
J. Walsh

An overview of laboratory tests on how rocks deform. Key concepts of rock strength and brittle vs. ductile behaviour. Effects of confining pressure, temperature, mineralogy, strain rate, fluids and anisotropy. Implications for earthquake distribution in the Earth.

(17) Brittle Geological Structures
J. Walsh

Recap of Anderson theory of faulting. Fault rocks and slip sense indicators. Fault systems and relationship to tectonic settings. Magmatic dykes, hydro-fractures and relationship to tectonics.

(18) Ductile Geological Structures
J. Walsh

Folds, boudinage and shear zones. Wavelength, Amplitude, and Interference of Folds. Relationship of ductile structures to tectonic setting.

(19) The Lithosphere: Creme Brulee or Jelly Sandwich?
E. Holohan

Types and properties of rocks in the oceanic vs continental lithosphere. Friction vs Viscosity as a description of lithospheric strength. Relationship between strength and mineralogy and rigidity (flexure). Creme Brulee vs Jelly (Jam) Sandwich models for lithosphere structure (strength).

(20) Plates vs. Plumes: the Limits of Plate Tectonic Theory.
E. Holohan

Aspects of Earth’s deep structure and surface morphology unexplained by classic, rigid-plate tectonic theory. Intraplate earthquakes, diffuse crustal deformation, slab roll-back, intraplate volcanism (‘hot-spots’), intraplate swells.


Practical Classes (2 hours)

Note: These will be given FACE-TO-FACE in Room G01, UCD Science Centre West.


(1) Distribution of Earthquake Magnitudes
I. Lokmer

Examination of Gutenberg-Richter scaling for earthquakes and issue of data completeness. Data analysis in Microsoft Excel.


(2) Earthquakes and Beachballs
I. Lokmer

How to construct and read earthquake focal mechanism solutions (a.k.a. ‘beachballs’), so as to infer the orientation and type of geological fault(s) responsible for producing an earthquake.

(3) Earthquake source mechanisms, fault size and released energy
I. Lokmer

A set of questions on: (i) Inferring a geological scenario from the beachballs at a given geographical region, (ii) Sketching the beachballs given faulting parameters (strike, dip and rake), (iii) Relationship between the size of an active fault, earthquake energy, magnitude and seismic moment.

(4) Gravity and Crustal Thickness of Europe
E. Holohan

Introduction to a simple GIS (GeoMapApp) for accessing and plotting geodata. Produce maps and profiles to show the variation of topography/bathymetry and gravity anomalies across Europe. Make a map of crustal thickness as determined by seismic refraction. Are the observed patterns compatible with Pratt and/or Airy models of isostasy?

(5) Pacific Plate Motion – part 1
E. Holohan
Mapping the relationship between volcano age and sea-floor age in the Pacific Ocean. Using the Hawaii-Emperor hot-spot chain to calculate the long-term linear velocity of the Pacific plate. Has the Pacific plate slowed down or sped up?

(6) Pacific Plate Motion – part 2
E. Holohan
Plotting modern-day velocity vector for the Hawaiian plate as determined by GPS measurements. How does this compare to long-term velocity estimated in Part 1? Using additional data from the Cobb and Louisville hotspot tracks, where might the Euler pole of the Pacific plate be?

(7) Ocean Spreading
E. Holohan
Using maps and profiles of sea-floor age to determine the onset and rate of the opening of the South Atlantic Ocean. Work out the relative velocity of divergence between the African and South American plates. Consider how and why this varies along the spreading ridge. Do similar for the South Indian Ocean. Are plate spreading rates constant in time?

(8) Sumatra-Java collisional margin
E. Holohan

Use earthquake locations (hypocentres) to infer the 3D geometry of the Sumatra-Java subduction zone. Consideration of the nature and distribution of earthquakes as indicated by focal mechanism solutions.

(9) Research Assignment Work
E. Holohan

Class time for working on your individual research assignment. Guidance on relevance of data and plotting/visualisation. Troubleshooting any technical issues with GeoMapApp or Excel. Discussion of your initial research findings.

(10) Research Assignment Work
E. Holohan

Class time for working on your individual research assignment. Guidance on relevance of data and plotting/visualisation. Troubleshooting any technical issues with GeoMapApp or Excel. Discussion of your initial research findings.

Not applicable to this module.

• Feedback individually to students, on an activity or draft prior to summative assessment
• Feedback individually to students, post-assessment
• Group/class feedback, post-assessment
• Peer review activities

Feedback will be provided on a weekly basis and will take the form of: (1) Oral feedback on activities prior to assessment (2) Oral and written post-assessment feedback individually to students and to the class as a whole; (3) Self-assessment and peer-review activities related to projects and presentations.