GL5036 Earth Physics, Structure and Processes

GL5035 Earth Physics, Structure and Processes

This course is typically the first course that MSc Geophysics students at the University of Aberdeen take and is designed to help them understand the fundamentals of Earth’s structure and geodynamic processes. Students on the MSc Geophysics come from a diverse range of first degree subjects. This course aims to introduce geological concepts to those from a more physics-based background, and introduce fundamental physics to those from a geology background. It develops their coding skills and gives them experience in reading papers and scientific writing.

Learning objectives
  • Explain how Earth’s structure and processes are governed by the underlying physics
  • Describe how the Earth deforms and the consequences of this on the surface of the Earth
  • Demonstrate fluency in the basic mathematical and coding skills required for subsequent coursework
  • Demonstrate the ability to read scientific papers and gain experience in writing literature reviews
  • Gain experience in giving scientific presentations
Teaching and Learning

Teaching on the MSc Geophysics is typically block teaching: each course is taught over 2 and half weeks with students focussing on just that course. For GL5036 nine topics are covered within the teaching block, typically one a day. For details of the material covered, see below.

Due to the ongoing Covid-19 pandemic and government and university guidelines, teaching for this course took place online in the 2020-2021 academic year. There was a mixture of self-study materials in the form of pre-recorded lectures with questions and two papers per topic (see below for the 2020-21 reading list), and ‘live’ sessions via Blackboard Collaborate. In the live sessions, the lecture materials and questions were reviewed, the reading material was discussed and the computer-based practical exercises were started. Practicals were mainly in the form of Jupyter notebooks.

In addition to three assessed practicals, students wrote a 2500 word essay on a major division in the Earth, discussing it’s geophysical properties, and gave a 15 minute presentation on a basin of their choice.

Level:

MSc Geophysics

When:

1st half session

Teaching:

Lectures, tutorials, computer-based practicals

Course outline 2020-2021

  • Earth as a planet

    • Explain how conservation of energy and angular momentum determine how planets move around the Solar System
    • Understand how the Solar System is likely to have formed
    • Describe key properties of planets, moons and other bodies in the solar system
  • The Internal Structure of the Earth

    • Describe the major divisions in the Earth
    • Describe how seismic velocities, density, pressure and gravity vary with depth in the Earth
    • Understand the techniques that have been used to investigate Earth structure and composition
    • Explain how seismic waves are used to investigate Earth structure
  • Heat

    • Understand some fundamental thermodynamic concepts
    • Apply thermodynamic equations to simple problems
    • Describe how temperatures in the Earth vary
    • Understand how heat is transported in the Earth
    • Describe the sources of heat in the Earth and their relative importance
    • Describe how heat flow is measured and varies on the continents and in the oceans
    • Model how oceanic lithosphere cools and the consequences of this
    • Describe models of convection in the mantle
  • Magnetism

    • Understand some fundamental magnetic concepts including magnetic potential and the magnetic moment.
    • Understand the geometry of Earth’s magnetic field.
    • Explain how the solar wind and the Earth’s magnetic field interact.
    • Describe the nature of the magnetic field generated by the Earth.
    • Explain how the geodynamo works.
    • Describe secular variation to the geomagnetic field.
  • Gravity

    • Describe the gravitational force and acceleration due to mass of the Earth
    • Describe the force and acceleration due to spin of the Earth
    • Understand how measurements of the gravitational field can be used to investigate the physical and environmental properties of a planet
    • Explain how the Earth’s shape is modified by gravitational acceleration.
    • Explain how tides occur
    • Explain how the Earth’s orbit is affected by gravitational attraction of other bodies in the solar system
  • Plate Tectonics

    • Explain what the lithosphere is and how it can be defined.
    • Describe how the Earth’s lithosphere is broken into tectonic plates
    • Describe the observations that lead to the discovery of plate tectonics
    • Describe types of plate boundaries and the geological and geophysical consequences of these boundaries.
    • Understand what drives plate motion
    • Explain the Wilson cycle
    • Understand debates surrounding when plate tectonics initiated on Earth
  • Rheology

    • Explain what stress and strain are, including the components of the stress and strain tenors.
    • Understand different types of deformation that occur in the Earth.
    • Explain how stress and strain are related in elastic, plastic and viscous deformation.
    • Describe solid-state flow and the relative importance of different creep mechanisms
  • Isostasy and Flexure

    • Explain different models for isostatic compensation of topographic loads
    • Describe the effects of flexure in oceanic lithosphere as a result of ocean islands and subduction.
    • Understand how glaciostatic rebound can be used to estimate mantle viscosity.
    • Describe different models for continental lithospheric strength
    • Understand how thermal, compositional, and structural parameters effect the models of strength of the lithosphere.
  • Basin Formation

    • Describe the classification of sedimentary basins.
    • Understand models of how basins are formed though extension
    • Describe how basins are formed and evolve due to flexure in collisional settings.
    • Describe how basins are formed in strike-slip settings.
    • Understand how backstripping can be used to investigate the evolution of a basin.

GL5035 Reading 2020-21

The Earth as a planet

Banerdt et al., (2020) Initial results from the InSight mission on Mars, Nature Geoscience, 13, 183-189

Canup (2012) Forming a Moon with an Earth-like compositon via a Giant Impact, Science, 338, 1052-1054

Internal Structure of the Earth
Heat

Gando et al., (2011) Partial radiogenic heat model for Earth revealed by geoneutrino measurements, Nature Geoscience, 4, 647-651

French and Romanowicz, (2015) Broad plumes rooted at the base of the Earth’s mantle beneath major hotspots, Nature, 525, 95-99

Magnetism

Bono et al., (2019) Young inner core inferred from Ediacaran ultra-low geomagnetic field intensity, Nature Geoscience, 12, 143-147

Aubert and Finlay, (2019) Geomagnetic jerks and rapid hydromagnetic waves focusing at Earth’s core surface, Nature Geoscience, 12, 393-398

Gravity

Sasgen et al., (2020) Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites, Nature Communications Earth and Environment, 1, 1, 1-8

Park et al., (2016) A partially differentiated interior for (1) Ceres deduced from its gravity field and shape , Nature, 537, 1515-517

Plate Tectonics

Heron et al., (2016) Lasting mantle scars lead to perennial plate tectonics, Nature Communications , 7, 1, 1-7

Sobolev and Brown, (2019) Surface erosion events controlled the evolution of plate tectonics on Earth, Nature, 570, 52-57

Rheology

Miyazaki et al., (2013) Olivine crystals align during diffusion creep of Earth’s upper mantle, Nature, 502, 321-326

Ferreira et al., (2019) Ubiquitous lower-mantle anisotropy beneath subduction zones, Nature Geoscience, 12, 4, 301-206

Basin Formation

Péron-Pinvidic and Manatschal (2010) From microcontinents to extensional allochthons: witnesses of how continents rift and break apart?, Petroleum Geoscience, 16, 3, 189-197

Practicals 2020-2021
Seismic Phases

Using a jupyter notebook students are introduced to obspy and using obspy tools investigate the travel times and ray paths for seismic phases. They download seismograms for teleseismic earthquakes and identify seismic phases on record section plots.

Heat flow vs age in the oceans

In this practical students use a jupyter notebook, adapted from Lowrie and Fichtner (2020) Fundamentals of Geophysics, to develop a simple mathematical model for heat flow vs age from data complied by Hasterok et al. (2011).

Tidal acceleration and the Roche limit

Using a jupyter notebook, adapted from Lowrie and Fichtner (2020) Fundamentals of Geophysics, students compute the tidal acceleration exerted by the Moon and the Sun on the surface of the Earth and calculate the Roche limit for the Earth.

Creep mechanisms

In this practical, adapted from Lowrie and Fichtner (2020) Fundamentals of Geophysics, students investigate the relative importance of dislocation creep and diffusion creep, in relation to pressure, temperature and grain size.

Lithospheric strength

Using the TmScL spreadsheet (Jiménez-Díaz et al., 2012), students investigate the sensitivity of lithospheric strength envelopes to changing parameters that define the thermal, structural and compositional models.

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