Ge161-2005 : Introduction
Instructor Jean-Philippe Avouac
TA: Nathan Downey
Outline
During this class you will be exploring the earth dynamics based on a number of physiographic, geological and geophysical observations that you will be making yourself during the labs. The labs will lead you to develop a quantitative description of current plate kinematics as well as over a geological period of time. We will first introduce the formalism used to describe the kinematics of a deforming spherical earth surface. We will next give an overview of the structure of the earth, as it can be inferred from global seismology, gravity and describe processes at plate boundaries. We will introduce basic techniques used to construct plate tectonics models based on geodesy, or on paleomagnetism and magnetostratigraphy. We will also discuss how plate tectonics relates to heat transfer in the earth, and to buoyancy forces.
Organization
We will meet each week 2 times for 3-hours classes (9 to 12 am). During each class we will first debrief the previous lab, introduce some basic concepts and tools for the current lab. During the lab we will be using ArcGIS and Matlab. The work during the labs will be collaborative (not the Homework!). Students are required to complete reading required for each week before the first class of that week.
Homework
They will consist in analyzing lab results, exercises, and readings.
Final report
Each student will have to return a final report due on March 12. The focus will have to be on a specific area and the student will have to discuss how a variety of observations (seismicity, geodetic data, magnetic anomaly, age of sediments on the sea floor, bathymetry…) can be reconciled from plate tectonics. The report must be written as a short research paper (equivalent to 4-6 printed pages at most with typically 4-6 figures). The paper will have to be organized in a standard way (observations, Intrepretation, Modeling, Discussion) and all the data used will have to be referenced. The report will in fact mostly summarize part of the work done during the labs.
Grading
40% : Labs and Homework
30%: Final report
30% : Final exam
Text books
- Cox and Hart (‘C&H’), ‘Plate Tectonic : How it works’
- Fowler (‘F’) ‘The Solid Earth: an introduction to Global Geophysics’
Ge 161-2005: Syllabus
Week 1 (January 3-7):
Organizational meeting and introduction to ArcGIS and Matlab
Start reading for week 2.
Week 2 (January 10-14):
Class content :
Spherical and Cartesian coordinates, Small and Great circles, Projections, Reading: C&H, chapter 3, F, Chapter 5
Lab 1: Physiography of the earth
Data: Topography and Bathymetry; Earthquake catalogues, Actives volcanoes…
Work to be done: Describe the main elements of earth physiography; extract a number of topographic sections across some of the key features and compare with distribution of seismicity and active volcanoes. Select key areas and comment.
Homework (2 hours): Due on January 17.
Return a document (with some figures) summarizing key observations made during the lab.
Week 3 (January 17-21) :
Class content :
Kinematics of deformation on the sphere, types of plate boundaries, Euler Poles
Reading: C&H, chapter 3, F, Chapter 5
Lab 2 : Kinematics of current deformation
Data: Same as lab 1 + GPS measurements from Sella et al [2002].
Work to be done: Analyze relative motions of GPS stations and identify rigid domain and zones of deformation. Determine Euler poles describing the motion of some rigid domains.
NB: by the end of week 3 each student will be asked to pick a region for the focus of his final report, and get his choice approved by the instructors. We will provide each student with the document: Global Tectonic Map of the World (GTAM.pdf) It is important that each student becomes familiar with this map (name of major plates and plate boundaries, rates….).
Week 4 (January 23-January 28):
Class content:
Earthquakes and seismic waves, Focal mechanisms
Reading: C&H, chapter 6; F, chapter 4, section 4.2
Lab 3 : Kinematics at Plate Boundaries and Seismotectonics
Data: same as lab2 + CMT focal mechanism
Work to be done : construct a model of modern plate kinematics for a selection of plates. Compare azimuth of slip vectors and of transform faults, from relative plate motion computed form the set of Euler pole. Discuss the significance of slip vector along various type of plate boundaries.
Week 5 (January 31-February 4):
Class content:
Processes and long term kinematics at plate boundaries, Triple junctions.
Reading: C&H chapter 1&2; F, Chapter 1
- Finite Rotations, composition of rotations.
Reading: C&H, chapter 7.
Lab 4 : From modern to past kinematics, using Hot Spots
Data : Data set of dated hot spots from Clouard and Bonneville, (2001)
Work to be done: Test the relative stability of Hot Spots. Determine the motion of the Pacific plate relative to the Hot Spot reference frame over the last 60 Myr.
Week 6 (February 7-11):
Class content
- Rock magnetism, the earth Magnetic field and plate tectonics
Reading : C&H, chapter 8 and 9
Lab 5 : Determine the history of spreading across a ridge from magnetic anomalies.
Data : Magnetic anomaly from the Indian Ocean.
Work to be done: Model magnetic anomalies using Modmag, interpret ages. Determine spreading rates. Determine the kinematics at the Rodriguez Triple Junction from anomaly 22 to 26.
Week 7 (February 14-18):
Lab 6 : Plate closure circuit
Work to be done: Determine the motion of India relative to Eurasia over the last 100 Myr based on global map of sea floor age.
Week 8 and 9 :
Work on final report
Reading: Heat transfer and thermal structure of the lithosphere, F, chapter 7; Pollack et al, 1993.
Week 10:
March 8: Presentations by the students.
Week 11:
March 12, 11-noon: Discussion, what drives plate tectonics?
Reading: C&H, chapter 10.
Final report due on Monday 12
Final exam (2 hours in class)
End of term: march 17
Text books (*primary reading) :
*Cox, Allan, and R. B. Hart, Plate Tectonics: How It Works. Blackwell Scientific Publications, 1986.
*Fowler, C. M. R., The Solid Earth: An Introduction to Global Geophysics, Cambridge University Press, 1990.
Moores, E. M., ed., Shaping the Earth: Tectonics of Continents and Oceans (Readings from Scientific American), Freeman & Company, 1990.
Turcotte, D. L., and G. Schubert. Geodynamics, 2nd edition. Cambridge University Press, 2002.
A number of complementary articles are available on JPA ftp site, together with some material for the class.