Lecture Notes from January 6:

Much of the first hour was spent discussing logistics and course format.  Following this we discussed the morphology of ridges and examined some maps.
 

Motivating questions:

• How does the morphology of ridges vary as a function of spreading rate?
• How do magmatic and tectonic processes vary as a function of spreading rate?
• What is the length scale of along-axis segmenation of ridges as a function of spreading rate?

Given answeres to the above, we can then compare the dimensions and physical characteristics of the Oman ophiolite to those expected for oceanic crust formed at different spreading rates.
 

• On the basis of structural evidence, was the Oman ophiolite formed at a fast or slow spreading ridge?

We will learn that beyond the structural evidence, there is petrologic arguments that indicate at what type of ridge the Oman ophiolite was formed.

Outline material covered or to be read about:

• Morphology of fast- and slow-spreading ridges:
• Ridges in cross-section
• Ridges in map view
• Tectonic boundaries
• Transforms
• Overlapping spreading centers
• Non-transform offsets
• Gravity along ridges
• Mantle Bouguer anomalies:  A proxy for crustal thickness
• MBA along slow spreading ridges
• MBA along fast spreading ridges

 

In recent years there have been several review papers related to mid-ocean ridges.  These are not required reading, however, I suggest scanning the various papers (particularly their figures) to get an idea of variability in ridge crest structure.

*Forsyth, D. W., Geophysical constraints on mantle flow and melt geneartation benat mid-ocean ridges. In Mantle Flow, Melt Generation and Lithospheric Deformation at Mid-ocean Ridges, Geophys. Mongogr., Washington, DC: AGU

Macdonald, K.C. and others, A new view of the mid-ocean ridge from the
    behaviour of ridge-axis discontinuities, Nature, 335, 217-225, 1988.

*Solomon, S.C and Toomey, D.R., The structure of mid-ocean ridges,
    Annu. Rev. Earth Planet. Sci., 20, 329-364, 1992.

*Indicates that a single copy of the paper or the book can be found in the foyer of Cascade 105.