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We will discuss We will discuss solid-state solid-state deformationdeformation

Plate Tectonic Theory

Controls on the location and patterns of deformation

What drives plate motion?

Ridge push - driven by elevation of mid-ocean ridge

Slab pull - as ocean crust grows older and colder, it becomes progressively denser and sinks

Basal traction - crust pulled from below by convecting mantle

Plate tectonic motions over time At times in the past, plates have come together

to form large ‘supercontinents’ Land mass has at times been localized at the

equator, at times stretched to the poles, sometimes concentrated in one hemisphere

Plate motions can be described by rotations around poles

Rotations produce convergent, divergent, and transcurrent motions at boundaries

Observing a structure What does it look like? Where is it found on the Earth, and what (if any)

are its associations with other structures or specific rock types?

What is its 3D geometry? What patterns do structures in this category or

tectonic environment form? What do 3D geometry and patterns tell us about

material controls (heterogeneity, anisotropy, relative competence) on formation?

Patterns of structures reflect the character of the tectonic boundary

A complete map of active structures in this area would include folds

What about depth?

Character of structures in a given area depends on:

Tectonic setting Rock type Temperature, pressure, fluid content Strain rate