Overview of Plate Tectonics Processes But NO PROOF!!!

To sustain such topography the earth must be dynamic

Earth’s primary Layered structure

What is the “shallow” structure? Shallow = ~ 200 km Note the names of the layers and thicknesses. Not labelled: Inner core begins at ~ 5,150 km depth

CRUST and UPPER MANTLE

Note: image not extended to full lithosphere depth

Typical Numbers for “crustal thickness” Continental: Average ~ 35 km Continental: Range: 20 – 75 km Oceanic: Average ~ 7 km Oceanic: Range ~ 5 – 10 km Lithosphere: (fill in yourself!) Asthenosphere: (fill in yourself!)

Cross section of the earth

EARTH’S DENSITY AS A FUNCTION OF DEPTH APPROXIMATE COMPOSITION OF MAJOR LAYERS

DENSITY vs DEPTH

Composition in the major layers of the Earth

Generating New (Oceanic) Crust Seafloor Spreading (Divergent Plate Boundary)

A Research Article (Just to point out that EAR is an active research area) History of the development of the East African Rift System: A series of interpreted maps through time https://www.sciencedirect.com/science/article/pii/S1464343X14003240

What happens to all this new oceanic crust? Subduction Zones (Convergent Boundary)

Generate continental Crust (subduction zone)

Generate Oceanic Crust (subduction zone)

What happens when trailing continental crust collides? (convergent boundary)

http://emvc.geol.ucsb.edu/1_DownloadPage/Download_Page.html India/Asia: http://emvc.geol.ucsb.edu/2_infopgs/IP1GTect/dContCollision.html

What’s happening on the ocean floor during all this?!?! Transform Plate Boundaries (and Divergent, again)

Marie Tharp produced the first maps of mid-oceanic ridge system and the axial valleys between the ridges

Note the three types of plate boundaries and types of locations.

How did we get to our present configuration of oceanic and continental crust?

Plate Tectonics Is an excellent unifying model of earth dynamics as a whole Context for understanding earth processes Create testable hypotheses, predictions “Exceptions” exist

No “proof” has been provided for any of the ideas presented above Evidence for these processes will be noted and discussed as the class goes on. Processes have been stated to give context for our study of geologic processes No “proof” has been provided for any of the ideas presented above IMPORTANT CLASS THEME

Plate Tectonics Is Still Not Fully Understood Simplest possible question: When did Plate Tectonics begin?

Advice When reading and thinking about geology, have scratch paper handy – sketching processes will really help you learn and internalize the ideas. Often, an exam/quiz question I write will say Use an annotated sketch to explain …