Physical Geology Lecture - Plate boundaries and associated geologic activity.

Classification of plate boundary types (bit of review plus expansion):

Map summarizing some of the major plates and plate boundaries. You might practice locating examples of the different types of plate boundaries mentioned above. Image source: http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_world.html

In-class exercise: Develop a classification structure from the intersection of two different sets of classes similar in form to what we explored in class for plate boundaries, but for some other phenomena. The classification can cover any realm, but naturally one that is of interest to you (perhaps related to your career interests) will work best.

Now on to some details.

Subduction-arc complexes - recycling oceanic crust:

UNO students studying Fransiscan melange along the northern coast of California (near the city of Crescent). Note the lack of continuity of layers and features due to the severe deformation this rocks suffered when they were part of a subduction accretionary zone.

Schematic diagram of subduction and spreading ridge off the the coast of Oregon and Washington. Image source - USGS, http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_juan_de_fuca_subduction.html

Mountain building - collisional processes and complexes:

Folded and faulted Mesozoic strata in Spitsbergen, Norway, exposed in a glacial valley wall - simple visual evidence of local crustal shortening.

In this cliff side in the French Alps one can see the tilted sedimentary layers once in the marine realm (e.g. limestones), and a close look shows a recumbent fold in the very middle, the details of which can be seen in the photo below. The Alps formed through a complicated history of small plates and terranes moving northward into Europe as a larger ocean closed to form the present day Mediterranean. The Alps where were some of the earliest studies into tectonics occurred, and this mountain side is an example of why.

This is a more detailed view of the core of the large fold above, displaying what might be considered rather extravagant folding. Folding such as this is one of the major mechanisms of crustal thickening seen in mountain belts.

Transcurrent tectonics:

Supercontinents:

Diagram from USGS Dynamic Earth site showing a simplified reconstruction of continental configurations through time. Site source: http://pubs.usgs.gov/gip/dynamic/dynamic.html .

Hot spots and mantle convection:

 

Map from NOAA showing the linear chain of volcanic islands and seamounts with Hawaii at the end. Source: http://coris.noaa.gov/about/eco_essays/nwhi/archipelago.html

Image from USGS Dynamic Earth site of major hot spots in the world. Notice the proliferation of hot spots in Africa.

Link to course material for Plate Tectonics course.

USGS Dynamic Earth - description of the Plate Tectonic paradigm.


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