Types of Plate Boundaries Created by Dr. Michael J. Passow

Wegener’s “Continental Drift” Hypothesis: All continents once joined together as supercontinent PANGAEA. Over millions of years, continents split and moved to present positions (next slide) Evidence: matching coastlines, fossils, rocks, ancient climates Weakness: no explanation of continents could move (“driving mechanism”) Result: rejected for decades

http://www. mapsharing http://www.mapsharing.org/MS-maps/map-pages-worldmap/images-continental/1-continental-pangea-drift.gif

Emerging Evidence for Plate Tectonics Mapping the ocean floors using echo-sounding (sonar) records Paleomagnetism patterns in ocean basalt Earthquake epicenter patterns Volcano locations Hot Spots (ex., Hawaii and the Emperor Seamounts) Ocean drilling

Continental Drift to Plate Tectonics By the late 1960s, the many lines of geoscience data obtained through developing technologies all provided evidence that: 1) surface plates existed and 2) they are moving very slowly in three basic patterns

Divergent/Convergent/Transform plate boundaries http://www.uwsp.edu/gEo/faculty/ozsvath/images/plate_boundaries.htm

Divergent Boundaries (spreading centers) http://www.geology110.com/files/lecshare1/html/web_data/file50.htm

Continental Rift Valleys Perhaps the most famous example is the East African Rift Valley. Eventually, a new ocean may form here. (2- 3 million years ago, humans first evolved here.) http://education.usgs.gov/common/lessons/act5.html

Convergent Boundaries (subduction zones) http://www.geology110.com/files/lecshare1/html/web_data/file51.htm

Ocean-continent convergent boundaries http://sio.ucsd.edu/volcano/about/images/recycle.gif

Most of the Pacific Ring of Fire consists of ocean-continent boundaries http://www.geocaching.com/seek/cache_details.aspx?guid=e83ed03c-349a-4ac5-a91c-a467cb9f92f2

Ocean-ocean convergent boundary Japan http://blue.utb.edu/paullgj/physci1417/Lectures/Plate_Tectonics.html

Continental-continental convergent boundary The Himalayas are one of the best examples of this type of boundary. http://www.utexas.edu/tmm/npl/mineralogy/mineral_genesis/index.html

Transform Fault Boundaries http://www.geology110.com/files/lecshare1/html/web_data/file52.htm

http://homepage. ufp. pt/biblioteca/GlossarySaltTectonics/Pages/PageT http://homepage.ufp.pt/biblioteca/GlossarySaltTectonics/Pages/PageT.html

Continental transform fault: San Andreas system Most transform faults exist in the ocean floor One important example on a continent is the San Andrea system http://geology.com/articles/san-andreas-fault.shtml

Putting It All Together http://www.geology110.com/files/lecshare1/html/web_data/file54.htm

Causes (Driving Mechanisms) for Plate Tectonics Convection Slab-Pull and Ridge-Push Mantle “plumes” “Whole Mantle” and “Mantle-Core” models