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.org/MS-maps/map-pages-worldmap/images-continental/1-continental-pangea-drift.gif
Emerging Evidence for Plate Tectonics
• Mapping the ocean floors using echosounding (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.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