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Published on Nov 19, 2015
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PRESENTATION OUTLINE
CHARACTERISTICS OF PLATE BOUNDARIES
DIVERGENT BOUNDARIES
- Where the sea floor is spreading apart
- Ridges form at spreading centers and volcanoes form
- And small earth quakes happen
LOCATIONS
- Mid atlantic ridge
- East pacific rise
- The east African great rift valley
CONVERGENT BOUNDARIES
WHEN PLATES MOVE TOWARD EACH OTHER AND ONE GOES UNDER THE OTHER
EXAMPLE
THE MARIANA TRENCH IS CONVERGENT
TRANSFORM FAULTS
WHERE PLATES SLIDE PAST EACH OTHER AND EARTHQUAKES OCCUR
SAN ANDREAS FAULT LINE
TRANSFORM BOUNDARIES
- They mark the locations at which crustal plates move past each other.
- They produce distinct topography & contain potential dangers for human inhabitants.
- 1950s, geophysicists towed sensitive magnetometers just above the ocean floor to detect weak magnetism.
- 1963 geologists realized that the pattern of alternating weak and strong magnetic fields were symmetric.
- The young spreading ridges are almost free of sediment.
Untitled Slide
- The oldest sediment are more than 180 million years old.
- Among the most convincing is the study of paleomagnetism, the orientation of Earth's magnetic field frozen into rock as it solidifies.
SEAFLOOR SPREADING
- The theroy that new ocean crust forms at spreading centers
SUPERPLUME
- Very large mantle plumes
OPHIOLITES
- An assemblage of subducting oceanic lithosphere scraped off onto the edge of a continent
