This document discusses different types of plate boundaries and plate tectonics. It describes divergent plate boundaries where new crust is formed, such as at the mid-Atlantic Ridge. Convergent boundaries where plates collide are discussed, like the subduction of the Nazca Plate under South America forming the Andes Mountains. Transform boundaries where plates slide past each other are also mentioned. Various examples are provided of different plate interaction types around the world.

1. Mid-Oceanic Ridges & Sea
Floor Spreading

2. TYPES OF PLATE MOVEMENT
• The ways that plates interact depend on
their relative motion and whether oceanic
or continental crust is at the edge of the
lithospheric plate.
• Plates move away from, toward, or slide
past each other.
• Geologists call these divergent,
convergent, and transform plate
boundaries.

3. DIVERGENT PLATE BOUNDARY
• At a divergent plate
boundary lithospheric
plates move away from
each other.
• The mid-Atlantic Ridge, a
topographically high area
near the middle of the
Atlantic Ocean, is an
example of a divergent
plate boundary.
• New crustal material

5. Anatomy of a Mid-Ocean
Ridge

6. Topography and symmetry of the
ocean floor

7. ANDES
• The Andes Mountain Range spans the entire
length of South America, along the western
coast. This close-up shows that coast, which
represents the western terrestrial edge of
the South American Plate. The leading edge
of the Nazca Plate is subducting below the
South American Plate at a plate boundary
known as a subduction zone. During this
subduction some Nazca crust is scraped off
along base of the Andes, adding height to
the entire range.
• The East Pacific Rise [the ridge to the left] is
part of the global network of mid-ocean
ridges that girdle the planet. As the sea-floor
spreads on either side of this ridge, the
Nazca Plate moves easterly while the
Pacific Plate moves westerly. The
Galapagos Islands, off the northwestern
coast of South America, are the result of a
"Hot Spot" that exists over a mid-ocean
ridge.

9. Divergent: Atlantic Ridge
LAVA FOUNTAINS
KRAFLA VOLCANO
ICELAND

10. Sea-floor spreading
• Mid-ocean ridges long recognized, but
magnetic structure only known since
WWII (anti-submarine technology)
• Symmetric distribution of magnetic
stripes and age of ocean crust was the
key clue
• Demonstrated youth of ocean basins
and continual formation of crust
• Mechanisms related to mantle
convection

11. Fig. Story 2.11

12. The
Geomagnetic
Reversal Time
Scale-Do
Compass and
Magnet
Experiment

13. Magnetic
Stripes in
the
FAMOUS
Area

16. Direct measurement of relative
plate motions

17. Plate Motion Summary

18. Transform boundaries—oceanic plates

19. Continental-continental Collision
Figure 12.16

20. HIMALAYAS

22. Oceanic-Continental Collision

23. RING OF FIRE
OCEANIC-CONTINENTAL COLLISONS SUSTAIN MOST
VOLCANIC ACTIVITY AROUND THE PACIFIC OCEAN

36. Hot spots
• “Plumes” of deep mantle material rising
from the core-mantle boundary
• Cause intense volcanism (Hawaii,
Yellowstone) unrelated to plate boundaries
• Hot spots are fixed in space relative to one
another; plates move across them (e.g.,
Pacific plate). Or are they?

37. HOTSPOTS