1. Tectonic Plate Boundaries

2. Plate Boundaries - where the edge of two plates meet.
3 Plate Boundaries and 1 other
1. Divergent - occurs where
plates move apart (mostly
in oceans)
2. Convergent - occurs where
plates push together
3. Transform - occurs where plates
scrape past each other
4. Hot Spots

3. Occurs where two plates split apart
Divergent Boundaries
Occurs where two plates split apart

4. How, you ask? Divergent boundaries form when hot material rises
Heat causes crust to buldge upward
Crust cracks and a rift valley forms

5. Magma rises through cracked, thinned crust, forming volcanoes
Continued…
Magma rises through cracked, thinned crust, forming volcanoes
If rift valley continues widening it will sink below sea level and water from near by oceans will fill in
ex.) Red Sea

6. http://www. lincoln. smmusd

7. Divergent Boundaries Mid-Ocean Ridges and Rift Valleys
A. Mid-Ocean Ridges
Longest chain of mountains
Most contain a rift valley along their center
EX.) Mid-Atlantic Ridge - reaches from Iceland to Antarctica in Atlantic Ocean

8. Rift Valley Gap at center of Mid-ocean ridge
Molten material rises from asthenosphere, water cools the rock until it becomes solid

9. http://www. harcourtschool. com/scienceglossary/images/gr6/midocean_r6

10. Convergent Boundaries
Occurs where plates push together
Crust is either folded or destroyed

11. Subduction Zone When one plate sinks below another
crust melts in the asthenosphere and is destroyed

13. Oceanic Crust – crust that is thin but very dense (tightly packed)
Continental Crust – crust that is thick but less dense (not tightly packed)

14. A. Continental-Continental Collision
Occurs where two continental plates
push together
Neither plate sinks because both
plates have the same density
Plate edges will crumple and fold,
often forming mountains
ex.) Himalayas (still forming today)

16. B. Oceanic-Oceanic Subduction
Occurs where one plate with oceanic
crust sinks, or subducts, under another plate with oceanic crust
Older plate sinks because it is colder
and more dense
When it reaches the asthenosphere it
melts in the intense heat

17. 2 features form at oceanic-oceanic subductions
Deep-Ocean Trenches
deep canyons that form in ocean floor (most found in Pacific Ocean)
EX.) Pacific Plate under Philippine Plate, deepest spot is 11,000 meters into sea floor
Island Arcs
chains of volcanic islands that form on the top of plates
Form parallel to deep-ocean trenches
EX.) Japan, Philippine Islands

19. C. Oceanic-Continental Subduction
Occurs when ocean crust sinks
under continental crust
Oceanic sinks because it is
colder and denser than
continental crust

20. 2 features form at oceanic-continental subductions
Deep-Ocean Trenches
Ex.) Pacific Plate under North American Plate (underwater earthquakes)
2. Coastal Mountains
continental crust buckles to form a range of mountains
Mts. Parallel to deep-ocean trenches (some form volcanoes)
Ex.) Cascade Mts. In Oregon and Washington (Mt. St. Helen’s)

23. Occurs where two plates move past each other in opposite directions
Transform Boundaries
Occurs where two plates move past each other in opposite directions

24. As plates move, their edges scrape and grind against each other
Occurs mostly near mid-ocean
ridges
EX.) San Andreas Fault
At its present rate, LA will be a suburb of San Fran in 10 million years.

26. Hot Spots Can be used to track plate movement
Hot spots - heated rock rises in plumes, or thin columns, from the mantle
Volcanoes often develop above plumes
Hot spot stays in one place as tectonic plate moves above it
EX.) Hawaiian Islands