• Outline: Plate Boundaries & Convection

  • FileName: Plate_Tectonics.pdf [read-online]
    • Abstract: Plate Boundaries. • Hot Spots. • Convection & plate tectonics. 2. 1. All but one of these ... Transform Fault (Plate Boundary) 7. 37. 38. 39. lip fault: At a spreading mid-oceanic ridge, ...

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1. All but one of these pieces of evidence
Outline: Plate Boundaries & Convection were used by Alfred Wegener to support his
hypothesis of Continental Drift. Find the one:
• Review a. the continent shapes fit together
b. fossils of identical freshwater reptiles found
• Plate Boundaries on opposite sides of the Atlantic Ocean
• Hot Spots c. matching rock types where continent
shapes fit together
• Convection & plate tectonics d. the age of rocks on the sea floor
1 2
3. The distribution of glacial landforms on several
continents between the equator and the south pole
2. Sea-floor spreading was an idea that could provide a suggested to Wegener that:
mechanism for Continental Drift. Which of the following a. the climate was once much colder in the tropics
discoveries were used as evidence for the concept? b. continents were adjacent to each other in the past
a. the mid-Atlantic oceanic ridge with a central rift within it
c. these continents were once further south
b. the magnetic reversals in the rocks on either side of the
mid-oceanic ridge d. answers b and c
c. the age of rocks increases away from the mid-oceanic e. answers a, b, and c
d. matching fossils on either side of the Atlantic Ocean
e. answers a through c
f. answers a through d
3 4
What kind of plate boundary is this?
Identify the two tectonic plates in this figure. Which way is the land on each side moving?
Identify the oceanic lithosphere in this figure. What is the valley called?
5 6
Along spreading ridges or rifts:
• shallow
See p. 50 for
good diagrams • along axis of
& explanations of
sea-floor spreading.
7 8
Two examples
Rio Grande Rift East African Rift
San Luis Valley, CO - Red Sea
•Pull apart zones
•Linear lakes
(early oceans)
San Luis Valley
9 10
The North American continent sits
on the same plate that the western
half of the Atlantic Ocean sits on.
A passive margin is the transition between oceanic and continental
crust which is not an active plate margin. 11 12
There are 3 types of A. Ocean to Continent
convergent Boundaries
• oceanic plate subducts under a
continental plate
13 14
Increasing density
Why is it so deep here? The oceanic crust is more dense here,
15 16
and is being dragged downward
B. Ocean to Ocean
Subduction of one oceanic plate under
another oceanic plate
Example: Cascade Mountain Range 17 18
Earthquakes and volcanoes develop along
Deeper earthquakes are stronger.
the convergent plate boundary.
19 20
What kind of plate boundary is this?
C. Continent to Continent
Collision of two continental plates
Mt. Fuji, Japan
•Line of volcanic islands in ocean
•Parallel to trench
•100-400 km from trench
•Steeper angle of subduction deeper quakes = stronger
21 22
Look at for a location where there are
mountains within the interior of a continent
where a continent – continent collision may
have occurred..
23 Example: Cascade Mountain Range 24
Himalayas =
Collision of
Indian and
Eurasian plates
Deep and shallow
25 26
What is going on in this sequence?
Where is there an active
margin and a passive
• Mariana Trench: ~11,000 m deep
• compare to Mt. Everest: 8,854 m high
27 28
In a strike s fault, the fault plane or surface is
- lip
nearly vertical.
Transform Boundaries
29 30
5 cm/yr
Off-set Stream Carrizo Plain, CA 31
Displacement of creek, San Andreas Fault CA 32
LA in 10
million years
33 34
Transform Fault (Plate Boundary)
Pacific Plate
35 36
37 38
lip fault:
At a spreading mid-oceanic ridge,
the land is moving away from the
ridge on both sides.
Sketch a fault like this in your
book and add arrows to show the A A
direction of plate motion on each
side of the ridge.
Based on your understanding of
plate motion, choose the direction B B
of movement for land at point A
and point B. 1. A moves right, B moves left
2. A moves left, B moves right
1. A moves right, B moves left 3. A and B move left
2. A moves left, B moves right 4. A and B move right
3. A and B move left
4. A and B move right Why? Because sea-floor is
spreading at mid-oceanic ridges…
39 40
Transform Fault (Plate Boundary)
41 42
There are 3 types of plate tectonic environments:
Extensional, compressional, and transform
(match them up with the plate boundary types).
43 44
• Plate moves over “hotspot,” and magma
upwells, creating volcanoes & underwater
mountains. 46
Continental crust also moves over hotspots
creating volcanoes, as at Yellowstone Nat.
47 48
c ha
49 50
Quiz question
4. As oceanic crust movers away from spreading zones at
mid-oceanic ridges (towards continents), it becomes:
a. colder, more dense, and the ocean depths increase
b. colder, less dense, and the ocean depths decrease
c. warmer, less dense, and the ocean depths decrease
51 52
5. Draw a convergent plate boundary.

Use: 0.0238