1. Harry Hess

2. Recall:
 Scientists know Earth’s interior is made
mostly of layers of _______________.
 Some layers, like the center part, called the
______are hard and______.
 Other layers are not. The layer next to the
center, called the_________, is _______.
Both parts of the core are made
of___________.
inner core; liquid ; rock
iron and nickel; outer core;
solid

3. Recall:
 The largest layer inside Earth is called the
_____. It’s neither completely solid nor
completely liquid, but_____. It’s
extremely______.
 Earth’s outermost layer is the______ . This
layer is about 5 km thick under the_______
and up to 35 km thick under the______.
 On top of the outer layer is the weathered
rock called______.
continents ; mantle; plastic like
crust; oceans; soil; hot

4. Despite the evidences
presented by Wegener, WHY
was his idea that the
continents were once joined
together was not accepted by
the scientific society?
This made scientists conduct
further studies in search for the
answer.

5. 1950s and 1960s- new
techniques and modern
gadgets
sonars and submersibles
scientists had a clearer view of
the ocean floors
discovered underwater
features deep within the ocean

6. a system of ridges or
mountains in the seafloor
similar to those found in the
continents (mid-ocean ridges)
Mid-Atlantic Ridge: an undersea
mountain chain in the Atlantic
Ocean
a gigantic cleft about 32-48 km
long and 1.6 km deep

7. Mid-Atlantic
Ridge

8. Activity 5: Split and Separate!
Simulate and describe the
seafloor spreading process.
• Realize the importance of the
seafloor spreading process
relative to the Continental Drift
Theory.

9. Paper
Folder

11. Answer:
Q22-27

12. Describe and explain
each
diagram/illustration.

13. Harry Hess

15. Magnetometer

18. Sea Floor Spreading
 early 1960’s- Harry Hess, together with
Robert Dietz
 Seafloor Spreading Theory
 hot, less dense material from below the earth’s
crust rises towards the surface at the mid-ocean
ridge
 material flows sideways carrying the seafloor
away from the ridge, and creates a crack in the
crust
 magma flows out of the crack, cools down and
becomes the new seafloor

21. Sea Floor Spreading
 allowed the creation of new bodies of water
 the Red Sea -African plate and the
Arabian plate diverged
 pulling Australia, South America, and
Antarctica away from each other in the
East Pacific Rise
 The East Pacific Rise -the most active
sites of seafloor spreading, more than
14 cm/yr

22. SFS
 rate of formation of a new seafloor is not always
as fast as the destruction of the old seafloor at
the subduction zone
 explains why the Pacific Ocean is getting
smaller and why the Atlantic Ocean is getting
wider
 If subduction is faster than seafloor spreading,
the ocean shrinks
 When the seafloor spreading is greater than the
subduction, then the ocean gets wider

24. The SFS contradicts a part of the
CDT
CDT- continents moved through
unmoving oceans and that larger,
sturdier continents broke through the
oceanic crust
Whereas, the seafloor spreading
shows that the ocean is the actual
site of tectonic activity

25. Findings that support Seafloor Spreading Theory:
Rocks are younger at the mid-ocean
ridge.
Rocks far from the mid-ocean ridge
are older.
Sediments are thinner at the ridge.
Rocks at the ocean floor are younger
than those at the continents.

26. Bring the ff:
 Pencil
 Ruler

27. Activity 6: How fast does it go!
Objectives:
• Analyze a magnetic polarity
map.
• Use legends and scales of the
map properly.
• Calculate the rate of seafloor
spreading using magnetic clues.

28. VISIT, EXPLORE, ANSWER
 http://www.montereyinstitute.org/noaa/lesson02/l
2la1.htm
 http://earthguide.ucsd.edu/eoc/teachers/t_tectonic
s/p_seafloorspreading.html

29. Answer:
 Q28-29

30. Magnetic Reversal
magnetic ‘flip’ of the Earth
the North Pole is transformed into
a South Pole and the South Pole
becomes the North Pole
due to the change in the
direction of flow in the outer
core

31. Magnetic Reversal
 explained through the magnetic patterns
in magnetic rocks, especially those found
in the ocean floor
 When lava solidifies, iron bearing
minerals crystallize
 the minerals behave like tiny compasses
and align with the Earth’s magnetic
field so when magnetic reversal occurs,
there is also a change in the polarity of
the rocks

32. Describe and explain each
diagram/illustration.

40. Age of Oceanic Crust

41. Divergent: Iceland

42.  Over the last 10 million years, there has
been an average of 4 to 5 reversals per
million years.
 New rocks are added to the ocean floor
at the ridge with approximately equal
amounts on both sides of the oceanic
ridge.
 The stripes on both sides are of equal
size and polarity which seemed to be
mirror images across the ocean ridge.

43. What does this
indicate?
It indicates that
indeed, the seafloor
is spreading.

44. NET RESULTS
 Spreading rates at transform faults
 Pacific plate moves NW at 8 cm/yr
 N American plate moves W at 2 cm/yr
 Indian plate moves NE at 12 cm/yr
 Pacific Ocean is shrinking and Atlantic
is growing
 Atlantic opened about 200 MY ago so there
should be no rocks older than this in the
Atlantic

45. Most recent episode
of
Seafloor spreading:
Pangaea first broke
into 2 pieces
Sea opens between N
and S continents and
Between Africa and
Antarctica
India moves North

46. S Atlantic opens
Antarctica moving S
India moving N
Australia separates
and moves N

47. 50 MY in the future:
1. Africa will move N and
close Mediterranean Sea
2. E Africa will detach (Red
Sea rift zone) and move to
India
3. Atlantic Ocean will grow
and Pacific will shrink as it
is swallowed into Aleutian
trench.
4. W California will travel
NW with the Pacific Plate (LA
will be swallowed into the
Aleutian trench in 60 MY).

48. Bring the ff: (by group)
dropper
food color
3-5 small / light wood
blocks
(or sponge cut into thin and
small blocks)