1st quarter grade 10 science - seafloor spreading theory and its evidences good for 2 hours.I hope the videos included will play

2. At the end of the lesson,
you should be able to:
 Describe how seafloor spreading
happens
 • Explain how drill samples proved that
seafloor is spreading.

7. Sea-Floor Spreading

8. https://www.youtube.com/watch?v=ZzvDlP6xd9o

9. Guide Questions
1. What is seafloor spreading?
2. What is formed at the mid-ocean
ridges?
3. Where is the oceanic crust
destroyed?
4. How many inches does the seafloor
spreads every year?

11. Sonar - a device
that bounces
sound waves off
under-water
objects and then
records the
echoes of these
sound waves. The
time it takes for
the echo to
arrive indicates
the distance to
the object.

13. SEAFLOOR SPREADING
 the process that continually adds new
material to the ocean floor while
pushing older rocks away from the
ridge
 New oceanic crust is created at the
ridges and recycled at the trenches
 Seafloor spreading is not consistent at all mid-ocean ridges.
It spreads 2-5 centimeters (.8-2 inches) every year

14. As magma bubbles up at sites of seafloor spreading, it is cooled by frigid
seawater and becomes Earth's newest oceanic crust. Most of this new
igneous rock is basalt, like this pillow lava that bubbled up at the East
Pacific Rise near the Galapagos Islands.

15. Slow spreading centers have steep cliffs
and plunging ocean trenches. This rocky
outcrop is part of the slow-spreading
Mid-Atlantic Ridge, where it juts above
sea level on the island of Iceland. To the
left is the eastern edge of the North
American continent. On the right is the
western edge of Eurasia. (Fast spreading
centers, such as the East Pacific Rise,
have more gentle slopes and lack deep
trenches.)

16. Sea-Floor Spreading
1. Evidence from drill samples
The samples obtained from the
seafloor drill reveals that the rocks
away from the mid-oceanic ridge were
relatively older than the rocks near to
it.

18. Seafloor spreading helps create mid-ocean ridges, giant underwater mountain ranges that
develop where tectonic activity is driving plates apart from each other. This lovely map highlights
where tectonic plates are separating at mid-ocean ridges.

19.  Rocks are younger at the mid-ocean
ridge
 Rocks farther 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)

20. Atlantic ocean
getting bigger.
Pacific ocean
getting smaller.

21. The oldest rocks found on the ocean
floor are about 160 million years old. The
Earth is about 4.6 billion years old. Why
are there not any rocks older than 160
million years on the seafloor?
What happened to the older rocks?”

22. Draw a diagram that
illustrates seafloor
spreading. Use arrows to
indicate the direction of
plate motion and label the
“youngest” and “oldest”
crust.

23. END OF part 1

24. Sea-Floor Spreading
2. Evidence
from Magnetic
Stripes – Rocks
that make up
the ocean floor
lie in a pattern
of magnetized
stripes which
hold a record of
the reversals in
Earth’s magnetic
field

26. https://www.youtube.com/watch?v=WhiF6IqGACo

29. Sea-Floor Spreading

30. Sea-Floor Spreading

32. QUIZ

33. 4. At mid-ocean ridges, new
____________________________ crust is
created.
A) convergent
B) transform
C) oceanic
D) volcanic
E) continental

34. 5.As the ocean seafloor spreads, the newly
formed floor will adapt a specific magnetic
signature according to the Earth's magnetic
pole at that time. As years pass, lateral
segments of seafloor will thus share the
same _____________________ signature
on either side of the mid-oceanic ridge.
 A) volcanic
B) divergent
C) zubductive
D) magnetic
E) convergent

35. 6.In seafloor spreading, the further the ocean
floor is away from the mid-ocean ridge, the
_____________________ that floor will be.
A) newer
B) rockier
C) prettier
D) younger
E) older

36. 7.Which is NOT involved in the
process of sea floor spreading?
a.Mid-ocean ridges
b.Magma
c.The newest rock is at the center
of the mid-ocean ridges
d.It tends to happen near the edges of
continents

37. 8.A ____ is a sensitive device used to
detect magnetic fields on the seafloor.
a.magnetometer
b.geologist's compass
c. SONAR
d.seismometer

38. 9.The magnetic pattern of ocean-floor
rocks on one side of an ocean ridge is
____.
a. a mirror image of that of the other side
b. younger than on the other side
c. much different from the magnetic
pattern found in rocks on land
d. at right angles to the ocean ridge

39. 10.While studying the ocean floor,
scientists found ____ bands of magnetism.
a.plastic
b.no
c.sediment
d.alternating

40. Answers
1. B
2.C
3.A
4.C
5.D
6.E
7.D
8.A
9.A
10.D