Seafloor Spreading Lab

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Transcript Seafloor Spreading Lab

Seafloor Spreading Lab
1. What is happening at Slit B? What
feature occurs at the corresponding
location on the seafloor?
• Magma is being forced upward creating new
ocean floor. The feature that occurs at slit b
stands for the central valley of the mid-ocean
ridge.
2. What is happening at Slit A and C?
What features occur at corresponding
locations on the seafloor?
• The oldest ocean floor collides with the
continental crust. The more dense oceanic
crust sinks back into the mantle. The feature
that occurs at slit A and C is a subduction
zone or deep ocean trench.
3. If you were to sample and date the
rocks along the colored strip starting
at Slit B and moving toward Slit A,
what change would you see in the age
of the rocks?
• If you were to sample and date the rocks
along the colored strip starting at slit B and
moving toward slit A, the rocks would be
getting older.
4. If you were to sample and date the
rocks along the colored strip starting
at Slit C and moving toward Slit B,
what change would you see in the age
of the rocks?
• If you were to sample and date the rocks
along the colored strip starting at slit C and
moving toward slit B , the rocks would be
getting younger.
5. In this model, what do the strips
represent? What do the colors
represent?
• The strips represent the ocean floor. The
colors represent the ages of the rocks.
6. How does the ocean floor as shown
by the part of a strip close to the
center slit (Slit B) differ from the ocean
floor as shown by the part near a side
slit (Slit A or C)?
• The ocean floor as shown by the strip near
the center slit is younger, hotter and less
dense than the ocean floor farther away. As
the floor moves away from the ridge, it cools
and becomes denser.
7. How does this difference affect the
depth of the ocean?
• Since the ocean floor gets cooler and more
dense as the material moves toward the side
slits, the depth of the ocean floor increases.
8. Why is it important that your model
have an identical pattern on both
sides of the center slit?
• It is important to have identical patterns of
stripes on both sides of the center slit
because this represents that the ocean floor
is expanding. Rock found at the same
distance on either side of the mid-ocean
ridge would be the same age, have the same
composition, and have matching magnetic
characteristics. The identical pattern
provides evidence for seafloor spreading.
9. What causes the plates to be pulled
apart?
• As new ocean floor forms at the mid-ocean
ridge, older ocean floor moves away from the
ridge and this causes the plates to move
away from one another.
10. Use your own words to describe
the process of seafloor spreading.
• At the mid-ocean ridge, molten material rises
from the mantle and erupts. The molten
material then spreads out, pushing older rock
to both sides of the ridge. Over tens of
millions of years, the process continues until
the oldest ocean floor collides with the
continental crust. The more dense oceanic
crust subducts (sinks) back into the mantle at
a deep-ocean trench.