Transcript sea-floor spreading

September 25, 2013
Agenda
1. Roll
2. PowerPoint “Restless
Continents”
Subject Area: Restless Continents
EQ: How does the fit of the continents provide
evidence for plate tectonics?
Questions:
1. Why was Wegner’s theory of continental
drift not accepted at first?
2. How does sea floor spreading provides a
way to explain how continents move?
3. How does new oceanic crust forms at midoceanic ridges?
4. How does magnetic reversals provide
evidence for sea-floor spreading?
Restless Continents
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Wegener’s Theory of Continental Drift
The Breakup of Pangaea
Sea-Floor Spreading
Magnetic Reversal
Untold tragedies of Continental Drift.
Restless Continents
If you look at the continents they would fit
together. It is possible that the continents
were actually together sometime in the
past.
Wegner’s Theory of Continental
Drift
In the Early 1900’s Alfred
Wegner wrote about the
theory of continental drift.
Continental Drift is the
theory that continents can
drift apart from one another
and have done so in the
past. Some fossils were
found on both sides of an
ocean, there is no way the
ancient animal
could
have
Partner
Question:
crossed theWhat
ocean.
is the theory of Continental Drift?
Wegner’s Theory of Continental
Drift
Continental drift also explained the evidence left by
glaciers. The glaciers cut grooves that can be
matched in their original arrangement. The
Glacial grooves fit together.
The Breakup of Pangaea
Wegener thought the separate continents of
today were once joined in a single landmass.
This landmass he called Pangaea. Pangaea
is the Greek word for “all earth” where all the
continents were once joined together.
Partner Question:
What does Pangaea mean?
Sea-Floor Spreading
Wegner could not explain how the continents
moved. Later scientists discovered Mid-oceanic
ridges. This is where sea-floor spreading takes
place. Sea-floor spreading is the process by
which new oceanic lithosphere is created as
older materials are pulled away.
Partner Question:
What is Sea-Floor spreading?
Magnetic Reversals
In Earth’s history, the north and south magnetic
poles have changed places many times. When
the magnetic poles change it is called magnetic
reversal. Minerals record the magnetic signal in
stone. Then it moves with the moving material
across the ocean floor. This is just more proof
that sea-floor spreading does occur.
Partner Question:
What is magnetic reversal?
Intro to Continental Drift
What did I know?
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2.
3.
What did I learn?
1.
2.
3.
What do I want to know
more about?
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3.
Pangaea Puzzle
You are only coloring today.
Do not cut any out today.
We will do that tomorrow!!!
Class work
Workbook Chapter 6 section 2 on
pages 40 – 42.