Transcript Chap7Sect2 -Cont Drift and Sea-floor

Bell Ringer:
1) Please staple and turn in your
mushy mantle lab in the silver tray..
2) Take out the guided worksheet on
heat transfer from your blue tub. Put it in
your research divider and complete it. 8
minutes.
Today’s Lesson:
Continental Drift
(Drifting Continents)
Objectives:
1. What is continental drift?
2. How do landforms, fossils, and
climate changes show evidence
of the changing surface of the
Earth?
3. Explain how sea-floor spreading
provides a way for continents to
move.
Tech Terms:
1. Alfred Wegener –
German scientist whom in the
1900’s hypothesized that the
continents had once been a
huge landmass which he
called Pangaea (“all lands”).
Let’s fit the pieces of
Wegener’s puzzle
together!
Old book p. 118-122
2. continental drift – the slow
movement of continents over
Earth’s surface. It was a
hypothesis, that was tested.
Why did he believe in this theory?
3. fossil – any trace of an ancient
organism that has been
preserved in sedimentary rock.
Bell Ringer: Complete the back
of yesterday’s Review Sheet
Organizer!
• Define and illustrate the following
3 terms: Old book p. 118-122.
• Pangea
• Wegener
• Disbelief
• Wegener used evidence from
landforms, fossils, and climate to
support his hypothesis.
• Wegener’s hypothesis was
rejected because he could not
provide an explanation for the
force that pushes and pulls the
continents.
• Where is the math? How can you
recreate this experiment?
PBS Videos: Why Wegner
began his hypothesis!
• http://www.pbslearningmedia.org/resource
/ess05.sci.ess.earthsys.wegener1/platetectonics-the-scientist-behind-the-theory/
New Evidence
to support his claims?
• Cooling & Shrinking
• Sea Floor Spreading
• Molten Material and
Magnetic Stripes
• Convection Currents
So What’s Next?
• How does convection current movement
create continental drift?
• Continental Drift inside the mantle (2 min)
• TODAY’S Objectives! (p.123)
• What is a mid-ocean ridge?
• How is Sea Floor Spreading Related?
1. mid-ocean ridge – longest
chain of mountains extending
into all of Earth’s oceans, that
curves like the seam of a
baseball along the sea floor.
2. sea floor spreading – the process that
adds new material to the ocean floor
at the mid-ocean ridge. Molten
material erupts and spreads out
through the valley that runs along the
center of the mid-ocean ridge. It then
pushes aside the rock that was
already there.
It’s all about …
CONVECTION CURRENTS!!!!!!
Continental Drift inside the mantle (2 min)
3. deep ocean trench – this forms
from subduction
4. Subduction- (the oceanic crust
bends downward forming a deep
underwater canyon on the ocean
floor).
deep ocean trench examples
4. subduction – Part 2: when the
ocean floor sinks beneath a deep
ocean trench and gets swallowed
by the mantle.
Alaska
• Sea-floor spreading and
subduction can change the size
and shape of the oceans.
• The Pacific Ocean, aka The Ring of
Fire, has lots of subduction zones,
thus it is getting smaller.
• The Atlantic Ocean is expanding!
Further Evidence of
Continental Drift!
• http://www.pbslearningmedia.org/resource
/ess05.sci.ess.earthsys.wegener2/platetectonics-further-evidence/
So what will happen as these
plates in the ocean floor
continue to spread?
• Earth 100 Million Years from now
• Convection Currents in the Earth. One more
time, a different way!
• Plate tectonics on a cocoa earth - YouTube