Download "Seafloor Spreading" Lab

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Names____________________________&________________________________Bl___Date___!
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your name (first and last)
partner!
Sea Floor Spreading Lab ES2 # 2!
Purpose: Show rock age and magnetism patterns in spreading sea floor with a paper model.!
!Background: In the last few decades, scientists have discovered both age and magnetic patterns in the seafloor,
Plate!
Tectonics
which is further evidence for plate tectonics. This evidence shows that new seafloor has been forming for millions
of years at mid-ocean ridges throughout the oceans. Magma melted within the crust rises to the seafloor, cools
and solidifies into new rock. In some places this new seafloor is pulled apart by movement of the asthenosphere
under the plates, forming two rock masses which move slowly apart from the ridge. Geologists call this seafloor
spreading.!
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Elsewhere, one plate slides under another, or subducts, and deep ocean trenches are formed. This is called a
subduction zone and happens at converging boundaries. Rock on the subducting plate becomes part of the asthenosphere. Oceanic crust is denser and thinner than continental crust, so all seafloor rock is eventually destroyed in this way. Thus, the oldest seafloor rocks are only 180 million years old, but the oldest continental rocks,
which aren’t dense enough to be pulled into the trenches, are as old as 4,000 million years, or 4 billion years.!
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yay, bonus pt. because ________ !
oops, no HO, book, heading on
this date______=MP
Pre-lab thinking. Read the Background above!
1. What pulls the new seafloor apart in opposite directions?___________________________!
2. Where are trenches formed?______________________!
3. How old is the oldest seafloor?____________ the oldest continental rocks?______________!
Why are the continental rocks so old?!
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Procedure: Given a model? skip to #1. If you need to make a model, ask Mrs SF for a Prentice Hall textbook and consult pg. 131 Pull off pages 4 & 5 of lab. Make these changes to step a & b.!
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a. The stripes are already drawn across the rectangle on the next page. If needed, color the 4 sections of the
rectangle as labeled, and put your name on the strips. Color lightly, and don’t take too long, it needn’t be perfect.
b. Tape the yellow ends together. !
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1. Is the rock represented by the yellow strip the oldest or youngest?_________________!
MU (only do if incorrect on or missed original question) Explain how you know:!
2. Is the mid-oceanic ridge at SLIT B or SLITS A& C? ________ !
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Circle one: At this boundary are plates coming together or pulling apart?!
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Is this called converging or diverging?_______________!
Circle one: With lava emerging at this boundary are the mountains formed volcanic or non-volcanic?!
MU Explain how ridge is formed:!
3. Is the rock shown by the blue strip the oldest or
MU Explain how you know:!
map = 12 ____ total wrong/50 @ 2 ______
grade = _________ F, Ex, Complete for_____.
Do ____ MU (see front] for____ Make appt for
to do, finish, for help_____MCGC CIC L FL
Forgot grade abbreviations? See class sign,
youngest?____________________!
Ipass progress report “comments to class”, ES1
or ES2 home pages on Mrs. S-Fs website. Do
corrections in another color.
4. Is the subduction zone with ocean trenches at SLIT B or SLITS A& C? !
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Are the plates at this boundary converging or diverging? _____________!
MU Explain how trench is formed:!
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5. New seafloor rock is continually being formed at mid-ocean ridges and destroyed at!
trenches in subduction zones. Rock is formed on the continents, but then pushed up into mountains. Which rock
will be older, continental or ocean floor?________________MU Explain why:!
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6. Ocean plates slide under continental plates.!
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Which are denser, oceanic plates or continental plates? ________________ ! !
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Which are thicker (Review background material on front if needed)? ______________!
MU Give average thickness of each with measurement unit (use textbook to research):!
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7. Look at the white map, which is part of the lab and look at the map key at the bottom. Pick a color for convergent boundaries and fill it in below. Draw what the map symbol looks like:_______ Color the length of all convergent boundaries that color on the map. Look carefully! Are the plates coming together, spreading apart or sliding
by each other?__________!
If needed, consult pg. 282 and 284 Color picked: !
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5 of these features are formed at convergent boundaries. Remember that earthquakes can happen wherever plates move. Circle the 5 features: !
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volcanic islands
! trench !
mid-ocean ridge !
earthquakes new sea floor
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volcanic mountain chain!
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rift valley
non-volcanic mountain range !
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MU Explain how two are formed!
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8. Repeat st.7 for divergent boundaries. Use different color
Draw the 2 map symbols:_______ or ______!
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Are the plates coming together, spreading apart or sliding by each other?__________!
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5 of these features are formed at divergent boundaries. Circle them: !
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volcanic islands
! trench !
mid-ocean ridge !
earthquakes new sea floor
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volcanic mountain chain!
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rift valley
non-volcanic mountain range!
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MU Explain how two are formed!
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9. Color the transform boundaries a third color on the map and key.
Draw the map symbol:_______!
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Are the plates coming together, spreading apart or sliding by each other?_________!
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Earthquakes happen at transform boundaries, and anywhere there is moving rock. If needed, consult
pg. 284 on transform boundaries. What is caused by the plates rubbing together that produces earthquakes?
(Rub your hands together to find out)____________________!
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At what other common boundary types do these earthquakes occur? ____________________ &
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MU Explain cause of earthquakes--see text and notes !
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10. What kind of mountains are formed from the magma emerging at the ridge when 2 pieces of ocean crust
separate, volcanic, or non-volcanic?_____________________!
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MU Explain why:!
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Circle the Mid-Atlantic Ridge, and Iceland on your map. Done___ What kind of boundary is this, divergent or convergent?_____________________. Look at Iceland carefully on the map. What is under this island
that makes it grow quickly?_______________ If needed, consult pg. 334!
MU Explain how you know!
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11. How are the magnetic stripes formed on the ocean floor and why are they the same on either side of the midocean ridge? 2 pts If needed, consult pg. 278!
Give a new fact you learned, or question you still have about seafloor spreading:!
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EXTRA CREDIT: Something in my life which is connected to any of these ideas:
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Briefly explanation earth science connection with any of these concepts!
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Done early? ask for the Seafloor Spreading Rifting Continent extra challenge questions...!
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