Download CONSTRUCTING A SEA-FLOOR SPREADING MODEL

Name _________________________________________ Date __________ Period _________
CONSTRUCTING A SEA-FLOOR SPREADING MODEL
PURPOSE: To demonstrate processes and features at mid-ocean ridges and at trenches.
BACKGROUND INFORMATION:
The lithosphere is composed of the crust and upper mantle and is broken into large pieces
know as plates. The lithospheric plates, carrying both oceanic and continental rock, “float” on the
plastic part of the mantle below the lithosphere. Plates move together, separate, and slide past each
other creating regions of volcanic activity, mountain building and earthquakes. The plates are
thought to be driven by a convection current mechanism that is deep within the earth.
The sea floor is spreading from the ocean ridges where new ocean crust is created and
spreads outward. Magma rises to the surface “filling in” the gaps left by the pull-apart fractures and
solidifies, forming new oceanic crust. Rocks directly next to the ocean ridges on either side are
younger than the rocks farther away. The youngest rocks are in the center of the ridges. A great
deal of activity—volcanoes, earthquakes, fault zones, trenches—take place along these ridges.
PROCEDURES:
1. Cut along the lines indicated on the Sea-Floor Model worksheet that
accompanies this activity. Color the areas indicated on the two strips.
2. Tape together the red ends of the strips. Fold this one long strip in
half at the taped seam, with the colored portion on the inside.
3. Pull the loose edges of the colored paper strip up through the Slit B of
the uncolored, larger piece of the worksheet. Pull one end of the strip
down through Slit A and one end through Slit C. See the sketch
below.
4. Practice moving the colored paper strips through the slits so that the same color “emerges” from Slit B at the same
time, and the same color “disappears” from Slits A and C simultaneously.
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DISCUSSION QUESTIONS/CONCLUSION: Answer using complete sentences.
1. What do the strips represent?
2. What do the colors of the strips represent?
3. What kind of plate boundary does Slit B represent?
4. What Earth feature forms at Slit B?
5. What kind of plate boundary do Slits A and C represent?
6. What Earth feature forms underwater when an oceanic plate slides under a continental plate?
7. If you were to sample and date the rocks along the colored strip starting at Slit B and moving
toward Slit A, what change, if any, would you observe in the age of the rocks?
8. If you were to sample and date the rocks along the colored strip starting at Slit B and moving
toward Slit C, what change, if any, would you observe in the age of the rocks?
9. If you could travel to the sea floor, would you? Why/why not?
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SEA-FLOOR MODEL WORKSHEET
_________________________________slit A
red
red
orange
orange
yellow
yellow
green
green
____________________________________slit B
_________________________________________slit C
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