How do continental plates move?
One of the models that helps explain how tectonic plates move is the convection model.
In this hypothesis, the molten magma of the mantle boils like water in a pot. The pattern of the
moving water forms a circular wave or current as hot water rises to the top and cooler surface
water is forced to the side of the pot and back down to be heated again. Inside the Earth it is
believed there are many convection cells, or regions in the mantle, that boil like this. The
different cells have their own currents and constantly move independently of one another. The
crust of the Earth has a much lighter mass and density than the magma. As a result, the plates of
crust are moved by convection currents and broken up on a the boiling surface of the mantle
Purpose of Activity:
Students will model convection currents and the movement of tectonic plates.
Materials:
Bunsen Burner
Wood shavings
scissors
tongs
water-500ml
beaker tongs
spoon
rice
750ml beaker
Procedures:
1.
2.
3.
4.
5.
6.
7.
Carefully light the Bunsen burner and adjust the flame. Fill the beaker 2/3 full (~500ml)
of water and place it on the hot plate. It will take a while for the water to boil.
When water comes to a boil carefully add two spoonfuls of rice to the water.
After adding the rice carefully add your wood shavings. If the water has any steam or
tiny bubbles at the bottom of the pan. (be very careful not to splash any water)
As the water heats, watch the action of the bubbles and rice as they rise from the bottom
of the pot. Record your observation in the table provided (next page)
Once the water begins to boil, watch your pieces of wood shavings. Think about these
questions. How do they move? In what direction do they go? Do they stay in one place
in the pot or do they move? Record your observation in the table provided (next page)
When the experiment is over, turn off your Bunsen burner.
Record your observation in the table provided (next page)
Data and Observations
Actions of the bubbles 1.
and rice
Movement of the
wood shavings on
boiling water
2.
Sketch your observations in the space below
Figure 1 illustrates the plate tectonic model of the Earth. Draw convection cells on the
asthenosphere that explains the movement of the Earth’s plates.
Questions and Conclusions
1. In comparison to the Earth’s structure, what does the following represent in this
model?
a. Beaker _________________________________
b. Flame __________________________________
c. Water and rice____________________________
d. Wood shavings ___________________________
2.
Explain the motion of the water and the rice using changes in density as the basis of
your explanation. ______________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
3.
Where was water constantly being moved/brought to the surface? ________________
_____________________________________________________________________
4.
Describe the movement of the wood shavings when the water started to boil. Could
you see a pattern? ________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
5.
How does the experiment model the moving tectonic plates? ____________________
_____________________________________________________________________
_____________________________________________________________________
6.
In comparison to the Earth’s structure, what kind of plate boundary does each of the
following represent?
a. Region above the flame __________________________________________
b. Region opposite of the flame _______________________________________
7.
If new material is always emerging from divergent plate boundaries are the plates
continually growing bigger? Explain your answer. ____________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
8.
Predict what would happen if the convection currents of the molten magma changed
directions ____________________________________________________________
____________________________________________________________________
____________________________________________________________________
or stopped altogether? __________________________________________________
_____________________________________________________________________
_____________________________________________________________________
9.
Which theory in our book best fits the observations you made today in the lab?
Explain why this theory best fits your observations. ___________________________
_____________________________________________________________________
_____________________________________________________________________
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