Modeling Convection in the Mantle
*do not write on this sheet*
Part I: Convection Currents in Rheoscopic fluid
Materials:
 A jar of rheoscopic fluid, candle, flashlight, and blocks to rest the jar on
Procedure:
1. Collect the materials that are needed for this lab. Observe the materials and the fluid that is inside your
jar.
a.
What observations can you make about the fluid (record in notebook).
2. Set-up your materials by taking your jar and placing on the
blocks given. Place the candle underneath the jar after your
teacher lights the candle. (look at the figure to the right)
3. Shine the flashlight on the fluid and observe the movement of
the fluid and what happens. You may need to stand up to see
what’s happening on the top of the jar. Can you follow the
movement with your flashlight?
a.
What did you observe when you place the flashlight on the jar? (record in notebook)
b. Glue the diagrams given to you by your teacher to your NOTEBOOK.
c.
Draw arrows on the diagram in your NOTEBOOK to show the movement of fluid within your jar.
Then label the parts of the picture that represent the mantle and core of the Earth’s interior.
Part 2: Model of Convection Currents in the Earth using Food Coloring
Materials:
 A plastic container (shoe box size), 2 Styrofoam cups, 2 eye droppers/pipettes, small cup of blue food
coloring, small cup of red food coloring, hot water and ice
Procedure:
1. Place white paper on your table. You will be setting up your experiment on this paper.
2. Fill plastic container ½ full with tap water (from sink).
Plastic Container (side view)
3. Fill one Styrofoam cup with ice and another Styrofoam
cup with hot water (teacher will pour this for you).
4. Place plastic container on top of cup with ice and cup
with hot water as shown in diagram.
5. Allow the water to sit for a few minutes.
Hot Water
Ice
6. Fill pipette/eye dropper with a small amount of BLUE food coloring. Place pipette in water so it’s almost
touching the bottom of the container in the center of the cold water cup. Release 2 drops from pipette.
Remove pipette. Make observations of what’s happening to the BLUE colored water. Use blue colored
pencils to draw what’s happening in the diagram below.
7. Fill pipette/eye dropper with a small amount of RED food coloring. Place pipette in water so it’s almost
touching the bottom of the container in the center of the hot water cup. Release 2 drops from pipette.
Remove pipette. Make observations of what’s happening to the RED colored water. Use red colored pencils
to draw what’s happening in the diagram below.
Modeling Convection in the Mantle Demonstrations (Student Sheet)
Read the passage below and answer the questions:
The earth has several major layers – a hot metallic core, a less hot
liquid mantle, and the solid lithosphere and crust. The hot metallic core
causes the mantle immediately above to heat up. As the liquid rock in
the mantle heats up, it rises because a heated liquid (or gas) expands
and becomes less dense than the cooler liquid (or gas) nearby. When
this hot liquid reaches the top of the mantle layer, it gets pushed aside
by more hot mantle rising below it, spreading out under the solid
lithosphere above like a cloud of steam hitting the ceiling of the
kitchen. As it spreads out, it cools. Cool liquids (and gases) shrink in
volume and are more dense than the warmer liquids (or gases) nearby.
Therefore, the cooled mantle sinks to the bottom of the mantle layer where it gets heated by the core and begins
the cycle anew.
Convection currents can occur in any fluid, such as air or a liquid. When a fluid heats up, it expands, making it less
dense and therefore lighter than the fluid around it. Warm fluids rise while cold fluids sink, setting up a circular
pattern of flow toward and away from a heat source until all of the fluid reaches the same temperature.
A key concept is that hot fluid and gas rises and cold fluid and gas sinks.
Part I: Convection Currents in Rheoscopic fluid (demonstration)
1. What observations did you make of the heated fluid?
2. Under what conditions could you observe convection cells forming inside the jar? How did they move?
3. What happened to the fluid near the upper surface of the jar (parallel to the table)?
Part 2: Model of Convection Currents in the Earth demonstration using food coloring
1.
Why did the water behave the way it did in the model?
2. What causes the convection currents? How do they form? (use the reading above!)
3. Where in a convection cell is the densest materials? (top or bottom)
4. What powers convection current in Earth?
a. Different temperatures in Earth’s layers
c. Volcanic eruptions
b. Different elements in Earth’s layers
d. Earthquakes
5. This experiment is a model for processes that occur within Earth’s mantle. What is the heat source driving
convection currents in the Earth’s mantle?
a. the crust
b. the outer core
c. the mantle
d. the inner core