Page 75 - Laboratory Manual in Physical Geology

3. What causes the “lava” to move from the top of the lamp to the base of the lamp? (Be as specific and complete as you can.)

4. What is the name applied to this kind of cycle of change? ( Hint: Refer to FIGURE 1.6 on page 13.)

C. Observe the seismic tomography image in FIGURE 2.6 : a slice through Earth’s mantle at a depth of 350 kilometers. Unlike
the lava lamp that you viewed in a vertical profile from the side of the lamp, this image is a horizontal slice of Earth’s mantle
viewed from above. This image is also false colored to show where rocks are significantly warmer and less dense (colored red)
versus cooler and more dense (colored blue).

1. How is Earth’s mantle like a lava lamp?

2. How is Earth’s mantle different from a lava lamp?

D. Compare the tectonic plates and plate boundaries in FIGURE 2.5 to the red and blue regions of the seismic tomography image

in FIGURE 2.6 .

1. Under what kind of plate tectonic feature do the warm, less dense rocks (red) occur most often?

2. Under what kind of plate tectonic feature do the cool, more dense rocks (blue) occur most often?

E. REFLECT & DISCUSS Based on your work in B – D , draw a vertical cross section (vertical slice) of Earth that shows how
mantle convection may be related to plate tectonics. Include and label the following features in your drawing: mid-ocean
ridge (divergent plate boundary), lithospheric plate(s) with ocean crust, subduction zone (convergent plate boundary),
lithospheric plate with continental crust, arrows to indicate the convection motion of the mantle. Use colored pencils to show
where the mantle rocks in your vertical cross section would be red and blue like the false colored mantle rocks in FIGURE 2.6 .

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