Page 77 - Laboratory Manual in Physical Geology
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2. What has been the average rate and direction of
seafloor spreading in cm per year (cm/yr) west of the
Juan de Fuca Ridge, from B to A ? Show your work.
3. What has been the average rate and direction of
seafloor spreading in cm per year (cm/yr) east of the
Juan de Fuca Ridge, from B to C ? Show your work.
4. Notice that rocks older than 11 million years are present west of the Juan de Fuca Ridge, but not east of the ridge. What
could be happening to the seafloor rocks along line segment C-D that would explain why rocks older than 11 million years
no longer exist on the sea floor east of the ridge?
5. Notice the red line running through point C:
a. If you could take a submarine to view the sea floor along this line, then what feature would you see? (Hint: see
FIGURE 2.2 .)
b. Based on FIGURE 2.1 , what lithospheric plate is located east of the red line at point C ?
c. Based on FIGURE 2.1 , what lithospheric plate is located west of the red line at point C ?
6. REFLECT & DISCUSS Notice the line of volcanoes (Cascade Range volcanic arc) running from northern California
to southern Canada. These are active volcanoes, meaning that they still erupt from time to time. What sequence of plate
tectonic events is causing these volcanoes to form?
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