Lab 2 Tectonic Plates
I. Using a pencil, drawn line on the seafloor to show where new ocean crust and lithosphere is forming now (zero millions of old). • years Id) Using Figs. 2.1, 2.3, and 2.12 as guides, label the segments of your line that are the Juan de Fuca Ridge and Gorda Ridge (divergent plate boundaries).
Then label the segments of your pencil line that are transform fault plate bound-aries. Add half-arrows to the transform fault boundaries to show the motion of the two plates relative to the transform fault.
2. What has been the average rate and direction of seafloor spreading in mm per year (mm/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 mm per year (mm/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 I I million years no longer exist on the seafloor east of the ridge?
5. Notice the black curve with triangular barbs just east of point
C: (a) If you could take a submarine to view the sea floor along this line, what feature would you expect to see? (Hint: See Fig. 2.1A.)
(b) Based on Fig. 2.1, what lithospheric plate is located east of the black barbed curve?
(c) Based on Fig. 2.1, what lithospheric plate is located west of the black barbed curve?
6. REFLECT & DISCUSS Notice the line of volcanoes that form the Cascade Range, extending from northern Califor-nia 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?
