Geology 15                                                                                          Summer, 2000

West Valley College                                                                         R. Lopez


Study Question 2

Plate Tectonics and California


1)      What does the word “tectonic” mean?

2)      How long in terms of millions of years has California faced the Pacific Ocean?

3)      Who proposed continental drift?  What was the name of the supercontinent that formed at the end of the Paleozoic and into the early Mesozoic?

4)      State the three basic concepts of plate tectonics?

5)      Draw a simple cross section of the Earth roughly to scale and label the crust, mantle, and core. Know the approximate thicknesses of average oceanic and continental crust, but you do not need to know the exact thicknesses of mantle and core.

6)      What is the Moho? How did geophysicists determine the depth to the Moho?

7)      What is the difference between the inner and outer core?

8)      What is the difference between the asthenosphere and lithosphere, and approximately how thick is the lithosphere? (Recall that the lithosphere includes both the crust and uppermost mantle and that the lithosphere forms the plates of Plate Tectonics—i.e. the base of the tectonic plates is the base of the lithosphere.)

9)      What do geophysicists call the asthenosphere (based on seismic wave slow down)?

10)  Be able to briefly discuss the three types of plate boundaries.

11)  How and where is new oceanic crust produced, and what is the process called?

12)  What is the definition of seafloor spreading?  Who proposed seafloor spreading?

13)  Label the Mid-Atlantic Ridge and East Pacific Rise, and know their approximate spreading rates.

14)  Sketch a convergent boundary, and include the subduction zone, descending lithosphere (oceanic crust and upper mantle), trench, ascending magmas, and magmatic arc.

15)  What is magma? And what causes magmas (i.e. volcanic activity) to occur at subduction zone settings?

16)  What is the difference between island arc and continental arc (Japanese type vs. Andean type)? At various times in the past, California was one or the other.

17)  What is the Benioff zone? Both the largest and deepest earthquakes occur at subduction zones.

18)  What type of earthquake was the 2004 Sumatra-Adelmen Is. Earthquake?

19)  The Cascade volcanoes Shasta and Lassen Peak are the result of the subduction of which plate?

20)  What is mélange?

21)  Transform boundaries are strike-slip faults. How do you distinguish right-lateral from left-lateral movement on strike-slip faults?

22)  The San Andreas is a transform boundary between which two tectonic plates? What is the sense of movement? Does the San Andreas transform take up all the motion between the two plates? In not, approximately how much and how is the rest of the plate motion absorbed?

23)  What causes plates to move?

24)  What are hot spots? How are volcanic chains produced by hot spots? What is the most famous chain of hot spot related islands, and where is the hot spot now?