1. Neither ocean basin nor continent are permanent features on the planet. The earth continues to change as one plate collides with another creating changes in the continent and the ocean basin.

3. Pole reversals are periodic reversals on the earth's magnetic field. i.e. the north and south magnetic poles swap directions. As molten rock solidifies certain minerals align themselves with the earth's magnetic field. Since pole reversals can be calculated, dates can be determined on when the rock was formed, or what rocks formed at the same time. Also, if we know the age of the rock, its movement can be determined by a comparison of its mineral alignment and the magnetic field when it formed.

6. Studies of the alignment of the minerals indicated that the poles wandered all around the globe (as opposed to a simple north-south switch). It was then suggest that the continents moved rather than the poles.

9. If the Hawaiian Islands are the tops of huge volcanoes that formed as the floor of the Pacific Ocean moved over a stationary hot spot, then the oldest islands are furthest away from the hot spot. One can trace the motion of the plate by connecting the islands with a pencil. Which way is it moving?

10. (p. 600) Ions within the outer core are moved through convection currents (p. 163).

11. Crust is created at spreading centers (divergent plate boundaries) and destroyed at subduction zones (converging plate boundaries). They are considered in equilibrium because it is believed the earth is neither expanding or contracting.

12. Ocean crust is more dense than continental crust and thus sinks when the two are forced together.

1. The Richter Scale is logarithmic, like the pH scale. Each log unit is an order of magnitude, i.e. log unit is 10, two log units is 100 (10²), three log units is 1000 (10³), and so on. So, an earthquake measuring 8 on the Richter Scale (eight log units is 100,000,000) has an amplitude 100 times that of an earthquake measuring 6 on the Richter Scale (six log units is 1,000,000). We can calculate this using 10^8-6 = 10² = 100.

2. Recall distance = rate*time or time = distance/rate. 3.5 cm = 3.5 x 10^-5 km;

time = (600 km)/( 3.5 x 10^-5 km/yr) = 17142857.14 years, over 17 million years.