1. Sea-Floor Spreading

2. Mid-ocean ridge
An underwater volcanic mountain range located midway between two continents; and encircling the globe.
**Figure 13.1

3. *There are two types of crust - continental crust and oceanic crust
*Sea-floor spreading
- the process by which new rock is formed from magma emerging from the mid-ocean ridge
- Creates crust
**add picture of ocean floor**

4. 6.85 miles below sea level Trench A deep valley on the ocean floor
Generally located near continents
The deepest is in the Pacific Ocean, Marianas Trench
6.85 miles below sea level
The creation of new oceanic crust along the mid- ocean ridge is matched by the destruction of the crust at the trenches.
**figure 13.3

5. Fault Zone
Concentrated areas of faults, thousands of kilometers long and hundreds of kilometers wide, forming cliffs up to 3km (1.8 miles) high