5.6a: sketch, label, and explain an oceanic divergent boundary (mid-ocean ridge).
5.6b: sketch, label, and explain in four stages how continental rifting can lead to the formation of a new ocean basin.

The nature and degrees of rifting can lead to the formation of a new ocean basin as explained by the phases below.

Explanation:

Continental mass when pulls apart are called as rifting or drifting away from the main landmass. Development of rifts can be seen as  

1. Rift Initiation: In which the upper part of the lithosphere starts to extend, as a series of unconnected normal faults. Which leads to the development of isolated basins.

2. Mature Rift stage: As the rift evolves some of the individual fault segments continue to grow and form larger boundary faults. As subsequent compression becomes concealed on these faults. Larger faults become wider and as a result, the earth's surface is raised and crust becomes thin and heats the mental from below.

3. Post rift subsidence: Once the rifting cool and stops the amount of subsidence s directly related to the amount of thinning of the rift phase which is calculated as a beta factor and affects the degrees to which the sediments are filled by the rift.

4. Multiple rifting: This is a complex and prolonged history of rifting with an example of the North sea drift. Usually occurring over 100 years.

B. California's admission threatened to upset the balance of free and slave states.