Latitude can be easily determined by using sun angles and star sightings. assume you are using polaris ( the north star) as your frame of reference. what is the relationship between your latitude and the angle of polaris above the horizon?

If you are in the northern hemisphere, then the angle between Polaris and
your northern horizon is always within about 1/3 degree of your north latitude. 
For many purposes, it's close enough to just figure that the elevation of Polaris
above your northern horizon IS your north latitude.

Sadly, it's a different story if you are in the southern hemisphere ... Polaris is
never visible from there at all.

None of them. they are likely to occur on any plate boundary