As I slowly work on new new maps, while re-visiting older ones I've created, I've seen a theme that I obviously must like as I keep repeating it. Namely a passage that bisects (divides) a larger land mass, and is connected to separate oceans at either end. In some places this "sea lane" is wide (100+ miles) while other times it narrows and may be only a mile (or less) in width. I like not just the visual appearance this creates but I also enjoy imagining the economics, wars and migration patterns that it impacts.

As I looked at these maps and smiled at the similarities, I began to wonder about the different effects these passages would create. Massively strong water currents and winds in some locations, extensive banks of fog in others, rip tides etc etc. I looked to our world to find some similar locations, but really didn't discover any place that was similar. Locations such as the Mozambique Channel, English Channel or even the Sea of Japan are close, but none match the length or the significant land masses (on both sides) that I like to use.

So my questions are about these long channels. Do you have any "rules of thumb" for determining general currents? What of plate tectonics and the frequency of earthquakes? If the northern end opens into an arctic ocean, while the southern end is in the tropics, are we looking at area's of almost permanent fog where the the cold and warm waters meet? What do you think?