Question Regarding Long Sea Channels

[Khairn]

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?

[ravells]

The only one I can think of which isn't made made (Panama / Suez Canals) is the straits of Gibraltar, but I think you're looking for something longer than that? No idea about how the currents would though.

[Ghostman]

About the only kind of natural phenomenon (that I can think of) that could cause a long channel between large landmasses is the divergence of tectonic plates (convergence wouldn't create a channel unless the coastlines of the converging continents happen to match, which would be an extremely unlikely coincidence). Unfortunately, it seems that even a split in a continent caused by diverging plates would not actually create a long narrow channel. A look at the Great Rift Valley gives the impression that such splitting is anything but tidy; you're likely to see parts of the channel end up as wide as the Red Sea by the time the thing has become continuous from coast to coast.

Then again, I'm no geologist so don't take anything I say as more than amateurish speculation

[jbgibson]

If you're not picky about the definition of "large landmass", the passage behind Vancouver Island might be instructive. It looks like "drowned topography". Hmmmmmm ... so all you need is a bit of flat connecting some nonflat landmasses, erode some rivers that almiost cut the isthmus, then raise the water level. Voila: river valleys become an ocean strait, and the River Poilice can't do a thing about it :-).

Again, the Strait of Magellan is continent vs. island, but Tierra del Fuego is pretty big, and the passage is mighty skinny. And the Drake Passage south of Cape Horn is a certifiably lousy piece of ocean to traverse, so the horrible conditions of the Strait of Magellan have long been one choice of mariners. And it looks like fjiordland - really rough terrain, that got itself drowned.

Tectonically, how about if a subduction trench at the edge of an ocean got "stuck", and the ocean plate diving under the continent bulged upwards? Or what if the ocean plate being subducted was carrying some continent, complete with continental shelf dropoff - when the two get close for a little while (geologically) you could get abrupt dropoffs opposing each other - not only narrow but Way Deep.

Suppose the Great Rift Valley of Africa (equivalent) were open to ocean... how much of a sea level rise could YOUR planet get, if you melted all of a super-Antarctica ice cap?

[Korash]

You might also want to look at the Falkland Islands. I have attached something that I did a while ago but left the layout of the islands as is in RL. True, the scale is not on a continental scale, but it does match your channels quite nicely.