AERLAAN – A playground built for a muse

[Pixie]

Looking forward to see your results, PaGaN. But no worries, this is a hobby - you just take good care of your mother-in-law first

Question for you though Pixie. Regarding ocean crust to ocean crust subduction, i know this is crucial for figuring our where ones island arcs are going to be, but i'm having trouble figuring out how oceanic crust ends up being subducted by oceanic crust.

Regarding this. Ocean-Ocean subduction exists in some places on Earth, most notably on the caribbean plate, the aleutian islands and the philipines plate. In all three cases one the plate staying on top is the remnant of a now inactive spreading-center (starter oceanic ridge), still, geologists are still struggling to spell out the details of their past lives.
Here's an article I found about the caribbean plate - it's technical, but have a look at the pics

In general, for the caribbean, imagine this:
1 - North America starts to split from S.America, forming an initial spreading center (a bit of oceanic crust eventually).
2 - These two continents were also splitting from Africa (and Europe, which split before), giving room to the Atlantic Ocean.
3 - Eventually, when they all end apart, crust from the Atlantic and crust from the Caribbean meet and one might end up under the other... (which happened!)