Wiktionary
midoceanic
a. That occurs in the middle of the ocean
Usage examples of "midoceanic".
They tended to cluster along the edges of tectonic plates grinding past or diving under one another—he knew that much at least—and they appeared along the midoceanic ridges, as well, which were tectonic plates pulling apart, stirring up a froth of magma from the mantle, which spewed up periodically in spectacular volcanic eruptions.