The subduction is not at 90° to the NW-bearing scarp, but is at 70° - 75°. The scarp is believed to be rotating CW away from perpendicularity. Geologic history of the current regime Initially the trench was considered the surface expression of African and Eurasian plate collision. Such a view could not be verified because the trench was full of obscuring sediment, and because the arc-shaped Mediterranean Ridge seemed part of the subduction complex. If the strike of the subducting plate is in the Hellenic Trench (often termed “the classical view”), then it is far distant from the accretionary ridge supposed to have been accreted there. Subsequent data, especially earthquake, made possible other theories. Perhaps the bottom of the trench did not connect with (was decoupled from) the subducting plate at all but was a “pull apart” fault basin in the forearc (the raised chain of highlands and islands), or perhaps it was part of a wrinkle in the foredeep produced by compressional motion of the Aegean Plate against the “backstop” of the Mediterranean Ridge. Or, perhaps it was a normal fault, a “half-graben” produced by extension of the Aegean Plate. In these other theories, the subducting plate would start its subduction under the Mediterranean Ridge, and pass under the Hellenic Trench decoupled from it. However, it cannot be seen under the ridge. Moreover, the Hellenic Arc would not be the forearc, the edge of the Aegean Plate, but this edge would be hidden under the ridge. It would now be necessary to find a reason for the trench. Opinions vary. The search goes on. Historical geology offers reasons for hypothesizing that, in its earlier development, there was one trench traversing what is now the Aegean, and that it contained the subduction zone and the edge of the Eurasian Continent. The compressional regime If one imagines all the geologic changes brought about by extension to be reversed, then all the islands descend from an ancestral Hellenic Arc traversing the North Aegean. The Gulf of Patras was closed, as well as the Gulf of Corinth. Lefkadi, Ithaki, and Kefalonia were telescoped into a single ancestor. The Adriatic Plate and the Ionian Plate (under the Ionian Sea) were one. Zakynthos was in the line of islands at the edge of the future border between the two plates. Greece lacked its current projection into the Aegean; in fact, the Aegean was not there.