Talk:Hellenic arc

Some impossible supported content

The article relates that the Helenic Trench is not the suduction zone or the edge of the plate. I managed to look that one up, and the source says:

"In the 1970s, the linear deeps of the Hellenic Trench south of Crete were interpreted as being similar to trenches in other subduction zones, but, with the realization that the Mediterranean Ridge is an accretionary complex, it became apparent that the Hellenic Trench is actually a starved fore arc basin, and that the plate boundary lies south of the Mediterranean Ridge."

I don't know to whom it became apparent but no one else has this point of view. I do not know what the question with the Hellenic Trench was that it needed to be compared to other oceanic trenches to determine what it is, as the trench itself is a primary example. Why the accretionary ridge should change anyone's mind is totally unclear. The accretion is obviously from the south, not the north, unless sediment can somehow jump out of trenches to land on the slope above. Exactly what the author thinks is the purpose of the foredeep remains a mystery. How did it get to be so deep except by subduction? Why would the edge of the plate not be in the deep but be on the slope above? The ref dates to the 1970's, but that is no excuse. I do not fault the editor, as he supported his statement with this ref. I think we are dealing with a bad ref here, maybe some undergrad paper bundled in with some others. If it appeared in Wikipedia it would never be acceptable; nothing is explained. The very ridge brought forward as proof is proof of the statement's falsity. Something is not right here. So, I am commenting the statement out for the moment. The section and the article need a lot of work, which I am going to put in on this little group of stub geologic atricles. I rewrote the intro but the topics need development in the body. So that is what is going on here. Feel free to comment if interested.Botteville (talk) 22:49, 12 December 2020 (UTC)

The very next statement is just as bad also so I am commenting that out also. This is a misapplication of the ref given, which concerns the western Mediterranean Ridge. No page number is given and I cannot find any backthrust in there. The main thing is, our ridge is in the eastern med, not the western. The eastern differs by being the seat of vigorous back-arc extension. I hope thst is not what the editor meant by "backthrust" as the effect of the extension is to move the original arc and trench to the south, not to create some other. The remaining section is a bit scanty, but better that than wrong. I appreciate someone throwing in all these geology stubs but I find they usually have major errors Botteville (talk) 23:06, 12 December 2020 (UTC)

I wrote most of the content being discussed above. Could it be improved? - undoubtedly. Is the idea that Hellenic Trench does not represent the surface expression of a subduction zone (like the Middle America Trench or Marianas Trench) do) some short-lived proposal? - no it isn't. The Hellenic Trench is considered to be a set of fore-arc basins, most likely formed by the break-up of the original forearc by multidirectional extension. To quote a recent paper (Gallen et al. 2014) "The leading edge of the subduction zone is obscured beneath a thick package of sediments and is often misidentified as the more inboard bathymetric depressions known as the Hellenic troughs, but it is actually located outboard of the Mediterranean Ridge accretionary complex, ~150 km south of Crete" Yes, slightly more indirectly, the trenches are a result of subduction, but they are not subduction trenches in the normal sense of that term. Thanks for pointing out that the citation that I used for the backthrusting was not explicitly in support - although the maps show it clearly enough. I will find better sourcing for that. It's never a bad thing to revisit an article that was created to fill a gap, as there is plenty of material to expand and improve it and geologists keep on writing papers about it. Mikenorton (talk) 11:16, 13 December 2020 (UTC)