This block of land of Vlachopoulo shifted relatively down versus two other blocks, called a graben.
A graben is a depressed block of land bordered by parallel faults. Graben is German for ditch.
A graben is the result of a block of land being downthrown producing a valley with a distinct scarp on each side. Grabens often occur side-by-side with horsts.
This area also belongs to a plateau area of marl.