Evolution of the interior composition structure of an example single-star model with an initial mass of 11 M_⊙ after core oxygen depletion. From diagrams 1 to 3, core silicon burning occurs, leading to the creation of ⁵⁴Fe. The silicon-burning shell of the star merges with the oxygen-rich layers above, between points 4 and 5, leading to the creation of ²⁸Si, ³²S, ³⁶Ar, ⁴⁰Ca, and ⁵⁴Fe in the oxygen-rich layer. From points 6 to 9, the outer layers of the silicon-rich region turn into iron-group elements.