Bricks, Masonry, Asphalt and Concrete - Glass block walled skylight

I live in an odd part of Spain where the house roofs are flat and made of chestnut log beams spanned by a type of random slate and covered in Launa which is a sort of fine micacious rock/earth including a waterproof membrane. (It does work!) Mine is pierced over the internal stairs by a skylight about 1 metre square. It consists of a low rendered wall (about 20cm) capped by a VERY thick piece of wired glass. The glass is cracked and leaks in heavy storms (I am over 4000 ft above sea level.) Some locals claim it was caused by seismic vibrations which is possible but I think thermal stress is more likely as it is layed directly on the wall with overhang. I want to repace or build up the wall with glass blocks (1 possibly 2 courses) and cap the top with a single piece of the local slate (about 5/10 mm) Any ideas or observations on the construction method or do I need Psychiatric help?

I think you are talking about a roof, although you mention "wall". Glass block can't be installed horizontally. There is no support between the block to keep them from collapsing. True, seismic movement may have contributed to the crack, but if the glass is not tempered, heat could have come into play. I think the simplest solution would be to replace it with a similar wire mesh glass (tempered this time). Since your opening already is set for that type glass, minimal modification would be necessary. Good luck with it.

Or even Plexiglas™ or Lexan™. Yes, will scratch but should hold up. (Not sure about UV resistance though on second thought.) Do know something similar is used in place of plate glass store windows.

Here in the States ready made skylights are available. Maybe they are where you are too.