Vitrified Glaze and MELT on SACSAYHUAMAN and nearby peaks!

Why is Sacsayhuaman all melted away? What's going on? 

I have been reading some Eric Von Daniken lately.... in two books, Return to the Stars and also Pathways to the Gods, he mentions that the fortress above the famous walls of Sacsayhuaman are more interesting than what the tourists are looking at... the huge stones... because it's all melted up there! 



The tops of Sacsayhuaman and nearby peaks have this vitrified 'sheen' to them, which is rather difficult to explain. Parts of the top of the fortress are completely melted. 

1) If it was lightning which caused the meltage, why was this not attracted to the higher peaks nearby? What's going on? 


2) Was it ancient thermonuclear weapons? If so it was the last gasp of an attack because Sacsayhuaman, though built well, is not built on some modern highly-geometric design, more like by some vestige of a former high civilisation which retained their geopolymer knowledge, but little else. They built this high fortress in the hills to escape from the savage unfriendly tribes below. Yet the walls are strong enough to deflect artillery. Could they have been vitrified by remnant nuclear weapons from suborbital platforms on 'autofire?' 

We look at the nearby peak which is called 'The Throne of the Incas', in this it appears the glaze or vitrification is confined largely to the worked areas, which means it could be a feature of the workmanship. It is actually hard to find pictures of the melted areas as these are simply ignored by tourists in favour of the better less damaged areas... i'd rather not directly use pictures from any book, prefer pictures already online.