SOLVED. Sci-fi 90s earth megastructure ring, earth moving motors

[Alan]

It’s a good sized book from the 90s or early 2000s where the earth grows a belt of engines.

It's an apocalyptic story as the earth grows giant ridges to the edge of the atmosphere that contain giant planet moving engines. I vaguely recall people BASE jumping off these giant ridges.

I seem to recall it having a title like FLUX or something short and dramatic.

[Alan]

OK, I found it.

https://www.goodreads.com/book/show/7...

CUSP