Douglas Trumbull has video commentary at his website where he explains the creation of the "Hades" landscape from Blade Runner. It's the first in a three-part series about the movie's groundbreaking special effects. From the website:
Doug reveals how the explosions visible in the sequence were projected on screens placed throughout the miniature and light-timed. These explosions were created through massive pyrotechnics shot in the California desert for a discarded sequence for the 1970 Michelangelo Antonioni film Zabriskie Point.