Complex sentence: An explosion from the ignition of a build up of flammable and poisonous methane gas caused by sparks from a fan control box ripped apart the busiest pit in late Tuesday night 24 July 1979, and caused a series of fires in the mine's damaged ventilation system.
Split into simpler sentences: An explosion from a build-up of methane gas ripped apart the busiest pit in late Tuesday night, 24 July 1979. This build-up caused a series of fires in the mine's damaged ventilation system.