Somewhere between 3500-4000 tons of munitions exploded, mostly High Explosive bombs but including up to 500 million rounds of .303 ammunition.
The resulting crater was 400 feet (120 m) deep and ¾ mile across (1,200 m). It is still visible today and called the Hanbury Crater.
At the Time
Today
The cause at the time was vague, Italian POW’s were working in the depot and it is thought a prisoner may have dislodged a bomb fuse. No one will ever know.
Incredibly the death toll was very light considering the size of the explosion, 26 killed at the Depot, 37 killed (some drowned) at a nearby plaster factory that was demolished in the explosion..
http://en.wikipedia.org/wiki/RAF_Fauld_Explosion is a good introduction.
I would be curious to know, did the explosion have any impact on Bomber Command operations for the next few months?