The (in)famous "opening of the Ark" sequence from the finale is incredibly jarring for a viewer who has thus far enjoyed an action/adventure movie with a relatively light tone. The shot of a head imploding on itself, followed by a melting face (pictured) - quickly followed by an exploding head - would have been enough to give plenty of theatre-goers nightmares.
The moment the spirits that emerge from the Ark turn hostile is utterly nightmarish. At first, they're serene - even beautiful, as Belloq declares - and then they suddenly start to shift into skull-face terrors, snarling at those daring to look upon the open Ark.
On top of the visual horror, the sound of Dietrich's head imploding. You can hear his brain matter turn to goop and his bones crunching! To further add to the nightmare fuel, there's the horrific hissing sound Toht's boiling blood makes, coupled with his screams getting muffled by the gurgling of his mouth filling with blood. And those screams continue as he becomes skeletonized.Sweet dreams...
Of all the things to remain in Area 51, the Ark is the only one that should be there. If you ever read the Bible or listened to Indy's warning, it's made pretty clear that you should NEVER OPEN THE ARK!
Earlier in the film, a Giant Mook is chopped up by the propeller of an airplane and while it happens off-screen, the copious amounts of blood on-screen are jarring, considering the Ark scene aside, the film is rather light on blood.
It's never made clear, but in the long shot of the plane shortly before it explodes, a large smear across the sand with some chunky bits is seen near the plane....