Music score.
I remember this episode having a very good music score to it, particularly during one scene. I've heard a sample on the Varèse Sarabande: A 25th Anniversary album but it seems to use a lighter tone compared to the more powerful one in the movie.
The score to this scene, I am on about where Indy and his father are climbing back up to safety. The crescendo is really good.
http://www.youtube.com/watch?v=PXXMnR_XnI0
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Thorpe89