This sound effect can be found on the Lucasfilm Sound Effects Library, which was made by Sound Ideas. It includes SKYWALKER, EXPLOSION - BIG CRUNCH in multiple pitches. Links: https://soundeffects.fandom.com/wiki/Sound_Ideas,_ROCKS,_EARTHQUAKE_-_RUMBLE,_CREAKS,_CRASHES,_TUMBLING,_AVALANCHE#Audio_Samples