Crevice is known as a fracture or split caused by nature on a rock surface.
"We noticed a crevice on the huge rock while hiking."
Crevasse on the other hand is a deep fracture on a glacier or ice sheet. It is common for both words to be used interchangeably, but that is very wrong and unacceptable.
"It is not uncommon to come across a crevasse in the Antartica."