Borup Fiord Pass is a glacier-carved valley on Ellesmere Island in Nunavut, Canada. The valley contains a natural spring which carries fluids from the subsurface to the surface, sometimes passing through the glacial ice in the process. The spring is the only known place where sulfur from a natural spring is deposited over ice.[1] At the Borup Fiord Pass spring, hydrogen sulphide gas in the water is converted to stable deposits of either elemental sulfur, the most common material in the deposit, or gypsum.[1] The process by which hydrogen sulfide becomes sulfur is complex, and most often occurs when microbes, like bacteria, are present.[1]
To the south the pass leads into Esayoo Bay, part of the Borup Fiord.