Complex sentence: An unnamed glacier known colloquially as Larrabee Glacier lies below the steep north face, and below that glacier is the Boundary Red Mountain Mine where gold was discovered in the early 1900s.
Split into simpler sentences: An unnamed glacier known colloquially as Larrabee Glacier lies below the steep north face. Downslope of that glacier is the Boundary Red Mountain Mine where gold was discovered in the early 1900s.