The stream mostly follows an unusually long, straight, narrow, and steep-sided valley, between the Jordan Ridge to the south and the San Juan Ridge to the north.[2] This valley is the surface trace of the Leech River Fault, a major regional fault that marks the contact between the oceanic basalts of the Crescent Terrane (part of Siletzia) to the south, and the metamorphic rocks of the Pacific Rim Terrane to the north. The Leech River fault is straight because it was originally a strike-slip fault (moving horizontally), but now it is being thrust under Vancouver Island. As the Pacific Rim rock is uplifted and exposed it rapidly erodes; this releases the occasional gold deposit, which then collects in placer deposits in Loss Creek.[5][6]
Loss Creek begins at an unnamed confluence at a point north of the settlement of Jordan River at an elevation of 507 metres (1,663 ft).[3] It flows west for 14 kilometres (8.7 mi), taking in the right tributaries Gain Creek and Noyse Creek, passing under Highway 14, and taking in the right tributary Jack Elliott Creek. It then turns south for 2 kilometres (1.2 mi), flows under a suspension bridge carrying the Juan de Fuca Marine Trail,[7] and ends at the Strait of Juan de Fuca on the Pacific Ocean, east of Sombrio Point[8] and south east of the settlement of Port Renfrew.[1][2][4] The average slope is 3.2% over 16 km (507m/16000m=0.03169). Rapids of 12% slope exist near the mouth of the tributary Gain Creek. The steeper the slope the higher the uplift versus erosion. This indicates an anomaly of uplift compared to the rest of the valley.
Tributaries
All three are right tributaries and are listed in upstream order:
