- Geology of the Snoqualmie Batholith (washingtonminerals.com)
Snoqualmie Batholith - late Oligocene to early Miocene (28 Ma[million years ago] to 22 Ma). Uplift and erosion of the Old Cascade Volcanic Arc exposed plutonic rock of the Snoqualmie Batholith near Snoqualmie Pass between Interstate 90 and State Highway 2. The batholith consists of at least eight intrusive phases, emplaced at a depth of about 4,000 and 8,000 feet. Intrusive rock types found within the Snoqualmie Batholith range in composition from granite to gabbro. Granodiorite is the most prevalent rock type, making up about 80 percent the batholith (Erikson, 1969). Other lithologies within the batholith include porphyritic dacite, andesite, aplite, and intrusive breccia (Livingston, 1971).
- Sol Duc River (Wikipedia)
The Sol Duc River (also spelled Soleduck) is a river in the U.S. state of Washington. About 78 miles (126 km) long, it flows west through the northwest part of the Olympic Peninsula, from the Olympic Mountains of Olympic National Park and Olympic National Forest, then through the broad Sol Duc Valley. Near the Pacific Ocean the Sol Duc River joins the Bogachiel River, forming the Quillayute River, which flows about 4 miles (6.4 km) to the Pacific Ocean at La Push. Although the Quillayute River is short, its large tributary rivers—the Sol Duc, Bogachiel, Calawah, and Dickey Rivers—drain the largest watershed of the northern Olympic Peninsula, 629 square miles (1,630 km2). The Sol Duc’s watershed is the largest of the Quillayute’s tributaries, at 219 square miles (570 km2).