South Cascade Glacier is a large alpine glacier in the North Cascades of Washington, USA. It is bordered on the east by 8,261-foot Sentinel Peak, and is about 17 mi north of Glacier Peak in the Glacier Peak Wilderness. Meltwater from the glacier flows directly into South Cascade Lake, which feeds the South Fork Cascade River, which is a tributary of the Skagiā¦South Cascade Glacier is a large alpine glacier in the North Cascades of Washington, USA. It is bordered on the east by 8,261-foot Sentinel Peak, and is about 17 mi north of Glacier Peak in the Glacier Peak Wilderness. Meltwater from the glacier flows directly into South Cascade Lake, which feeds the South Fork Cascade River, which is a tributary of the Skagit River.