Big Muddy River The Big Muddy was not covered by the Wisconsin Glacier, about 70,000 to 10,000 years before present. However, during the melting of that glacier, the level of the Mississippi River was much higher. Water backed up into the Big Muddy Basin, forming a lake much like the artificial Rend Lake but covering a larger area. The ancient lake silted in, forming a flat bottom. After the melting of the Wisconsinan glacier, the level of the Mississippi dropped, allowing the lake to drain. A new channel formed within the old lake bed. This channel meandered in the flat bottom of the
Muddy River (Washington) 83 and passes the Ape Canyon Trailhead and the Lava Canyon Interpretive Site, both on the left, before entering Muddy River Gorge. Flowing northeast through the gorge, the stream plunges over three waterfalls before emerging from the narrows and curving sharply again to the southeast. Here Crane Lake is on the left, Smith Creek enters from the left, and Smith Creek Trailhead is on the right. Slightly downstream of the trailhead, the river leaves the national volcanic monument but remains in the national forest. At about the level, Clearwater Creek enters from the left. Turning south, the river descends less