A melt-water stream generally deposits coarse material wherever the slope of the valley floor decreases and the stream loses some of its velocity and carrying power. Only a flood may move the boulders farther downstream. However, the current carries fine material far downstream to deposit it in lakes, in Puget Sound, or in the Pacific Ocean. The Puyallup River, for example, is still very muddy where it enters Puget Sound at Tacoma, more than 40 miles from its source in the glaciers on Mount Rainier. During the last glaciation, when glaciers were much larger than they are now, melt-water streams carrying great quantities of sand and gravel built valley floors up to levels tens of feet higher than they are today. Later, as the glaciers grew smaller, the rivers cut down into their valley floors and remnants of the sand and gravel deposits were left standing in benches or terraces along the sides of the valleys. You can see a good example of such a terrace in the Nisqually River valley beyond Ashford, which is 5 miles west of the park. You cross it on the highway that leads to the park. Cuts beneath the terrace reveal deposits of sand, cobbles, and boulders that look the same as those deposits being formed today by melt-water streams. The terrace west of Ashford was formed a little more than 15,000 years ago, when a glacier extended down the Nisqually River valley to the vicinity of Ashford. Yesterday’s Glaciers Mount Rainier’s great sprawling cone would seem incomplete without the glistening sheets of ice that descend its flanks. We have reason to believe that the volcano has borne glaciers ever since its origin—sometimes smaller than now, at other times vastly larger. Mount Rainier probably started to grow during the middle part of the Pleistocene Epoch, or Ice Age, which began more than 1 million years ago, but glaciers had covered this part of the mountains even before the volcano appeared. Masses of rock debris formed by ancient glaciers occur beneath lava flows from Mount Rainier on the west side of Mazama Ridge just upslope from Narada Falls, on the north side of Glacier Basin, and at a few other places in the park.