The pumice deposits here were produced by Mt. Mazama, an explosive volcano that collapsed to form the Crater Lake caldera. Mazama stood about 6 miles south of here. About 7,700 years ago, Mt. Mazama erupted torrents of seething, red-hot pumice and other volcanic rocks. These glowing avalanches raced down the slopes and flooded the valley here with deposits over 100 feet deep. Even after thousands of years, few trees have become established on the Pumice Desert. There is ample water under the surface, but deficiencies in the soil limit plant growth. Many more years will pass before the surrounding lodgepole pines transform the desert to a forest. Avalanches of heated rocks ejected by Mt. Mazama flooded downhill. Mostly pumice and scoria, the porous rocks discharged gasses that buoyed up the flow. Some rocks travelled up to 25 miles beyond this point.