Some time during these eruptions, hot volcanic bombs and rock fragments were thrown out of Mount Rainier’s crater and fell onto surrounding areas of snow and ice. Wholesale melting resulted, and floods descended the east flank of the volcano carrying millions of tons of ash, newly erupted rock debris, and breadcrust bombs. Breadcrust bombs seem to be solid rock, but if you would break one open, you would find that the inside is hollow or is filled with a spongy mass of black glass. Their outer surfaces are cracked like the crust of a loaf of hard-crusted bread (fig. 9), so we call them breadcrust bombs. They originated as blobs of soft, red-hot lava which were thrown out of the volcano’s crater. As the masses arched through the air, they quickly chilled on the outside, and a hardened skin formed around the still hot and plastic core. As their outsides cooled, gas pressure in their hot interiors caused the bombs to expand slightly and their solidified outer skin to crack. When they struck the ground, many of the bombs became flattened on one side, but they were still plastic and sticky enough to remain whole. Bombs can be found in two deposits that form the south bank of the White River about half a mile downstream from the White River campground. The deposits are mudflows caused by the mixing of hot rock debris with the water from melted snow and ice. As the mudflows moved down the valley floor they must have resembled flowing masses of wet concrete. Mount Rainier erupted several times between about 2,500 and 2,000 years ago. During one of the first eruptions, a mass of hot ash, rock fragments, and breadcrust bombs avalanched down the side of the volcano and buried the floor of the South Puyallup River valley. Although this hot mass flowed like a wet mudflow, the temperature of the rock debris was above 600°F. Thus, if any water had been present, it would have been in the form of steam. You can see the resulting deposit in cuts along the West Side Road on both sides of the bridge across the South Puyallup River. Innumerable bombs have rolled from the cuts into the ditches beside the road. A charcoal log found in the deposit had a radiocarbon age of about 2,500 years. [Illustration: A large breadcrust bomb enclosed in a mudflow deposit that consists of a mixture of volcanic ash and rock fragments. The outcrop is on the south bank of the White River about half a mile downstream from the White River campground. (Fig. 9)]