A violent eruption of pumice and ash was followed by glassy lava oozing from the ground. From deep hot regions, magma accumulated in a chamber 2 to 4 miles below the surface at about 1600 degrees F, with overlying rock trapping water and gases in it. Fingers of magma searched for weak places underground, and when one found a path to the surface, the magma began escaping. As it rose, trapped water and gases formed billions of bubbles, and the highly gas-charged magma erupted explosively, blasting pumice and ash from the vent at tremendous speed and sweeping away forested areas in Newberry Crater, leaving gray plains of ash and pumice. Halfway through, the magma reaching the surface held much less gas, and the violent phase gave way to a passive one as a mixture of stiff, sticky liquid and froth oozed out and built a great dome over the vent. The lava then moved slowly, only inches per hour, as a 100-foot wall advanced like a glacier over the land, burying shallow valleys and low ridges because its high silica content made it flow poorly. Near the top of the flow, the lava developed at least three layers of white pumice, obsidian, and gray pumice, with the pumice layers forming where the flow frothed and foamed. In the gray pumice beneath the obsidian, gases formed giant bubbles up to 50 feet in diameter that floated upward and exploded. At the lower end of the flow, the pumice and obsidian layers became wildly contorted as the flow thickened, folding, refolding, shattering, shearing, and flowing up and over themselves while pumice tried to float, obsidian tried to sink, and great pressure ridges rose like wrinkles on a rumpled rug.