Late on the evening of May 19, 1915, a large steam explosion shattered the lava that had filled Lassen Peak’s crater in previous days, sending glowing blocks of hot lava onto the summit and snow-covered upper flanks of the volcano. Their impact triggered an avalanche of snow and lava rocks a half-mile wide that roared down the flank, continued over Emigrant Pass, and, as the lava blocks broke into fragments and melted the snow, turned into a mudflow and volcanic debris called a lahar. Though less forceful, the torrent followed the avalanche’s path, was deflected by Emigrant Pass into Lost Creek, and swept through homesteads. Elmer Sorahan narrowly escaped the flood and ran three miles to warn others, and although six homesteads were destroyed, no lives were lost. On May 22, 1915, lava again welled up in the crater after the May 19 eruption, pressure built, and the volcano erupted with even greater force, hurling rock fragments and pumice high into the air. A huge column of volcanic ash and gas rose more than 30,000 feet and was visible 150 miles away. Falling pumice set off another avalanche, a pyroclastic flow of hot ash, pumice, rock fragments, and gas, which rapidly gathered and melted snow, became a highly liquid lahar, followed the path of the May 19 lahar or mudflow, and rushed miles down Lost Creek, sending volumes of water into lower Hat Creek Valley again.