The volcano's crater welled up again with lava following the May 19th eruption. Like a lid covering a boiling pot, the pressure built. Late on the afternoon of May 22, 1915, Lassen Peak blew again. This time it erupted with even greater force. The blast hurled rock fragments and pumice (lava filled with gas bubbles) high into the air. Ahuge column of volcanic ash and gas rose more than30,000 feet and could be ssen 150 miles distant.

The falling pumice created yet another avalanche, a pyroclastic flow of hot ash, pumice, rock fragments, and gas. The avalanche rapidly gathered and melted snow in its path, transforming into a highly liquid lahar and following the path of the May 19th lahar or mudflow. It rushed miles down Lost Creek, flushing volumns of water into lower Hat Creek Vally once again.