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One of the most dangerous hazards of Lassen's May 22, 1915 eruption impacted land far from the volcano. While the explosive eruption and subsequent pyroclastic flows had severe impacts in the vicinity of Lassen Peak, over 30 miles away, farmers and ranchers were dealing with another hazard: mudflows. Now called "lahars" (an Indonesian word), volcanic mudflows usually result from melting snow and ice or severe precipitation mixing with with volcanic debris and flowing down drainages. In Lassen's case, a healthy mantle of winter snow provided the water source. Mudflows swept down three drainages (first photo), including Hat Creek, and traveled swiftly toward the inhabited Hat Creek Valley, "[covering] the countryside like a tidal wave".

Newspapers of the time described the scene:

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"Thirty-six families, nearly the whole population of Hat Creek Valley, are reported to be fleeing for their lives before the avalanche of mud and lava...Dozens of homes and the best farming and stock land of the valley lay directly in the channel of the flow." (Morning Union, Grass Valley, May 22 1915)

"Covering a total distance of thirty miles, the volcanic flood buried farms and orchards in a blanket of silt, at some places three feet in depth. Three homes were destroyed, much livestock perished and that no lives were lost probably was due to the quick action of Forest Ranger Frank Seaborn, who, at the first burst of flame from the volcano, rode down the valley ahead of the flood, warning residents." (Los Angeles Herald, May 22, 1915)

No human lives were lost, in part because the volcano's explosive activity had started the previous year, and people close to the volcano were aware of its dangers and had enough time to evacuate. However, those who were impacted later appealed to state and local legislators for assistance in re-establishing the flow of Hat Creek (their primary water source) and saving their crops. The mudflow buried the springs which fed the creek and destroyed its established channel (second photo), making it unsuitable for irrigation and drinking.

Thanks to Benjamin Franklin Loomis, who took these photos, and the newspapers of the time, we have a good idea what might happen in a future eruption at a snow-clad Lassen. In fact, some USGS scientists have created lahar models to show what just such a scenario would do nowadays! Check out "Lahar Hazard Zones for Eruption-Generated Lahars in the Lassen Volcanic Center, California" to see what they discovered.

Photos by B.F. Loomis, courtesy of NPS.