It was the late-afternoon of May 22, 1915 when Lassen Peak exploded in a powerful eruption that blasted rock fragments and pumice high into the air and sent a column of gas and volcanic ash 30,000 feet into the air.
Lassen first showed signs of coming to life on May 30th, 1914 with steam explosions near the summit. These continued for almost a year, more than 180 releases in all, expanding the summit crater by 1,000 feet. On the evening of May 15th, 1915, the first lava was sighted spilling down the flanks of the volcano and filling in the summit crater. A few days later on May 19th another explosion created a new summit crater. There was still 30 feet of snow at the summit, and the hot rocks created a half-mile-wide avalanche that spilled down the side of the volcano and into Hat Creek four miles away.
“From the crater and crevasse were coming puffs of steam and ashes,” reported park ranger Harvey Abbey. “Noises coming from the crater were heard that sounded like something dropping down in the bottom of the crater….Along the sides of the crater were small, round holes, where the steam was gushing out.”
As the snow in the avalanche melted it mixed with volcanic materials to form a mudflow called a lahar. This then raced down Lost Creek canyon for another seven miles. Hat Creek Valley was flooded with muddy water on May 20th, which damaged several ranches in the Old Station area. Floodwaters headed down Hat Creek to the Pit River, over 30 miles, and witnesses claimed the muddy waters killed many fish. Of course, there were salmon and steelhead in all these waters back then. More lava spilled from the summit on the 19th and 20th reaching down the mountainous flank another 1,000 feet.
The next powerful explosion happened around 4:00pm on May 22nd blowing rocks high into the air above the summit. Shortly thereafter a column of volcanic ash and gas rose some 30,000 feet above the mountain, which was visible from 150 miles away. A pyroclastic flow, an angry burst of hot gas and rock blasted down Lassen’s flank at up to 450 miles per hour and 1,000 degrees clearing three square miles of virtually everything in its path.
Another mudflow (lahar) was generated by the pyroclastic flow that again blew 15 miles down Lost Creek and releasing another blast of muddy water down Hat Creek. Volcanic ash flowed down the mountain and fine volcanic ash blew in a northeasterly direction as far away as Elko, Nevada. Smaller eruptions continued between 1914 and 1917, and steam continued to leak from the calming volcano well into the 1920s.
Following the eruption of Lassen Peak from 1914 to 1917, the volcano went from looking like this:
To looking like this:
Today the science of volcanic eruption prediction is far more advanced than it was in the dawn of the 1900s, but it is far from foolproof either. Most volcanoes “announce” their pending activity as long as years in advance to only a matter of days. Fortunately the prevailing winds typically blow from West to East in NorCal, so volcanic ash from another eruption would most likely be blown away from major population centers along the I-5 corridor.
This, however, is no reason to get too comfortable. There are too many ways future eruptions could cause catastrophic problems for North State residents and visitors, not to mention traffic on I-5 and even airline routes worldwide.