were there any explorers who carried out a research on it?
Yes,  Lassen Peak's first recorded ascent took place in 1851, led by Grover K. Godfrey
Lassen Peak
Lassen Peak's first recorded ascent took place in 1851, led by Grover K. Godfrey. 
when was the last time a volcano erupted in california During the 20th century what is lassen peak? It is commonly referred to as Mount Lassen, is the southernmost active volcano in the Cascade Range of the Western United States
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Lassen Peak [SEP] Human history
This trail was replaced by the Nobles Emigrant Trail, named for the guide William Nobles, who pioneered the trail in 1851. Lassen Peak's first recorded ascent took place in 1851, led by Grover K. Godfrey. In 1864, Helen Tanner Brodt became the first woman to reach the summit of Lassen Peak, wanting to sketch the surrounding landscape. A tarn lake on Lassen Peak is named "Lake Helen" in her honor. The Bumpass Hell, a hydrothermal vent area near Lassen Peak, was named after a pioneer who suffered burns there and lost his leg shortly after. Other historic names for Lassen Peak include Mount Joseph (from 1827), Snow Butte, Sister Buttes, and Mount Lassen.