Beginnings of a controversy After traveling through Northern California in the spring of 1851, two
gold prospectors reported seeing an erupting volcano that "threw up fire to a terrible height" Cinder Cone's name was officially recognized by the
United States Board on Geographic Names in 1927. In the mid-1930s, USGS volcanologist
R. H. Finch attempted to improve on Diller's work. On the basis of other studies done at Cinder Cone, Finch thought (1) that there had been at least five separate lava-flow events, as suggested by crude, experimental magnetic measurements; (2) that the youngest lava flow was extruded in 1851, accepting Harkness' (1875) historical "evidence" and ignoring Diller's interviews and conclusions; and (3) that there had been at least two distinct explosive eruptions of the cone. Using these assumptions and tree-ring measurements, Finch proposed a complex and detailed eruptive chronology for Cinder Cone that spanned nearly 300 years. From measurements of the rings of one particular tree, which showed two periods of slow growth, he thought that the two explosive eruptions occurred in 1567 and 1666. He also concluded that the five lava flows were extruded in 1567, 1666, 1720, 1785, and 1851.
New geologic studies After Finch published his work in 1937, few additional studies were done on volcanic hazards in the Lassen area. However, that changed after the
1980 eruption of Mount St. Helens in
Washington. As a result, the USGS began reevaluating the risks posed by other potentially active volcanoes in the Cascade Range, including those in Lassen Volcanic National Park. Since that time, USGS scientists have been working in cooperation with the National Park Service to better understand volcanic hazards in the Lassen area. As part of this work, the history of Cinder Cone has been reexamined. Most of the features of Cinder Cone have changed little since Harkness first described them in the 1870s, but all of the assumptions on which Finch based his conclusions have now been shown to be incorrect. Through new field and laboratory work and by reinterpreting data from previous studies, USGS scientists have shown that the entire eruptive sequence at Cinder Cone represents a single continuous event. Because the orientation of the Earth's magnetic field in northern California during the 1850s is well known and is different from the remnant magnetizations at Cinder Cone, the lava flows there could not have been erupted in 1850 or 1852. Also, there are no discernible differences in the magnetic orientation recorded by any of the Cinder Cone lava flows, and so the flows had to be extruded during an interval of less than 50 years. Although paleomagnetic evidence can be used to rule out the 1850s as the age of Cinder Cone, it does not provide an actual age for its eruption. By measuring levels of
carbon-14 in samples of wood from trees killed by the eruption of Cinder Cone, USGS scientists obtained a radiocarbon date for the eruption of between 1630 and 1670. Such a date is also consistent with the remnant magnetization preserved in the lava flows. The series of eruptions that produced the volcanic deposits at Cinder Cone were complex and are by no means completely understood. However, the new studies done by USGS scientists refute the purported accounts of an eruption in the early 1850s and confirm Diller's (1891, 1893) interpretation that Cinder Cone erupted in the latter half of the 17th century. They also suggest that the 1666 tree-ring date proposed by Finch (1937) for his "second" explosive eruption at Cinder Cone might actually date the entire eruptive sequence. ==See also==