LASSEMHVOLCAN«C !B8& UNITED STATES Historic Events DEPARTMENT OF THE Lassen INTERIOR OPENING Harold L. Ickes, Secretary AND CLOSING Volcanic 1820 Arguello exploring party first to record DATES DEPEND and name Lassen Peak (St. Joseph's UPON NATIONAL PARK Mountain). 19 40 WEATHER CALIFORNIA CONDITIONS 1850-51 Last lava flow from Cinder Cone. LASSEN PEAK, WITH LAKE HELEN NATIONAL PARK SERVICE IN FOREGROUND Arno B. Cammerer, Director C OJ^TEU^TS 1864 Helen Brodt, first white woman to climb Lassen Peak, made ascent with Major Reading. Lake Helen named for Eruption of Lassen Peak her. 1 in 1915 Cover ASSEN VOLCANIC NA­ GEOLOGIC HISTORY TIONAL PARK, in northeast­ The Cascade Range, which is vol­ Geologic History .... 3 ern California, was created by canic in origin, is not ancient, measured 1906 May 6. Lassen Peak and Cinder Cone L Lassen Peak and Vicinity . 3 act of Congress approved August 9, in geologic time. Its beginning dates National Monuments established. 1916, to preserve Lassen Peak and the back to the Pliocene period, about a Chaos Crags and Chaos area containing spectacular volcanic ex­ million years before the great ice age Jumbles 6 hibits which surrounds it. This impres­ or glacial epoch. The present range sive peak, from which the park derives rests upon a great platform of lava Ancestral Mount Tehama . 6 1914 May 30. First known eruption of Las­ sen Peak since coming of white man. its name, stands near the southern end flows, which issued from many vents Cinder Cone Area ... 7 of the Cascade Mountains and is the and fissures. These lavas accumulated, only recently active volcano in the flow upon flow, to depths of several View from Lassen Peak . 8 United States proper. Its last eruptions, thousand feet over wide areas in Wash­ 1915 May 19 and 22. Major eruptions of occurring between 1914 and 1921, ington, Oregon, southern Idaho, and Wildlife 8 Lassen Peak devastated large forest aroused popular and scientific interest northern California. Later this platform area. Fishing 10 in the area. was bent, or arched, slightly upward Camping 10 Lassen Peak was named for Peter along the line of the Cascades. No more widespread floods of lava came Educational Activities ... 10 Lassen, an early pioneer in northern 1916 Lassen Volcanic National Park created California. He was born near Copen­ forth, but numerous localized eruptions by act of Congress. Administration 11 hagen, Denmark, in 1800, and came produced the magnificent series of peaks which are now snowcapped and How to Reach .the Park . 11 to the United States when he was thirty. After he became acquainted with for which the Cascades are famous. LASSEN PEAK AND VICINITY. — The Accommodations in the Park 13 1921 Lassen Peak ceased to erupt and sub­ northern California, he piloted emi­ western part of the park includes a What to Do and See ... 15 sided into a state of quiescence. grants from Humboldt, Nev., into the Sacramento Valley, using Lassen Peak 1 Abstracted from Gcoloxy of Lassen Volcanic Na­ as a landmark. tional Park, by Howcl Williams. 2 Lassen Volcanic Natiotial Par\ . California Lassen Volcanic National Par\ . California 3 profusion of volcanic peaks of the and slabs of rock accompanied by many "dome" type, of which Lassen Peak smaller fragments. These accumulated itself is the outstanding example. Others about the rising dome while the moun­ include White Mountain, Chaos Crags, tain was still growing and formed Eagle Peak, and Bumpas Mountain, all great rock slides on its slopes, much closely related in origin. as they appear today. This rock mantle (talus) in places reaches almost to the The great cone of Lassen Peak, ris­ summit and caps the bulging dome in ing 10,453 feet above sea level, on the the form of a cone. north slope of an ancestral mountain, is almost completely wrapped in a Compared with the slow upbuilding smooth-sloping mantle of rock frag­ of the more common type of volcano, ments, broken from its own cliffs. Las­ the rate of growth of an upswelling sen differs from the "strato-volcanoes," dome is phenomenally rapid, as wit­ the most common type, which are built nessed by the history of Santa Maria, up of alternate beds of lava and frag- in Guatemala, and Mont Pelee, in the mental material, sloping away steeply Island of Martinique. By comparison from a central crater. The mountain with the growth of these two domes it has been estimated that the steep as it stands today has passed through Lind photo cone of Lassen Peak may have been two stages of growth. The earlier Las­ ISLAND LAKE AND BONTE PEAK sen was a broad, gently sloping vol­ thrust up in a comparatively short time. cano of the "shield" type, built of layer Most dome volcanoes have no crater in the mud and recently have been upon layer of lava. flows of mud which swept 20-ton at the top, but at Lassen Peak gases uncovered along the course of Lost boulders 5 to 6 miles into the valleys It rose by a succession of lava flows escaping from lavas deep below main­ Creek. of Hat Creek and Lost Creek. tain open conduits through the softer, to an elevation above 8,500 feet, with On May 30, 1914, a series of erup­ Three days later, on May 22, another central part of the cone. The violence a base 5 miles across from north to tions began which lasted until February and lesser mud flow moved down the of their discharge at times shoots forth south and 7 miles from east to west. 1921, the most recent volcanic activity same slope, and minor flows took place lava in dustlike form, producing the In the second stage the steep Lassen in United States proper. Unfortunately, on the north and west flanks of the so-called volcanic "ash" of the tuff beds cone was built on this broad, substantial during this period no scientific observer volcano. At the same time a terrific and "mud" flows. Such activity opens platform. This, the more conspicuous was present in the region to record and hot blast, heavily charged with dust and a funnel-shaped or cuplike crater at portion, represents a still rarer "dome" report the detailed account of events. rock fragments, was discharged down type of volcano, formed by stiff, viscous the top. Before the eruptions of 1914-21 Violent eruptions occurred in May the northeast flank of the peak. So lava which was pushed up through the the crater of Lassen Peak was an oval 1915, possibly set off by the melting of violent was this outburst that trees on vent, like thick paste squeezed from bowl approximately 1,000 feet across the exceptionally heavy snow which the slopes of Raker Peak, more than a tube. Piling up in and around the and 360 feet deep. had accumulated during the preceding 3 miles away, were felled uniformly in old crater, this stiff lava rose in a Following the rise of the Lassen winter. On May 19 the first glowing the direction of the on-rushing blast. bulging domelike form high above it. Dome, there was a long period of lava made its appearance, rising in the At the same time a vertical column of Movements due to the rise of lava quiescence. Nevertheless, prior to the new crater and spilling through the smoke and ash rose more than 5 miles into the upswelling mass, the pressure activity of 1914-21 one or more "mud" western notch in the crater rim in the above Lassen crater. of steam and gases imprisoned within flows had swept down the northeastern form of a tongue which reached down The energy of the volcano was large­ it, and the chill of the outer portions slope, probably within the past 500 the slope 1,000 feet. During the night ly spent by the end of the 1915 erup­ on exposure to the air caused a con­ years, as judged from the state of of May 19 the snow was melted on the tion. With only occasional outbursts of tinuous breaking away of huge blocks preservation of logs that were buried northeastern slope, causing destructive steam and ash, the activity subsided 4 Lassen Volcanic National Park\ . California Lassen Volcanic National Part\ . California 5 during the next 2 years. A series of from various parts of the stiffening violent explosions occurred in May and mass. Thus vast talus slopes were June 1917, again following the melting formed by the breaking and crumbling of considerable quantities of snow. The of the rising masses, and the domes activity of 1916 and 1917 produced little were thrust up through their own ac­ effect besides modifying the form of the cumulating debris. crater by opening new vents within it. The north dome had risen 1,800 feet Most of the crater is now filled by the above the surrounding country when rough, blocky lava which rose into it explosions at the base of the rising in May 1915; but at the northwest a mass blasted away the support from yawning chasm through the crater wall the north face and hurled vast quanti­ was opened by later explosive erup­ ties of broken and falling lava out tions. In view of the volcanic history upon the cinder-covered region below. of the region, renewed activity at Las­ This rock blast was shot forward with sen is not probable for many years, al­ such momentum that its front advanced though there is no reason to suppose 400 feet up the opposite slope of Table that the volcano is yet extinct. Mountain, 2 miles distant from the CHAOS CRAGS AND CHAOS JUMBLES.— craters at the north foot of the Crags, Chaos Crags and Chaos Jumbles pre­ and stopped there with an abrupt front.