Lassen Peak, Hat Lake Reflection

Here is an early morning dual view of Lassen Peak. The peak is one of the world's largest plug domes. About 11,000 years ago, Lassen Peak forced its way up over a span of years, much like the plug dome currently building within Mount St. Helens. The plug dome is a small portion of the remains of a much larger volcano, Mount Tehama.

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Lassen Peak and 10-Foot Volcanic Block

On May 19, 1915, dacite lava from the summit of Lassen Peak cascaded down its east flank. Mixing with melting snow, a mudflow known as a lahar avalanched down and cut an 18-mile (29-Km) long swath through the forest. Giant blocks of the lava like this one were still steaming hot when witnesses dared to enter this area just days later. The site that was left barren by the lahar, and is slowly recovering, is referred to as the Devastated Area.

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West Pyrite Pool, Bumpass Hell Trail

A relatively easy 1.5-mile hike on the south side of Lassen Peak leads to this center of geothermal activity. Amidst steam vents and boiling mudpots, the Pyrite (iron sulfide - Fe₂S) Pool is formed as sulfuric acid gradually corrodes and bleaches the volcanic rocks. The sulfuric acid is formed with the help of the bacteria Sulfolobus that converts sulfur to sulfate. The sulfate then combines with hydrogen to form hydrogen sulfide (sulfuric acid).

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Lassen Peak, Evidence of Glaciation

With Lassen Peak looming in back, the evidence of Pleistocene-age glaciation in this view includes the large boulder (called a glacial erratic) on the right, and the grooves (called glacial striations) and polished surface on the left. The erratic was carried by a glacier and laid down after the glacier receded. The polished, striated surface was formed as a glacier carrying boulders like the one on the right gouged the bedrock as they moved over it.

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Lassen Peak Crater

The view north from the top of Lassen Peak looks over the craters formed during the 1914-1917 eruption. In the distance is Mount Shasta.

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Frozen Helen Lake, Lassen Peak

This is a view looking north at Lassen Peak. This was taken in July of 1999, following a winter and spring of well-above normal snowfall in the northwest.

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Lenticular Cloud from Lassen Peak

This was taken from the Lassen Peak Trail, looking southeast, away from the mountain. This lenticular cloud formed on the lee side of the mountain as high winds whipped over the top of the peak.

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Cinder Cone

The Cinder Cone is about 10 miles (16 Km) east-northeast of Lassen Peak in Lassen Volcanic National Park. It is about 700 feet (330 meters) high. A steep foot trail leads to the top of the cone, which is composed of cinders of scoriaceous basalt. Studies by the U.S. Geological Survey have established that the Cinder Cone formed in eruptions around the year 1650!

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Painted Dunes and Lassen Peak

From the southern flank of the Cinder Cone, this is the view southwest, over the Painted Dunes, toward Lassen Peak. There were actually two cinder cones, one of which was all but destroyed as the subsequent lava flows (the Fantastic Lava Beds) breached the side and rafted the cinders off with it. The Painted Dunes are composed of oxidized cinders lying over the Fantastic Lava Beds. In the distance, the concave flank (right side) of Lassen Peak is where the lahar blew down the peak in 1915 to create the Devastated Area.

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Fantastic Lava Beds Close Up

Along the trail that follows the western edge of the lava flow, the steep side and height of the lava flow is more apparent. This is aa-type basalt, with blocks of oxidized cinders that probably rafted off of the Cinder Cone as the lava flow breached the side of the cone.

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Lava Dam at Snag Lake

The southern end of the Fantastic Lava Bed flow extends into the northern end of Snag Lake. This is one of two volcanic dams created by these lava flows. The other lies 2.5 miles (4 Km) to the northeast at Butte Lake. The abrupt, steep front of the aa lava flow is reminiscent of some of the Kilauea, Hawai'i flows that are slow and gradually-consuming.

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