On the rise to the left of the trail, the parallel markings in the rock is known as flow banding and takes place when the lava is still moving but cooling rapidly. Directly above this banding, on top of the rock formation, is glacial polish, which indicates that the lava cooled long before the Ice Age.
In climbing the Peak, the trail leaves the Hudsonian Life Zone with mountain hemlocks and white-bark pine, and at timber line it enters the Arctic-Alpine Life Zone.
From near the register box atop Lassen Peak, Mt. Shasta is to the northwest, 75 miles away, looming up 14,161 feet. To the north, are Chaos Crags, the Devastated Area, Prospect Peak, Cinder Cone, and Butte Lake. Mt. Harkness, Warner Valley, and the mountains of Nevada are to the east, with Dyer Peak and Lake Almanor in the distance and Kings Creek Meadow nearby. To the southeast are the High Sierra including Pyramid Peak in the vicinity of Lake Tahoe.
To the west is the rough black dacite lava of 1915 which filled and obliterated Lassen’s 1914 Crater. This lava also spilled through the northeast notch, causing the Great Mudflow of May 19, 1915. Just beyond the 1915 lava is the 1915-1916 crater formed by the great explosive eruption of May 22, 1915. It now contains a tiny lake, sapphire blue when not frozen over. The notch on Lassen’s western skyline, just beyond, is the 1917 crater. There are active steam vents in the west and north portions of this basin, but the steam does not always condense well enough to be seen easily. There are yellow deposits of sulphur on the north wall of 1915-1916 crater.
On the west side of the crater basin, the 1915-1916 and the 1917 craters can be seen, and also the Brokeoff-Lassen Ridge to the south, glaciated Blue Lake Canyon to the southwest, Loomis Peak and the Sacramento Valley to the west, with the Coast Range Mountains beyond. The highest Coast Ranges to the northwest are the Trinity Alps. Nearby is Manzanita Lake area with Chaos Jumbles and Chaos Crags to the right (north).
Lassen Peak was named after Peter Lassen, a pioneer of Danish birth who is reported to have used the mountain as a landmark. Lassen blazed a round-about emigrant trail from Black Rock (Nevada), east and south of the present park area, to his Deer Creek Rancho “Bosquejo” in the Sacramento Valley.
(0.2 mile)
23 SUMMIT SIGN, HIGHEST POINT on the road: 8,512 feet above sea level.
For about a mile either way along the road in spring and early summer cross country skiing is normally good. Snow generally closes the road for the winter in November and plows cut through the winter pack anywhere from the end of May to early July.
(0.4 mile)