Lake Helen is a crystal-clear blue glacial lake sitting just below Lassen Peak (10,463 feet) in Lassen Volcanic National Park. There is no official boat ramp into Lake Helen, but the road is only a stone's throw away, so the portage to the lake is very short. Once on the lake paddlers will notice that looking down reveals deep blue water that seemingly descends forever. Most visitors refrain from swimming in Lake Helen because it is entirely created and fed by snow melt from nearby peaks. But some people still brave the cold, especially after a hike to adjacent Bumpass Hell.
Presently Lake Helen lies to the southeast of Lassen Peak, but in years past this lake was likely nonexistent, as Mount Tehama sat in its place. This massive stratovolcano was the predecessor to the current Lassen Peak. About 600,000 years ago the volcano underwent a series of eruptions and began to collapse, leaving behind traces of its existence. Sulphur Works is thought to be the remnant of the volcano's main thermal vent, and Mount Lassen was formed from a secondary thermal vent that developed after the eventual collapse of Mount Tehama.