Bumpass Pass Boardwalk and Creek Lassen Volcanic National Park

When you reach the end of the Bumpass Hell trail at Lassen Volcanic National Park (just a short walk after you get a glimpse of the hydrothermal activity at Bumpass Hell), you reach the Bumpass Hell boardwalk. Just to the right of the boardwalk, you’ll also see Bumpass Hell creek where all the water that is part of the hydrothermal activity drains out of Bumpass Hell:

the boardwalk at Bumpass Hell with Bumpass Hell creek

Bumpass Hell creek at Lassen National Park

The Bumpass Pass boardwalk allows you to get a much better view of all the different types of hydrothermal activity taking place and it has a nice variety of information signs to explain exactly what hydrothermal activities are going on:

information sign at Bumpass Hell boardwalk

Molten rock — magma — lies miles below your feet. The magma that is chambered there is the same that fed the eruptions of Lassen Peak and other dacite-dome volcanoes like Bumpass Mountain. The magma superheats a reservoir of groundwater deep within the Earth. Steam, as hot a 464 degrees Fahrenheit (240 degrees Celsius), rises and condenses into water again, mixing with the percolating groundwater nearer the surface. The mixture produces sulfate water that escapes through park hydrothermal features at temperatures about 200 degrees Fahrenheit (93 degrees Celsius)

Bumpass Hell is the largest “escape valve” for the underground boiler or hydrothermal system and is the main upward vent. Lesser upward flows exit as Sulfur Works, Devil’s Kitchen, Boiling Springs Lake and Little Hot Springs Valley. One Furnace, One System

Bumpass Hell Lassen Volcanic National Park

The reward for hiking the Bumpass Hell trail at Lassen Volcanic National Park is reaching Bumpass Hell. If you enjoy hydrothermal activity, you will definitely enjoy the mudpots and fumaroles that Bumpass Hell has to offer. As you come off the Bumpass Hell trail, you round a corner and get a grand view of the hydrothermal activity and a beautuful turqoise pool as your first glimpse of what is to come:

Bumpass Hell at Lassen National Park

Turquoise blue pond at Bumpass Hell Lassen National Park

You also get the first whiffs of the sulfur “rotten-egg” smell that is so familiar with hydrothermal activity:

The lava rock that once filled this area has been eaten away and altered into clay by sulfuric acid. The acid can be linked to a high temperature form of sulfur (sulfur dioxide) released from the magma body that fires Bumpass Hell. The rotten-egg smell that fills the air can also be linked to sulfur. It is hydrogen sulfide gas, a forerunner to the formation of sulfur — yellow, pyramid-shaped crystals that form on the ground here.

From the first look at Bumpass Hell, it is a short walk down to the Bumpass Hell boardwalk which allows you to see all the different types of hydrothermal activity taking place at Bumpass Hell.