Field Trips

Bumpass Hell - Exploration of an Active Hydrothermal Area

Grade Level:
High School: Ninth Grade through Twelfth Grade
State Standards:
California NGSS
MS - ESS3-1
HS - ESS2-1


Students will visit an active hydrothermal area in Lassen Volcanic National Park to identify the main features and learn about the chemical processes forming these areas. This activity was designed to have students interact with the natural resources found along the trail. Students need to think about the natural phenomena they are observing and try to make sense of it. Discussion post- field trip will tie all the information together. Based on an original work from the Lassen Volcanic National Park Activity Guide for Teachers, developed by the National Park Service as part of the “Parks in the Classroom” initiative. This field trip adaptation was written by Tom George, high school Earth Science teacher.


To introduce students to the features and processes that have shaped and reshaped Lassen Volcanic National Park’s hydrothermal area.


  • Identify and describe three common hydrothermal features.
  • Name at least five colors found at the hydrothermal features and a key to identify the processes which created them.
  • Explain two important safety rules for enjoying and learning while in hydrothermal areas.
  • Explain how hydrothermal areas are formed and continue being active.

Time Required

From the parking lot to Bumpass Hell and return, allow 3 hours.


Bumpass Hell hydrothermal area of Lassen Volcanic National Park.


  • Hydrothermal Area Field Trip Guide – one for each student
  • Writing instrument – pencil or pen
  • Pair of binoculars for each group of students. 1 pair for every 2 students is ideal.
  • At-a distance/non-contact thermometer – one per group


  • Volcano: A vent in the earth’s surface that allows magma and gases to come out of the earth’s interior.
  • Hydrothermal: Hot water heated by the earth.
  • Magma: Molten rock formed in the earth.
  • Lava: Molten rock outside of the earth on the surface.
  • Fumarole: A hydrothermal vent where gases are released.
  • Mud pot: A hot spring filled with bubbling or boiling mud.
  • Hot Spring: A thermal spring of water that is hotter than the human body (>98°F).


The fumaroles, boiling springs, and mud pots in the park’s hydrothermal areas testify to the landscape’s volcanic origin. Rain and melted snow percolate deep into the earth, where the water is heated by a mass of hot rocks. The rocks are heated by magma barely 3 miles below the surface.  The water underground is pressurized, and that elevates the boiling point of the water. Steam as hot as 464°F rises and condenses into water again, mixing with percolating ground water nearer the surface. This mixing produces sulfate water that boils at elevated pressure at about 200°F. All the park’s hydrothermal areas are interconnected and fed by the same hydrothermal reservoir underground. Features such as fumaroles, mud pots, and boiling springs congregate in the same areas and change behavior because of differing water amounts in the underground reservoir.

Instruction Sequence


Frontload behavior expectations before leaving for the park.

  • This is everyone’s park, and everyone is encouraged to visit. It was started for the benefit and enjoyment of all the people and so there are rules about how to respect the park and its places.
  • Throwing rocks, sticks, trash, or anything else into the boiling springs, mud pots, or fumaroles is not allowed.
  • In national parks, all natural and cultural features are protected by law.
  • Always stay on the trail and boardwalks.
  • Do not touch the water or other features in the hydrothermal area. They may be hot and/or contain strongly acidic chemicals. Breaking the rules could result in severe burns or other personal injuries.

Share the story of Kendall V. Bumpass

Bumpass Hell is named after Kendall V. Bumpass, the first person of European descent to know this hydrothermal area. Bumpass “walked off the trail” and fell through some thin crust ground, burning his foot. He returned, sometime later, with a newspaper reporter on a tour of this area. Bumpass broke through the thin ground again, in a different spot, and plunged into a boiling spring. His leg was severely burned and had to be amputated.

Demonstrate use of Equipment

All students need to be familiar with the use of binoculars and non-contact thermometers.

At the Trailhead

  • At the parking area, make sure all the students understand the rules.
  • Divide the class into small working groups of two to four students.
  • Hiking groups, including adult leaders, can be up to 20 people.
  • Tell the class they are going to be studying the largest accessible hydrothermal area in the park.
  • Pass out the Hydrothermal Area Field Trip Guide activity page. Read and review what the students will do out on the trail and boardwalk. Each group is to record their observations on the field trip guide.
  • Distribute binoculars and non-contact thermometers.
  • Students are to hike the Bumpass Hell trail, carrying their field trip guide with a pencil and some data gathering devices like a pair of binoculars and a non-contact thermometer.
  • Along the trail, at certain locations, students write observations or take measurements.
  • This hike activity should take about 3 hours total time.
  • Students need to have skills for
    • using binoculars in order to see far objects clearly,
    • using a non-contact thermometer, and
    • observation along the trail.
  • Set a time limit for returning to the parking lot. Groups should allow at least 30 minutes for the return hike.
  • The results of student observations will be discussed back in class.


  • Discuss and review what the class saw and experienced.
  • Make sure to emphasize what they discovered or guessed were the processes observed in the Bumpass Hell area.
  • Emphasize the reasons for the colors seen out at Bumpass Hell. Ask students what colors they would expect to see with the various chemical or biological agents at work.
    • Yellow: The yellow color and crystals are formed from sulfur dioxide gases escaping into the air from a fumarole or vent. As the gas escapes, it leaves behind a deposit of pyramid-shaped sulfur crystals or stains. During the oxidation of hydrogen sulfide, sulfuric acid (H2SO4) is also produced. The rotten egg smell is hydrogen sulfide gas (H2S). The general idea is H2S(g) + O2(g) → S(s) + H2SO4(aq).
    • White: The soft, white, powdery soil is what is left of volcanic rock after it has been completely broken down by sulfuric acid and steam. The soil is made up of silica and kaolinite (clay) material. It is soft and doesn’t support much weight. That is why everyone stays off the bare soil in Bumpass Hell basin and stays on the boardwalk or trail.
    • Black or Gray: The black and gray colored soils are volcanic rock that has not yet been completely broken down by the sulfuric acid and steam. This results in gray colored clay minerals or black and brown iron mineral compounds. These minerals are splattered out and deposited on the surface near a vent. The black scum on the surface of some of the pools is iron-sulfide mineral, also known as iron pyrite or “Fool’s Gold.”
    • Red, Tan or Brown: The red, brown or tan staining is due to iron-rich mineral compounds that are dissolved in the water and steam of the boiling pools and fumaroles. These minerals were dissolved underground by the steam coming from the underground reservoir and precipitate out as solids that react with the ground.
    • Gray-Colored Water and Mud: This was once solid rock. Heat, water, volcanic gases, and sulfuric acid have chemically altered the volcanic rock and changed it into gray colored clay.
    • Yellowish-Orange: The yellow-orange material that covers the ground is sulfate mineral. Sulfate-rich water evaporates at the surface, leaving the colorful sulfate mineral deposits behind.
    • Green: The green color is a plant called alga that grows in the cooler parts of the hot springs, on rocks, in the stream, or on the edges of the hot pools. Other microorganisms including bacteria also live in the hydrothermal features. These organisms are not true bacteria and are known as Archaea.
  • Show students the chemical or biological processes that make Bumpass Hell such an intriguing place to visit.
  • Discuss results with the class.


  • Have students compare/contrast Bumpass Hell with hydrothermal features of Yellowstone National Park, which has approximately 10,000 different features.
  • Have students imagine they are newspaper reporters who have traveled to the hydrothermal area with Mr. Bumpass in 1865. Write a story about that experience.


  1. Write an explanation of why the soil in the Bumpass Hell basin is so different from the soil at the trailhead near the parking lot.
  2. Explain the smell of the air surrounding Bumpass Hell.
  3. Share your experiences at the park’s hydrothermal area with another class or your parents.
  4. Develop student questions based on the field trip guide.


R. Forrest Hopson and Michael A. Clynne. 2019. Geology of the Lassen Country: The Geologic Story of Lassen Volcanic National Park and Vicinity. Backcountry Press, Kneeland CA.


A student data sheet for recording observations during the Bumpass Hell field trip

Download Bumpass Hell Field Trip Guide - Student Observations

Last updated: June 8, 2021