---
source: https://iinventedlight.com/library/notes/yellowstone-volcano.md
title: "Yellowstone: the volcano and its observatory"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: USGS, Yellowstone, US government work, public domain; USGS, Yellowstone Volcano Observatory, US government work, public domain."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "earth science: volcanoes"
tags: ['usgs', 'yellowstone', 'volcanoes', 'geology']
sources:
  - id: S1
    title: "Yellowstone"
    publisher: USGS
    url: https://www.usgs.gov/volcanoes/yellowstone
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Yellowstone Volcano Observatory"
    publisher: USGS
    url: https://www.usgs.gov/observatories/yvo
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# Yellowstone: the volcano and its observatory

**Answer:** The Yellowstone Plateau volcanic field developed through three volcanic cycles that span two million years. Two of the eruptions are considered some of the world's largest volcanic events. Yellowstone's youngest eruptions have been lava flows that remain confined to the caldera of present-day Yellowstone National Park.

## The three cycles

- The Huckleberry Ridge Tuff erupted about 2.1 million years ago, creating an approximately 75 km (47 mi) wide caldera and thick volcanic deposits.
- A second eruption cycle concluded with the much smaller Mesa Falls Tuff around 1.3 million years ago.
- Activity then shifted to the present Yellowstone Plateau and culminated 640,000 years ago with the eruption of the Lava Creek Tuff and the formation of a 45 x 85 km (28 x 53 mi) caldera.

## Since then

USGS lists the most recent eruption as 70,000 years ago (lava). The 77,000 year-old Pitchstone Plateau flow is the volcano's most recent lava. No magmatic eruptions have occurred since then, but large hydrothermal explosions have taken place during the Holocene, including from within and near Yellowstone Lake.

## Monitoring

The Yellowstone Volcano Observatory (YVO) is a consortium of nine state and federal agencies who provide timely monitoring and hazard assessment of volcanic, hydrothermal, and earthquake activity in the Yellowstone Plateau region. The USGS arm of YVO is also responsible for monitoring volcanic activity in the intermountain west U.S. states.

Infrasound and seismic sensors identified an explosion in Norris Geyser Basin on 15 April 2024, the first instrumentally detected hydrothermal explosion in the Yellowstone region. Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the observatory.

## Claims
- id: C1
  claim: The Pitchstone Plateau flow is the volcano's most recent lava.
  source: S1
  evidence: "The 77,000 year-old Pitchstone Plateau flow is the volcano's most recent lava."
- id: C2
  claim: Two of the eruptions are among the world's largest volcanic events.
  source: S1
  evidence: "Two of the eruptions are considered some of the world's largest volcanic events."
- id: C3
  claim: Sensors detected a Norris Geyser Basin explosion on 15 April 2024.
  source: S2
  evidence: "Infrasound and seismic sensors identified an explosion in Norris Geyser Basin on 15 April 2024"

## Sources
- [S1] Yellowstone. USGS. https://www.usgs.gov/volcanoes/yellowstone . License: US government work, public domain. Accessed 2026-11-04.
- [S2] Yellowstone Volcano Observatory. USGS. https://www.usgs.gov/observatories/yvo . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).