---
source: https://iinventedlight.com/library/notes/volcano-basics.md
title: "What is a volcano, and what kinds are there?"
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, About Volcanoes, US government work, public domain; USGS, Volcanoes: Principal Types of Volcanoes, 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: "science-explain: earth and ocean science"
tags: science, geology, volcanoes
sources:
  - id: S1
    title: "About Volcanoes"
    publisher: USGS
    url: https://www.usgs.gov/programs/VHP/about-volcanoes
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Volcanoes: Principal Types of Volcanoes"
    publisher: USGS
    url: https://pubs.usgs.gov/gip/volc/types.html
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# What is a volcano, and what kinds are there?

## Short answer
A volcano is an opening, or vent, where lava, tephra (small rocks) and steam erupt onto Earth's surface. Magma rises because it is lighter than the solid rock around it. Geologists group volcanoes into four main kinds: cinder cones, composite volcanoes, shield volcanoes and lava domes. [S1][S2]

## Key points
- Eruptions can last days, months or even years. [S1]
- Cinder cones are the simplest type, built from bits of lava thrown from a single vent. [S2]
- Many of Earth's grandest mountains, such as Mount Fuji, are composite volcanoes. [S2]

## Claims
- id: C1
  claim: Volcanoes are vents where lava, tephra and steam erupt.
  source: S1
  evidence: "Volcanoes are openings, or vents where lava, tephra (small rocks), and steam erupt"
- id: C2
  claim: Eruptions can last days, months, or years.
  source: S1
  evidence: "Volcanic eruptions can last days, months, or even years."
- id: C3
  claim: Volcanoes are grouped into four main kinds.
  source: S2
  evidence: "Geologists generally group volcanoes into four main kinds--cinder cones,"
- id: C4
  claim: Cinder cones are the simplest type of volcano.
  source: S2
  evidence: "Cinder cones are the simplest type of volcano."

## Sources
- [S1] About Volcanoes. USGS. https://www.usgs.gov/programs/VHP/about-volcanoes . License: US government work, public domain. Accessed 2026-11-04.
- [S2] Volcanoes: Principal Types of Volcanoes. USGS. https://pubs.usgs.gov/gip/volc/types.html . 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).