Podcast Summary: But Why: A Podcast for Curious Kids

Episode: When did volcanoes start existing?
Date: September 19, 2025
Host: Jane Lindholm (Vermont Public)
Guest: Professor Freystein Sigmundsson, Volcanologist, University of Iceland

Episode Overview

This episode explores kids’ burning questions about volcanoes, from their origins and eruptions to why lava glows and how scientists predict eruptions. Host Jane Lindholm interviews Professor Freystein Sigmundsson, a volcanologist from Iceland, diving into the science and wonder of these fiery geological features. The discussion is sparked by recent global volcanic activity and fueled by questions sent in from children around the world.

Key Discussion Points & Insights

1. Active Volcanoes Around the World

• Recent eruptions in Iceland, Russia, and Japan illustrate just how common volcanic activity is worldwide.
  • “At any given time there are typically 40 to 50 continuing eruptions... around 20 will be actively erupting on any particular day.” - Jane Lindholm [01:30]
• Volcanoes may seem mysterious to most people, but they're a regular part of Earth’s activity.

2. Meet the Volcanologist

• Professor Freystein Sigmundsson studies "what is inside volcanoes" at the University of Iceland.
  • “Volcanology is a very broad field. You can study the rocks on a volcano. What I try to do is to study what is inside the volcanoes.” [04:09]
• Grew up during a period of intense volcanic activity in Iceland, which inspired his career. [04:39]

3. What is a Volcano?

• “A volcano is in essence a crater that has erupted a magma. And in most cases, we would expect it to have erupted more than once. So it builds up some kind of a mountain.” - Prof. Sigmundsson [05:33]
• Magma = molten rock inside the volcano (analogy: magma is to volcano as blood is to the human body). [06:02]
• Lava = magma that reaches the surface.

4. How and Why Volcanoes Form and Erupt

• Volcanoes form where Earth's heat needs to escape, often at tectonic plate boundaries (e.g., Iceland is on the Mid Atlantic Ridge).
• Eruptions are caused by magma accumulating under pressure until it bursts through the surface, similar to blowing up a balloon until it pops.
  • “The more new liquid that flows into a volcano, the pressure increases... The eruption starts when the pressure is too much inside the balloon.” - Prof. Sigmundsson [09:45]
• Two main eruption types:
  • Effusive: Lava flows steadily, forming new land.
  • Explosive: Magma and gas explode into tiny particles, causing ash clouds and darkness. [06:51]

5. When Did Volcanoes Begin? The Origin Story

• Volcanoes have existed since the planet formed.
  • “The first volcanoes were really born when the planet was forming... We don’t have a name for the first volcano.” - Prof. Sigmundsson [07:57]
• Example: Iceland’s volcanoes began forming about 20 million years ago.

6. Underwater Volcanoes

• Submarine volcanoes are common—sometimes leading to the creation of new islands.
  • Eruptions under shallow water can be extra explosive. “The volcano rose out of the sea.” - Prof. Sigmundsson [11:29]

7. Kids’ Curiosities: Lava, Heat, and Color

• Why do volcanoes have lava? Because underground rock becomes so hot it melts, and the Earth is always trying to release this heat. [14:18]
• What is lava made of? Melted rock, containing minerals and crystals.
• Why is lava orange? “It is transmitting energy. It is so hot that it starts to radiate energy. The orange color is simply radiation from a different temperature.” - Prof. Sigmundsson [15:18]
• Volcano vs. Sun: Volcanoes reach about 1,000°C (1,800°F); the sun’s core is 15 million°C—so the sun is much, much hotter. [12:34]

8. Lava Field Dangers and Cooling

• Cooling can take years, especially in thick lava fields. Even a year after eruption, underground lava might stay dangerously hot.
  • “They can have really liquid magma inside them... for months or years.” - Prof. Sigmundsson [16:46]
• Surfaces are irregular—risk of falling is another danger.

9. Why Live Near Volcanoes?

• Many people do!
  • “Lots of people live on volcanoes... In Indonesia, the soil can be very fertile.” - Prof. Sigmundsson [17:38]
• In Iceland, geothermal heat from volcanoes provides energy for most homes. [18:21]
• Most volcanoes are dormant for hundreds or thousands of years—living nearby is sometimes perfectly safe, but eruptions are unpredictable.

10. Predicting Eruptions

• Forecasting is challenging, like predicting when you'll throw up if you’re sick.
  • “If you have a stomach disease... you almost throw up, but then suddenly it comes... The same is with volcanoes. It is difficult to forecast when they throw up.” - Prof. Sigmundsson [18:57]
• Scientists use three main techniques:
  1. Monitoring earthquakes in the volcano
  2. Measuring ground movement
  3. Watching volcanic gases [20:34]
• Visual signs sometimes include increased steam, but technical tools and computer models are crucial.

11. Volcanoes: Not Just Scary, But Beautiful and Essential

• Though destructive, volcanoes also create new land, fertile soil, and energy sources.
  • “If you look at some photographs or videos of volcanoes, it's a beautiful thing to see a small eruption... They are beautiful, spectacular” - Prof. Sigmundsson [24:45]

Notable Quotes & Memorable Moments

• On volcano formation:
  “The existence and evolution of our planet is all about volcanoes.” - Prof. Sigmundsson [07:57]

• On predicting eruptions:
  “Volcanoes are not like clock.” - Prof. Sigmundsson [20:17]

• On lava color:
  “The orange color is simply radiation from a different temperature.” - Prof. Sigmundsson [15:18]

• On living near volcanoes:
  "We heat most of the houses in Iceland by water that comes from the volcanoes, hot water, and it just goes into a radiator directly from volcano and heats our houses." - Prof. Sigmundsson [18:21]

• On volcano beauty:
  "They are beautiful, spectacular, and if you stare at them for a long time, stare into the red glow, you can be charmed." - Prof. Sigmundsson [24:45]

• On volcano lifespans:
  "A volcano here in Iceland is about half a million years. So mankind, we are very small in comparison to the lifetime of volcanoes." - Prof. Sigmundsson [07:57]

Timestamps for Key Segments

• [01:30] Overview: How frequent are volcanic eruptions worldwide?
• [04:07] Meet Professor Freystein Sigmundsson
• [05:33] What is a volcano and how does it form?
• [06:51] Types of eruptions
• [07:57] When did the first volcanoes form?
• [09:45] Why and how do volcanoes erupt?
• [11:29] Underwater volcanoes
• [12:34] Which is hotter: the sun or a volcano?
• [14:18] Where does lava come from and what is it made of?
• [15:18] Why is lava orange?
• [16:46] How long do lava fields stay hot and dangerous?
• [17:38] Why do people live near volcanoes?
• [18:57] Eruption prediction: “volcanoes throwing up” analogy
• [20:34] How to monitor volcanoes for signs of eruption
• [24:45] On the beauty and importance of volcanoes

Tone and Language

Throughout the episode, the discussion stays engaging, clear, and accessible for kids, with Professor Sigmundsson often using analogies (volcanoes as balloons or people “throwing up”) and drawing on real experiences from Iceland. The host maintains a warm, curious, and respectful tone.

Summary Takeaway

Volcanoes are ancient, powerful, and ever-present forces shaping our planet in dramatic ways. While they can be dangerous and unpredictable, they are also a vital part of Earth’s story—creating land, enriching soil, and providing energy. As Professor Sigmundsson emphasizes, understanding volcanoes helps us appreciate both their hazards and their wonders. "They are beautiful, spectacular... if you stare at them for a long time, stare into the red glow, you can be charmed." ([24:45])