Podcast Episode Summary

Podcast: But Why: A Podcast for Curious Kids
Episode: How Are Glaciers Formed?
Date: September 5, 2025
Host: Jane Lindholm (Vermont Public)
Guest Expert: Professor Gevutfina Atelgersdotter, Glaciologist, University of Iceland

Overview

This episode of "But Why: A Podcast for Curious Kids" answers kids' questions about glaciers: how they are formed, how they move, what colors they can be, and how they shape the landscape. Host Jane Lindholm visits Iceland's Solheima Jokull glacier and talks with Professor Gevutfina Atelgersdotter, an expert glaciologist, to delve into the fascinating world of glaciers—how they’re made, why they move, their role in shaping our planet, and why they’re rapidly shrinking due to climate change.

Key Discussion Points & Insights

1. What Is a Glacier and How Is It Formed?

[05:25–07:30]

• A glacier is formed from snow that doesn't melt over summer, accumulating year after year.
• Over time, the accumulated snow becomes compacted under its own weight, turning into dense ice.
• When the ice is thick enough, it starts to deform and move under its own weight, turning from a snowfield into a flowing glacier.
• Notable Quote:

  "A glacier is ice, and the ice is formed because the precipitation of last winter didn’t melt in the following summer... Once that has become densified so that the snow that was fluffy and flurry in the beginning is compacted into glacier ice, then it can start to flow."
  — Professor Gevutfina Atelgersdotter, [05:48]

2. Glaciers Only Form on Land

[08:00–08:35]

• Glaciers form only on land, while icebergs often originate from glaciers as chunks that break off and float in the sea.
• The oldest glacier ice can be found at the edge (“snout”) of the glacier, pushed forward by newly compacted ice from above.

3. How Old Are Glaciers?

[08:54–09:48]

• Glacier age varies:
  • Icelandic glaciers: ~800–900 years old
  • Greenland’s ice: up to 130,000 years
  • Antarctica: ice older than one million years
• Glacier ice serves as a time capsule, preserving records of ancient climate in trapped air bubbles.

4. Why Are Glaciers Different Colors (Like Pink)?

[10:20–12:49]

• Pink coloration is due to algae, which can survive on cold ice and possess red pigments (carotenoids) acting as ‘sunscreen’.
• This pigment helps algae protect themselves from UV but also absorbs more heat, causing glaciers to melt faster.
• Glaciers may also appear blue (from dense, old ice), white, black (from volcanic sand), brown, or yellowish (from Saharan dust).
• Notable Quote:

  "The algae itself is green, but it has a secondary red pigment called a carotenoid. In the summer, the algae can turn on their red pigments as a protective barrier against UV radiation from the sun... that leads to glaciers that melt faster than white ones."
  — Jane Lindholm, [11:13]

5. How Do Glaciers Move and Shape the Landscape?

[17:06–19:45]

• Glaciers act like bulldozers, pushing rocks, soil, and sand ahead of them (forming moraines).
• They carve U-shaped valleys by grinding the bedrock as they move.
• Notable Quote:

  "They are really like bulldozers... they create what we call frontal moraines... If a glacier fills a valley, it carves it into more like a U-shape."
  — Professor Gevutfina Atelgersdotter, [17:41]

• Evidence of past glaciers can be read by looking at landscape features such as moraines and U-shaped valleys.

6. Glaciers as Climate Indicators; Rapid Shrinking and Climate Change

[20:35–25:02]

• Glaciers have always grown and shrunk in response to natural cycles, but current shrinkage is much faster due to man-made climate change.
• The industrial era (~last 150 years) and fossil fuel use have increased global temperatures by ~1.1°C, accelerating glacial melt worldwide.
• If warming stopped now, many glaciers would still become about 40% smaller due to delayed response.
• Importance: Glaciers are sensitive record-keepers of climate and provide clear evidence the planet is warming unusually quickly.
• Notable Quote:

  "All the glaciers in the world are responding. We have already warmed the planet, on average, 1.1 degree. And all the glaciers are telling us that they can feel that."
  — Professor Gevutfina Atelgersdotter, [23:39]

7. Glaciers in Unlikely Places: The Tropics and High Mountains

[16:21–16:54]

• Glaciers aren’t just found in cold regions; they exist in the tropics on tall mountains (e.g., Kilimanjaro), as long as snow accumulation outpaces melting.

8. Glaciers as a Call to Action

[26:11–27:17]

• There are alternative, renewable energy sources (solar, wind, tidal, geothermal) that don’t emit CO2, but transitioning away from fossil fuels is a policy challenge.
• The ongoing melting of glaciers emphasizes the urgency of moving to sustainable energy.
• Notable Quote:

  "We really need to move into this renewable energy regime because we understand that the regime that we have had in the last 150 years is both not good for the climate and it's also not sustainable because we're going to run out of those fossil fuels anyway."
  — Professor Gevutfina Atelgersdotter, [27:08]

Notable Quotes & Memorable Moments

• On the thrill of glaciology:
  "I became a glaciologist because I'm really interested in skiing... I measure the glaciers. I model them."
  — Professor Gevutfina Atelgersdotter, [03:01]

• On glacier safety (and a fun story!):
  "For example, this spring... I could be towed behind the car in that trip... then when everybody went home, I skied down the glacier. So that was a great ski trip, but a measuring trip at the same time."
  — Professor Gevutfina Atelgersdotter, [04:11]
  Co-host reminder: Don’t try this at home! [04:53]

• On glacier loss:
  "So now 30 years, it's getting shorter, sometimes 50, up to 100 meters a year."
  — Professor Gevutfina Atelgersdotter, [15:39]

• On glacial landscape learning:
  "We see in Solheimoyukul... how big the glacier was because the vegetation hasn't come yet. The landscape is really telling us how big the glaciers were and how extensive they were."
  — Professor Gevutfina Atelgersdotter, [19:45]

Timestamps for Important Segments

| Timestamp | Segment | |-----------|------------------------------------------------------------| | 01:37 | Host introduces the glacier in Iceland | | 05:25 | Kids ask: How are glaciers formed? | | 05:48 | What is a glacier? (Professor’s explanation) | | 08:54 | How old are glaciers? | | 10:20 | Why do glaciers turn pink? (Algae and coloration) | | 12:13 | Other glacier colors and causes | | 14:14 | Discussing Solheima Jokull and glacier shrinkage | | 17:06 | How glaciers shape the land (bulldozers, moraines, valleys)| | 20:35 | The current shrinking of glaciers and climate change | | 23:39 | Glaciers as early climate warning systems | | 26:11 | Renewable energy and the need for a transition |

Tone & Language

The episode maintains a friendly, conversational, and engaging tone aimed at children and families, blending scientific explanations with relatable analogies (like comparing glaciers to honey or a “bulldozer”), anecdotes about fieldwork, and plenty of encouragement for curiosity.

Conclusion

This episode skillfully demystifies glaciers—how they form, move, and shape the Earth—while underscoring their importance as visible indicators of a changing climate. Through clear explanations and real-world analogies, Professor Gevutfina Atelgersdotter inspires wonder about glaciers and urges swift action on climate change. Perfect listening for curious minds young and old.