World's Largest Iceberg Runs Aground

Episode

03/20/2025

The seals and penguins of South Georgia have had a lucky escape from the world’s largest iceberg!

Transcript

The remote island of South Georgia in the South Atlantic Ocean is home to fur seals, elephant seals, and king penguins…

Like, millions of king penguins!

But until recently, there were fears that these animals could be at risk from something huge headed their way. A23a: the world’s largest iceberg.

Icebergs form when large chunks of ice break off glaciers or ice sheets. This is called calving. A23a calved from an Antarctic ice sheet back in 1986, but got stuck on the seafloor for many years.

Then, in 2020, it started drifting again, in the direction of South Georgia, before running aground in March this year, in the shallow waters around the island.

At its peak, A23a measured more than fifteen hundred square miles—almost five times the size of New York City. Experts warned that all that ice might pose a risk to seals and penguins, by blocking their access to feeding grounds.

In the end, however, the iceberg stopped far enough away that most animals are unlikely to be harmed. In fact, there may be an upside to having a "megaberg" nearby.

As icebergs melt and break up, they release lots of nutrients. This helps tiny plankton to grow, providing food for small animals, which are eaten by larger animals, and so on, all the way up the food chain.

So, as A23a melts over the coming months, it could boost food for the whole island. A final chapter for the world’s largest iceberg.

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World's Largest Iceberg Runs Aground

Teaching overview

Learning points

The world’s largest iceberg, A23a, has run aground near the island of South Georgia.
Icebergs form when large chunks of ice break off glaciers or ice sheets, a process known as calving.
As A23a iceberg melts, it will release nutrients into the ocean, which could increase food for the whole food chain.

Curriculum keywords

iceberg
wildlife
food chain

Spark a discussion

How do icebergs form?
Why did experts warn that penguins and seals could be in danger from A23a?
Why might A23a benefit the wildlife of South Georgia?

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World's Largest Iceberg Runs Aground

Transcript

Teaching overview

Learning points

Curriculum keywords

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Classroom Resources

Video Viewing Guide

Make Your Own Science Episode

Language and Literacy Activities

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