Death Cry of an Iceberg

I love the sound that ice makes when you pour warm water on it—that splitting, rending, singing sound. It turns out that an iceberg the size of an island will make those same noises when it melts and cracks apart. But the sound, like the ice, is much, much bigger.

Listen to this story for VOA News about a team of scientists who were listening for underwater volcanoes in Antarctica when they overheard an iceberg being born, living, and dying:

Here’s the written version of the story.

Here’s something to think about: sound is vibration of molecules. It travels in waves of moving particles that bump into each other, creating the buzz you hear as sound.

Sound travels just fine in air: there are tons of particles in the Earth’s atmosphere. If a tree falls in a forest and there’s no one there to hear it, it does make … something. The air vibrates, but there are no ears to interpret it.

Sound doesn’t travel in space. A tree falls in space and nothing vibrates at all. There’s nothing to vibrate. Space is, famously, a vacuum. There are next to no particles to move around and bump each other. This is why sci-fi movies should never have noisy space scenes: space is totally silent to us.

But water is just about the opposite. Water is dense, particulate, and syrupy. Sound zips right through water, traveling four times faster and farther than it would in air. That’s why—as one of my favorite scientists Chris Clark has said—if you live in the ocean, you listen. Light decays and sight is difficult. Smell gets washed away. But in the ocean sound is everywhere, and bounteous, and large.

I went out on a limb and called Chris for this story, and was really jazzed to get a chance to interview him. He’s one of the most eloquent educators I’ve ever heard, and he studies the interaction of marine animals with their acoustic environment—which is an environment that humans are stepping on. The drone of ships and clang of sonar. We can’t hear the sound we make underwater, so we tend not to care. But everyone else can hear us, and only us. The whales stop calling when a ship goes by. A ship goes by many times a day. It’s like living under strobe lights.

Melting icebergs aren’t such a problem. Even if one is as loud as an earthquake and can be heard at the equator, it still only rumbles for 20 minutes or so. But the ships keep going by.

Here’s the original article about the iceberg.

Here’s an article I wrote about Chris’s work awhile ago.