Look down through the ice on Lake Baikal and you may feel as though you are looking through glass.

White bubbles hang underneath your feet.

Some are tiny.

Some are large and round.

Others form long columns that seem to rise from deep below the frozen lake.

They look like little pearls trapped inside crystal.

But they are not really “ice bubbles.”

They are gas bubbles trapped in ice—and many of the famous ones contain methane. NASA's explanation of the phenomenon describes methane rising through Lake Baikal and becoming frozen into the exceptionally clear winter ice.

So where does the gas come from?

Why does it rise?

And why does the ice trap it so neatly instead of letting it escape?

The answer begins at the bottom of the lake.

There, sediments can produce methane. The gas moves upward through the water. Then winter arrives, the surface freezes, and the rising bubbles meet a growing sheet of ice.

Some of them get caught.

And because Baikal's ice can become remarkably clear, you can still see exactly where they were trapped.

 The first place to look is not the ice.

It is the lake floor.

Lake Baikal contains methane in its sediments, and the lake has many areas where gas can seep upward through the water. Researchers have directly observed methane bubbles and methane hydrates rising from Baikal's sediments.

But why is there methane down there?

Part of it comes from the natural breakdown of organic material in the sediments.

As microorganisms break down organic matter without oxygen, methane can be produced.

The gas then moves through the sediment and enters the water.

If enough gas gathers, it can escape as bubbles.

Think of opening a fizzy drink.

The gas does not all stay dissolved.

Some escapes as bubbles and rises.

Lake Baikal is doing something similar, although on a much larger natural scale.

The difference is that the gas is coming from beneath the lake rather than from a bottle.

And the bubbles have a long way to travel.

Lake Baikal is extraordinarily deep, reaching about 1,642 metres.

Most bubbles would never survive that entire journey unchanged.

Some dissolve back into the water.

Others continue upward.

And under the right conditions, some methane can make it close enough to the surface to become part of the frozen ice.

That is where the famous bubbles begin.

 Now imagine a bubble rising toward a lake that is beginning to freeze.

At first, the surface is open water.

The gas can escape.

Then ice begins to form.

As water freezes, most dissolved gases do not fit easily into the growing ice crystal structure. They are pushed out of the freezing water. But some gas can collect into tiny bubbles near the freezing front and become trapped as the ice continues to grow. Laboratory research has shown how freezing ice can capture and reshape gas bubbles.

This happens layer by layer.

A little more ice forms.

Another layer traps gas.

More ice grows.

Another bubble is caught.

That is why some Baikal bubbles appear stacked in columns.

They can record repeated gas release while the ice was forming.

The shape of a bubble can even tell scientists something about the freezing process.

A slowly growing bubble has time to change shape.

A bubble trapped quickly may look different.

Research on bubble shapes in ice has shown that these forms can contain information about how quickly the ice formed and how much gas was dissolved in the water.

So the ice is doing more than freezing.

It is recording what was happening in the water while it froze.

And that record remains visible long after the bubble has been trapped.

 The bubbles would not look nearly as spectacular if the ice around them were cloudy.

That is the other half of the trick.

Baikal can produce stretches of remarkably transparent winter ice. NASA specifically describes the methane bubbles as being frozen into exceptionally clear ice.

Clear ice lets light pass through it.

That means you can see into the ice instead of seeing only its white surface.

When light encounters bubbles, cracks and other structures inside the ice, some of it is scattered. The gas bubbles therefore stand out against the darker blue ice around them.

That is why they can look like white coins or pearls.

The bubbles themselves are not necessarily white gas.

Their appearance comes partly from the way light interacts with the bubble and surrounding ice.

You can see the same basic idea in foam.

A single tiny bubble is hard to notice.

A huge collection of bubbles suddenly becomes bright.

Lake Baikal simply gives you a gigantic natural version of the effect.

A clear sheet of ice.

Thousands of trapped bubbles.

And sunlight passing through the whole thing.

 Look closely at photographs of Baikal ice.

The bubbles are not always scattered randomly.

Some appear one above another.

A small bubble.

Then another.

Then another.

Together they form a vertical line.

Why?

Because the gas source below can remain active while the ice is forming.

A steady seep can send bubbles upward from roughly the same area again and again. If the ice is growing during the same period, new bubbles can become trapped above older ones.

The result is a kind of frozen trail.

Researchers studying Lake Baikal have found gas seeps and observed rising bubbles, while studies of Baikal's unusual ice structures have linked some forms to methane transport from below the lake.

But there is an important detail.

Not every bubble pattern in Baikal ice has to come from methane.

Later research on Baikal's ice found that some vertical bubble structures are produced by changes in the ice itself during spring melting and sunlight-driven metamorphism, rather than directly by methane activity in the sediments.

So when you see a beautiful column of bubbles, it is better not to assume that every single bubble has the same origin.

Some are records of gas moving upward.

Others can be created by changes happening inside the ice.

The photograph may look simple.

The physics is not.

 Lake Baikal has another reason to make scientists look twice.

It contains methane hydrates.

These are solid, ice-like structures in which methane molecules are trapped inside a cage made of water molecules.

They form under the right combination of pressure and temperature, especially in deep sediments.

Lake Baikal is unusual because methane hydrates occur in its deep sediments, and researchers have directly observed methane hydrate fragments rising through the water.

That matters because a normal methane bubble and a methane hydrate are not quite the same thing.

A small gas bubble can dissolve as it rises through deep water.

A methane hydrate is much more stable under the right conditions.

The 2019 study proposed that rising methane hydrates can carry methane upward and that their interaction with freezing water may help produce some unusual Baikal ice structures.

Scientists even found unusually high methane concentrations in certain types of unusual ice associated with these processes.

So the famous bubble photographs are connected to a much bigger system.

Methane is moving through the lake.

Ice is forming above it.

And sometimes the gas does not travel in the simple form we might imagine.

It can travel as part of a solid hydrate structure.

That makes Lake Baikal more than a beautiful winter photograph.

It is also a place where scientists can watch methane move through a very unusual freshwater environment.

 Now look at the bubbles one more time.

A photograph makes them look decorative.

A scientist can see something else.

Information.

The shape, size and position of bubbles can tell researchers about how the ice formed and how much gas was present in the water. Laboratory experiments have shown that bubble shape changes with freezing speed and dissolved gas conditions.

The ice can therefore preserve a little history.

A bubble trapped near the surface formed at one moment.

Another trapped deeper down may have been caught earlier.

A column can suggest repeated gas release.

A strange shape can reveal something about how quickly the surrounding ice froze.

And unusual concentrations of methane in some Baikal ice structures can provide clues about how methane moves through the lake.

This is why those bubbles are more than a beautiful winter curiosity.

They are evidence.

They tell scientists something about what happened before the lake became completely frozen.

And the clearest ice makes that evidence unusually easy to see.

So when you look through Baikal's winter surface, you are not simply looking into a frozen lake.

You are looking at a record of what happened while the lake was freezing.

So, Why Does Lake Baikal Have Those Crystal Ice Bubbles?

The answer starts deep below the surface.

Methane can form in lake sediments.

Gas can rise through the water.

Winter freezes the lake from above.

As the ice grows, some bubbles become trapped.

And Baikal's unusually clear ice lets you see them.

Some form single white spheres.

Some line up into columns.

Some become distorted as the ice around them changes.

And some unusual structures are linked to methane hydrates rather than ordinary gas bubbles.

There is one final correction worth remembering.

The bubbles are not made of ice.

The ice is around them.

The bubbles are gas trapped inside it.

That small difference explains the whole phenomenon.

The lake produces the gas.

Winter provides the trap.

And the clear ice turns the hidden process into something you can actually see.

What looks like a collection of pearls beneath your feet is really a frozen record of the lake breathing gas upward from below.

Frequently Asked Questions

1. Why does Lake Baikal have bubbles trapped in its ice?

Gas released from the lake and its sediments can rise toward the surface. When the lake freezes, some of that gas becomes trapped in the growing ice. NASA identifies many of the famous visible bubbles as methane.

2. Are the bubbles in Lake Baikal made of methane?

Many of the famous bubbles are methane bubbles. Lake Baikal also contains methane hydrates, and researchers have linked some unusual ice structures to methane transport from below. However, not every bubble structure in Baikal ice necessarily has the same origin.

3. Where does the methane come from?

Methane can be produced in lake sediments when microorganisms break down organic material under oxygen-poor conditions. Lake Baikal also has numerous gas seeps where methane-rich gases move upward through the water.

4. Why don't the methane bubbles simply escape?

Some do. Many ordinary methane bubbles can dissolve back into the water as they rise. But some gas reaches the surface during ice formation and becomes trapped in the growing ice. Methane hydrates can also transport methane upward under suitable conditions.

5. Why is Lake Baikal's ice so clear?

Baikal can produce exceptionally clear winter ice, allowing structures beneath the surface to remain visible. NASA specifically describes the famous methane bubbles as being trapped in exceptionally clear ice.

6. Why do some bubbles form long vertical columns?

Repeated gas release from a similar location can produce streams of bubbles. If the surface is freezing at the same time, successive bubbles can become trapped above one another, creating columns.

7. Are all the strange bubble patterns in Baikal caused by methane?

No. Research on Baikal ice has shown that some vertical bubble structures can also form during changes in the ice caused by sunlight and melting, rather than directly from methane activity in the sediments.

8. Why do some bubbles look flat instead of round?

A trapped bubble can change shape as the surrounding ice freezes and presses against it. Research on ice bubbles shows that their shapes depend on factors such as freezing conditions, bubble growth and dissolved gas.

9. Does Lake Baikal contain methane hydrates?

Yes. Scientists have found methane hydrates in Baikal's deep sediments and have directly observed hydrate fragments rising through the lake under some conditions.

10. Why do scientists study these bubbles?

The bubbles can provide information about gas movement, methane release and how the ice formed. Their shapes, positions and concentrations can act as clues to processes happening inside the lake and during freezing.