Son Doong

We are descending through the mouth of a cave, somewhere in the remote jungle of Vietnam. We are going down into the largest cave that exists on this planet: Son Doong.

The entrance to Son Doong is a slippery slope that leads down onto the floor of the massive caverns of the cave. This is not a place you want to explore without a flashlight. 

As we continue downward with the exploration team, we are going to switch on the lights - to be able to see what the cave looks like.

A stalagmite is a type of rock formation rising from the floor of a cave. It might look like a mushroom, but these stalagmites actually form from water and sediment dripping from the roof of the cave. 

If you look toward the entrance, in the distance, you can see some of the expedition team members coming down the slope. Can you see them? Several of them are wearing headlamps.

You are now standing on top of a large stalagmite! It might actually be the tallest stalagmite in the world, rising high above the cave floor. That’s why the view is so good from up here.

All around you are other stalagmites that have slowly formed over thousands of years. This is also one of the largest chambers of the Son Doong cave. This passage is large enough that a large Boeing 747 airplane could fly through it.

You are standing on top of a thin stalagmite, called the Hand of Dog. It is over 70 meters tall, which makes it one of the tallest ones in the world. Don’t fall off!

Green plants, inside the cave? How is this possible? If you look up, you can see an opening. At some point in history the cave ceiling became too weak, and collapsed, revealing this large hole into the cave. 

Thanks to the sunlight that comes in from above, the floor of the cave is covered in green plants.
When the scientists first found this section of the cave, they were amazed to find such a landscape inside.

It looks like something out of the jurassic era, where one would expect to find pre-historic creatures. That is indeed why the scientists named this section of the cave: ‘Watch out for dinosaurs”.

You're now standing in the short section between the two collapsed sinkholes of Son Doong. This section of the cave is pure fossil and has been relatively undisturbed for a long time, compared to other sections of the cave. 

Several of the other sections of the cave have been flooded over and over again, but not this section.

Determining the exact age of Son Doong is hard. The cave system has formed during such an extremely long time, the river slowly carving away at the soft limestone. This means Son Doong is between 2 and 5 million years old.

The passage between the first and second doline (the sinkholes) is just a few hundred meters. Compared to the dolines, this is a barren landscape that doesn't get any sunlight at all.

Without the artificial lighting from the expedition team’s flashlights, you would be standing in a very dark space. Up ahead, you can see the large opening leading into the green landscape of the second doline.

One of the expedition team members is standing on top of a large flowstone, looking around with one of the strong flashlights.

We are now walking up toward the second large doline, or sinkhole, of Son Doong. We are coming out of the darkness, and right here is just as far as the sunlight reaches.

The expedition team is up ahead, ready to ascend into the forest of the second doline. You can already see the bright sunlight coming in from up ahead.

This is a huge flowstone. Flowstones are created over vast periods of time, while water dripping from the cave ceiling creates sheetlike deposits of calcite that turn into massive blocks like this.

This is the Garden of Edam, named after the paradise of Adam and Eve. This doline is much larger than Watch out for Dinosaurs, at about 163 meters across the base, and has a thicker forest similar to the jungle above. 

Scientists estimate this doline collapsed because it is located at the intersection of two major fault lines.

The combination of these two fault lines became too unstable, and led to such a massive collapse of the cave ceiling. Today the doline holds a veritable forest of its own, hosting tall trees and a forgiving landscape for birds and bugs alike.

In geology, a fault is a 'fracture' in rock as a result of the Earth's movement. A fault line is the surface trace of a fault, the line of intersection between the fault plane and the Earth's surface. These diagonal lines in the rock are evidence of the movement of our planet.

Standing in the middle of a jungle like this, it's hard to remember you are still inside a cave. Compared to the first doline, this is a forest where you can easily get lost. 

The vast jungle surrounding Son Doong is home to a wide variety of wildlife, some of which has spilled over into the cave. Birds, monkeys and even snakes have been spotted in the cave by the explorers.

But they have found no evidence of people entering the cave before its discovery in 2009.
Due to the very recent discovery of the cave there is still very little documentation on the species found within .

This is as far as the expedition takes us, deep inside the darkness at the end of Son Doong.
A lingering mystery is the origin of the river water flowing through this area of the cave, called Passchendaele.

While all the water flowing through the first section of the cave, up to the first doline, has been mapped - experts are still trying to figure out where the innermost waters flow from.

With the massive volumes of water passing through this section, the question is whether this water comes from an even larger cave - one that hasn't yet been discovered.