The slope leads down, down into the darkness.
Into the Unknown
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.
This hole, through which we just entered, wasn’t discovered until very recently. A local Vietnamese farmer, named Ho Khanh, found this hole in the 1990s. But it wasn’t until 2009 that a team of British cave explorers finally went here and discovered the large cave beyond.
Turning the Lights On
Inside Son Doong, the fantastic features of its inner chambers are revealed.
We can see all of this because of three very powerful flashlights that the expedition team has brought with them. Without these flashlights, you wouldn’t be able to see anything in the darkness.
Look around at one of the many stalagmites formed during the thousands of years this cave has remained undisturbed from human touch. This is just the beginning.
The Cave Ceiling
The chamber you're standing in is over 50 meters, or about 150 feet, tall. This is actually just the beginning of the cave, and one of the more tight spaces. It’s about to get much larger.
The mushroom-like stalagmite
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.
Over many thousands of years, the sediment slowly hardens and becomes stalagmites like this one.
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.
The Hand of Dog
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.
The Expedition Camp
This is the camp of the expedition that is moving through the cave. Can you see the tents? To create these images from the cave, over 50 people were involved - photographers, cave researchers, guides, cooks, porters and other expedition staff.
The Woman With the Light
Can you see the woman standing there with a flashlight? She looks very small in this very large cavern and this gives you an idea of the scale of the space.
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!
Watch Out For Dinosaurs
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”.
The Spiral Stalagmite
This beautiful formation has formed over thousands of years, as water has dripped down from the ceiling above. When you stand on top of the stalagmite, you can feel the water dripping even today. The stalagmites continue to grow.
Seeing green plants like this inside a cave is very rare. Usually caves are dark places. Without sunlight plants cannot go through photosynthesis, a process which allows plants to absorb energy from light.
But thanks to the opening in the cave ceiling above, there is light, enabling photosynthesis.
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.
Since this part of the cave has been somewhat undisturbed by the elements, it has been possible for the beautiful gours you can see all around you to form. These delicate gours, also called rimstone, formed from water dripping from the ceiling.
The rimstone consists of calcite and other minerals that have hardened over a long time.
Person on the Stalagmite
Can you make out the person on top of the stalagmite? He’s really small at this distance! The people in the pictures help give scale to these massive caverns.
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.
These massive shapes you can see all over the cave are called flowstones. Where water flows and trickles down the walls of the cave, these flowstone form of all the accumulated calcite and minerals. Formations like flowstones are very common in limestone caves like Son Doong.
The Expedition Team
The expedition team walking up into the light are on their way into the second doline. As you can see, there is a small trail here.
This is because several expeditions, with scientists, have already been inside the cave. We can see this trail is an impact from the sudden human presence in the cave.
One of the expedition team members is standing on top of a large flowstone, looking around with one of the strong flashlights.
Into the Light
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.
Phytokarst is the name for this type of rock, that seems to be growing toward the light. However, it is the other way around. The limestone rocks are slowly being eroded by microflora that's excreting acid into the rock, which is creating these fantastic formations.
The small plants
We are standing at the edge of the sunlight’s range. Looking back into the dark of the cave, there are no plants. This is the line between life and death for plants, where they only get sun for a few minutes each day.
As we walk up into the light, the plants have more sunlight and grow much larger.
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.
Garden of Edam
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.
The Collapsed Ceiling
The opening is a few hundred meters wide. Rainwater and sun come into the cave. Some of the jungle from above is almost falling in.
The Son Doong ecosystem is connected to the jungle above. Scientists have not found any new plant species in the cave, but they found new species of insects, including a white woodlouse.
The Tall Trees
Thanks to the very protected surroundings, surrounded by rock on all sides, the forest inside the Garden of Edam has been able to grow quite tall. Some of the trees here are over 30 meters tall.
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 .
The Ring of Light
It’s really hard to understand this jungle is actually inside the largest cave on the planet - right? The only way to remember is to look up. When you look up, you see the ring of light that is the hole in the ceiling of the cave.
The End of Son Doong
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.
This passage is normally a muddy trench, leading into the last stretch of the cave. Now, because of heavy rains, this section has flooded and formed a lake. The scientists and cave explorers have still not been able to map where all this water comes from.