Hi guys, today I’ll be discussing and showing you an ancient underwater site, which I guarantee
you’ve never heard of. This amazing Chinese site is called Shiyan Cave, which is probably
the largest underwater stone “quarry” in the world. Besides its impressive machine
marks, there are two fascinating facts about this site, which leads me to believe it was
created by a prehistory civilization. Let’s dive in.
Shiyan cave is said to be over 1,000 years old. It is located on Mount Xiqiao park in
southern China, close to the South China Sea. Mount Xiqiao is no ordinary mountain - it’s
a 40- 50-million-year-old extinct volcano situated between two major rivers on the Pearl
River Delta. Stone tools found at Mount Xiqiao prove human activity in the region existed
between 6,000 to 8,000 years ago. Covering an area of 14 square kilometers or 5.4 sq
miles, Mount Xiqiao has many springs and peaks with the highest peak at 346 m.
Shiyan cave is located on one of the peaks that is over 100m or 300’ high. It is claimed
to be an ancient quarry that was closed due to flooding. From afar, the entry to the cave
is obscured by trees. When approaching the cave, you see a wide yet intricate opening
in the form of a big horizontal crack. When you walk inside, you are amazed by the cave’s
carved out spaciousness. The grand hall can likely hold a thousand people despite its
small appearance from the outside. Walking further inside, you find a stream
with boats. Here are 3 impressive man-made caverns submerged in water at a 100m high
altitude – all of this btw is inside an extinct volcano. Currently the park offers
boat tours into the submerged cave which is about 200m or over 650’ into the ancient
quarry. But where did the water originate from and how deep is it? Nobody seems to know.
It wasn’t until 2009 when a group of cave divers first reported this underwater discovery.
What the divers found shocked them. The cave is immense, with an estimated area of 60,000
square meters, or 6.5 million square feet which is 15 acres. Because the inner cave
is submerged by water, it avoided natural weathering and man-made damage. The site is
extremely well preserved with clear water. There are countless steps descending into
the lower potion of the cave. Following the steps, the divers saw stone slabs put together
which seemed to be leftover products from long ago. These slabs look like the ones used
as pavement in ancient China. This underwater cave is complicated with multiple sections
and connecting passages. The divers also found oil lamp stands, bowls and bamboo ladders.
Archaeologists used laser and sonar scanning to create a 3D model of Shiyan Cave. The bottom
of the cave is covered by a thick layer of silt. Archaeologists inferred that there may
be greater secrets still hidden and unrevealed. Mystery No. 1: Tool Marks
Looking at the footage and photos, I couldn’t help but notice the familiar, large and uniformed
tool marks on the almost straight cave walls. These markings are fairly identical to those
found at Yangshan Quarry, Baalbeck, Petra and many other ancient sites. In a previous
video, I explained why such marks could not be created by hand tools like chisels with
this level of accuracy and consistency. Please click above to see that video. I think these
marks resemble modern machine marks. Since the underwater cave was rediscovered not long
ago and stayed untouched, we know these machine marks are not recent and must have been there
for millennia. The cave was probably rediscovered 1,000 years ago and used as quarries. The
ancient Chinese masons likely never ventured into the deeper portions of this 15-acre cave
because it would have been difficult to work there with oil lamps and to transport slabs.
The thin stone slabs and rubble-piled steps show crude and inferior masonry methods as
opposed to the sophisticated uniformed tool marks on the walls. We can tell that these
two were not done by the same workers. This leads me to the theory that this cave is another
megalithic structure created by a prehistory advanced civilization.
So far divers haven’t reached the bottom of the cave. The deepest they have gone is
40m, which is about the height of a 13-story building. Shiyan cave is on top of a hill
and the cave water is at an altitude of over 100m. The water table at the two nearby rivers
is less than 3m above sea level, which means the cave water table is 100m higher than the
regional water table. Unbelievable! Mystery No. 2: The Puzzling Water
Where did the water originate? How come the water table in the cave is much higher than
the nearby rivers? Is the cave possibly part of a perched aquifer? A perched aquifer sits
above the regional water table, with an unsaturated zone below. But perched aquifers are typically
very small and are only replenished by local precipitation. The way Shiyan cave was excavated
it gets no precipitation; however, the cave water table remains stable. Also, it contains
too much water to be a perched aquifer. So where did the water come from?
Remember that Mount Xiqiao has many springs. It turns out that some are artesian springs.
In most cases water flows downhill due to gravity. But artesian water flows up to the
land surface because the underground pressure forces the water upwards. An artesian aquifer
has confined water, surrounded by layers of impermeable rock or clay which apply positive
pressure to the water contained within the aquifer. If a well or spring were to be sunk
into an artesian aquifer, water in the well-pipe would rise to a height corresponding to the
point where hydrostatic equilibrium is reached; like the springs we see at Mount Xiqiao. This
means there is at least one confined artesian aquifer inside the extinct volcano. If Shiyan
cave is connected to this aquifer, that could explain why the cave water is 100 meters higher
than the regional water table. The water here is well worth testing for analysis, which
might reveal further clues of the cave’s history.
A local archeologist believes that the flooding of the cave was a long-term process, maybe
over hundreds of years, because they found neither human remains nor masonry tools in
the cave. Whoever worked in the cave had prepared for the flooding by retreating to safer ground
before water came in. Then when did the water enter the cave? When
was the cave 1st excavated? Was the cave created before the formation of the artesian aquifer?
I say no – or the major geological movement that formed the aquifer would have shattered
the cave. If the aquifer was present during the excavation of the cave, does that mean
the cave was flooded and the work was done underwater?
Not necessarily. Perhaps in prehistory times the ancient workers accidentally broke the
impermeable layer of the artesian aquifer which caused the flooding. Maybe a few hundred
years ago the Chinese workers did so. Or maybe, just maybe the cave was excavated when the
aquifer was frozen. The Last Glacial Period started about 110,000
years ago and lasted for over 100,000 years. There were periods such as the Last Glacial
Maximum when Mount Xiqiao was potentially covered with ice and the aquifers would have
been frozen. If the cave was excavated during this freezing time period, then there would
be no flooding issues. Nowadays most artesian aquifers around the world are perpetually
replenished by the ongoing flow of rain and groundwater. One can imagine that after the
end of the Last Glacial Period, the temperatures rose dramatically as the aquifer started to
unfreeze. At the same time, the sea level went up which could have pushed the groundwater
level up, also the warming climate brought more rain; together the artesian aquifer inside
Mount Xiqiao was replenished. Then the Shiyan cave over time due to warmer weather became
flooded. Mystery No. 3: The Purpose of the Cave
From tool marks on the walls, we can tell this process could have produced crushed stone
instead of stone blocks or slabs. The modern machines that can create similar marks are
used for mining. Today crushed stone is a cheap product since stone is widely distributed
all around the world, mostly used as construction material in concrete and asphalt. If crushed
stone was the final product that ancient workers were after, then why didn’t they just use
an open pit quarry which would be easier and safer. What would’ve been the point of taking
great trouble making a complex underground quarry for easily accessible crushed stone?
It makes no sense. The site sits atop a hill, quarrying inside a cave on a hill means almost
doubling the work: hauling the crushed stone out of the deep cave and down a mountainside.
That seems counter-productive. We can see the cave layout is unusual with
multiple chambers and connecting pathways. The cave has different portions with different
elevations. If the site was designed to be a quarry for mining stone, then why not keep
it simple and flat? Why make the chambers at various depths? The different elevations
would make it more difficult to transport stone out.
The complicated layout has me thinking the cave was not originally excavated as a quarry.
Possibly ancient workers were mining something more valuable than crushed stone. The irregular
shapes of the caves could be the result of searching and mining for special minerals
or precious metals. Mount Xiqiao is an extinct volcano. Volcanoes
directly or indirectly produce or host deposits of many minerals and metals. It happens that
not far from Shiyan cave, on Mount Xiqiao, a large good grade silver deposit was found
in a layer of breccia tuff. There is also a high rate of rare earth content here.
A hill about 10 miles away from Mount Xiqiao has a large gold deposit and a separate even
larger high-grade silver deposit. The ores have already been assessed and the mining
work has begun. The ores are said to be formed through multiple geothermal deposition and
silicification, which means the Xiqiao volcano helped form the ores.
Could Shiyan cave actually be a prehistory mine? Based on the presence of large deposits
of silver and gold nearby, it’s very possible that Mount Xiqiao contained precious metal
and minerals which were mined by a lost ancient civilization over 12,000 years ago during
the Last Glacial Period. The well-preserved site at Shiyan Cave might
provide invaluable evidence to study this lost civilization. Underwater archaeology
experts and more in-depth research are still needed to further reveal this amazing mystery.
If you have any insights, please leave me a comment. If you like my video, please give
me a thumb’s up and subscribe. I have a wide range of topics that I want to share
with you. This is Curious Being, I am Tina. Thanks for watching and see you next time.