Archaeological Shiyanyan "Underwater Mystery Cave"
He promoted the research and development of underwater archaeological technology and hoped that the Xiqiao Mountain Shiyanyan Site would be declared a World Heritage Site
Cui Yong is the deputy director of the Guangdong Provincial Institute of Cultural Relics and Archaeology and a well-known underwater archaeology expert in China.
For the past 15 years, he has been following the underwater archaeological work at the Shiyanyan Site in Xiqiao Mountain, Foshan City.
This is a quarry that was first mined in the Song Dynasty and large-scale mined in the Ming and Qing Dynasties. It was accidentally submerged by underground lake water and survived intact.
Under the continuous scientific research of Cui Yonghe's team, this site was selected as a national key cultural relics protection unit in 2019.
Cui Yong will retire next year, but he still finds it difficult to give up the underwater archaeological project that he has spent many years in.
In his opinion, this underwater site with an area of over one million square meters is currently the largest ancient human industrial site in China, and it will be fully qualified to be declared a World Heritage Site in the future.
Text, picture/Guangzhou Daily full media reporter Xiao Huanhuan, intern Li Yuanmeng (except for signature)
Accidentally found "Underwater Dragon Palace"
One day in 2006, Cui Yong, who has been engaged in underwater archaeology for nearly 20 years, told technical partners Zhang Song, Dong Guoliang and others about Shiyanyan in Xiqiao Mountain. They and several partners went to Xiqiao Mountain with diving equipment and became The first group of professionals in China to conduct underwater exploration of Shiyanyan Rock in Xiqiao Mountain.
"Actually, it was a complete accident to discover this'Underwater Dragon Palace' at the time, because we didn't know what was underwater before we got into the water." When Cui Yong dived into the water, he found a neat row of stone ladders, and he went down the stone ladders. Dive, gradually approaching the bottom of the hole.
Under the searchlight, an ancient quarry site appeared in front of him.
"The scale of this quarry is huge. Just a hole is the size of several football fields. The big hole is connected to the small hole and it is intricate." There are traces of chisels and other iron tools on the rock walls around the cave.
The deeper Cui Yong was, the more shocked by the sight in front of him: a compartment of the underwater quarry, larger than a few football fields, a vertical quarry wall extending underwater; production area, living area and multiple The small caves are scattered.
It took about half an hour, and the diving watch Cui Yong carried with him showed a depth of more than 30 meters.
Diving to the bottom of the cave and looking up, the entire cave is 10 stories high, and there are some thick wooden sticks inserted on the walls of the cave at different heights. Cui Yong speculates that this should be used by ancient craftsmen to build a shelf. "Scaffolding".
Cui Yong told reporters that because the cave structure is complex and changeable, there are higher requirements for divers' breathing methods, underwater movements, and diving equipment.
On the first dive, he stayed underwater for about an hour.
Carrying two bottles of compressed air weighing about 100 kilograms, Cui Yong was struggling little by little toward the unknown deep water area, and Cui Yong was both nervous and excited.
And this first diving expedition made Cui Yong overjoyed.
He did not expect that there was a cave hidden under the gloomy cave of Shi Yanyan. The vertical depth from the water surface reached more than 30 meters, which could accommodate hundreds of people to work at the same time. It was obviously not a natural cave.
"In the beginning, I tried to draw a map of the cave by hand. Later, I found that the main cave is connected to the branch cave, which is too difficult, so I gave up hand drawing."
"Cave dwelling" a few months a year
Since Cui Yong discovered that there is a large-scale quarry under Shiyanyan, the Shiyanyan cave has become famous, and many diving enthusiasts from all over the world have come here for cave diving.
Shiyanyan has become a famous scenic spot in Xiqiao Mountain. The exposed geological landscapes such as stone ancestral halls, stone screens, stone skylights, and Yixiantian on the ground are of great ornamental value.
From 2006 to the present, Cui Yong's underwater archaeology of Xiqiao Mountain Shiyanyan has been intermittently experienced for 15 years.
Every year, he will "burrow" in the cave for several months.
"We ate breakfast and dinner at the residence on the mountain. We settled our lunch in the cave. Sometimes we set up a bed at the entrance of the cave and slept in it." Depending on the depth of the dive, his stay underwater varies from 1 hour to 3 hours. Wait, every time you descend to a depth of less than 18 meters, you must wait at least 6 hours before you can re-launch.
"In this way, the nitrogen in the blood can be exhausted, otherwise you will get diving sickness and even life-threatening."
Cui Yong's underwater exploration of Shiyanyan caves is generally carried out in winter, because the temperature is low in winter, you can wear a sweater in your diving suit to prevent the temperature from losing temperature.
Because the sky is not visible all year round in the cave, the water temperature is very low, only about 12 degrees Celsius. Even in summer, it feels bitter to enter the water.
Is this cave dug manually or is it a natural cave?
Could this cave be formed by the mining of a natural cave by the miners?
How could this huge quarry be submerged by water?
For these mysteries, Cui Yong finally has the answer through years of underwater archaeology.
"Why didn't the quarrying workers take away the stone that they worked so hard to collect? The only explanation is that there was an accident. When they quarried the stone, they pierced an underground spring, and water sprayed up in a short period of time, which quickly flooded the hole."
Cui Yong said that as an ancient volcano, Xiqiao Mountain has a Tianhu Lake above and an underground river below. It is not surprising that the miners opened up the underground river when mining stones and formed the current water cave.
"You can imagine that the mine was instantly flooded by the spewing water, and the miners stepped on scaffolding or stone steps to escape, and the quarry was abandoned and became a dusty memory, waiting for future generations to solve the mystery."
Uncovering the scene of homework 800 years ago
In order to find out the ins and outs of this "underwater dragon palace", Cui Yong not only dived underwater, but also visited relevant scholars and experts.
"In the entire Pearl River Delta, there is only an ancient volcano like Xiqiao Mountain. This type of stone is only found in Xiqiao Mountain. For example, the platform of Guangxiao Temple, the stone lion, and the ancient city wall of Zhaoqing use this kind of trachy rock. It is very different from red sandstone." Cui Yong discovered through research that the earliest mining year of this underground quarry was in the Song Dynasty, more than 800 years ago, and the large-scale mining was in the Ming and Qing Dynasties.
Beginning in 2015, Cui Yong once again intensively dived into Shiyanyan underwater for archaeology.
Since then, his underwater archaeology has become more targeted.
He said that the Shiyanyan site is the only existing underwater industrial site project in my country, and it is also an outstanding representative of the Lingnan characteristic archaeological project.
On the one hand, he wants to figure out what the life and operation scenes of the quarry workers in the Pearl River Delta were like more than 800 years ago. On the other hand, he wants to verify some unprecedented new underwater archaeological technologies in this large-scale underwater archaeology project.
That time, he dived into the deepest depth of more than 40 meters.
"There are many chisel marks left by ancient workers on the walls of the cave. Mining marks and passages can be seen underwater. The semi-finished stone slabs that have been collected and cut are still neatly stacked. Two copper lampstands, porcelain bowls, and bamboo ladders. Daily necessities such as water and buckets are scattered on the bottom of the water, and there is a layer of floating mud about 10 centimeters thick at the bottom." Cui Yong said while showing the reporter the pictures of the underwater inspection of the Shiyanyan site. His thoughts seemed to be back again. The time to swim in the colorful underwater world.
At more than 40 meters in the deepest part of the water, despite the advanced lighting equipment, it is still black and black, which makes Cui Yong excited but also a little scared of the unknown.
The excavated traces on the cave wall are clearly visible, and different quarrying methods can even be distinguished. Hundreds of collected and cut stones are neatly stacked in a cave similar to a warehouse, and they have not had time to be transported away.
He also found a small furnace made of stone, which was smoked in darkness. Cui Yong speculated that this was used for quenching when the workers made iron tools for digging stones in it.
In this way, a scene of miners quarrying from the Song Dynasty to the Ming and Qing Dynasties seemed to appear in front of Cui Yong.
There are obvious traces of artificial quarrying in the site, and there are supporting pillars left by the mining of stone. All these indicate that the initial stage is mostly open-pit mining. As the scale of mining becomes larger and larger, it gradually develops into cave mining, with inclined shaft excavation and quarrying. .
At the foot of Xiqiao Mountain, the Xijiang and Beijiang rivers flow in parallel, and the stone is transported to the whole of Guangdong and even the whole country by waterway.
"The largest underwater industrial site in China"
In the past ten years, Cui Yong has dived dozens of times in Shiyanyan. He found that the water volume and depth in the entire cave have hardly changed.
Regardless of winter and summer, the error of the water level in the cave is always kept within a few centimeters, and the flow of water is hardly felt in the depth of the water cave.
In addition, Cui Yong has been observing whether there are aquatic plants and plants in the cave, but the answer is no.
He said that some caves are underground rivers, and nourishment can be brought in, so there are fish in them.
However, the water in the Shiyanyan underground lake is immobile, and there is no nutrient supply.
The formation of this unique landscape requires several conditions: first, it is an inner cave without direct sunlight; second, because of the unique topography of Shiyanyan, the water in the cave does not exchange with rainwater, and rainwater will not enter the cave; third , The water source penetrates through the cracks in the stone and is fully filtered, so the visibility is high; fourth, the water temperature is very low, which is not suitable for the growth of plankton.
All of the above conditions have been met, and the Shiyanyan underground cave has the conditions for underwater archaeology.
"It can be said that this cave is a gift from heaven to our underwater archaeologists." Cui Yong introduced that this underwater quarry site is the largest and most complete underwater ancient human industrial relics discovered in China so far, with a total area of the cave. It may reach millions of square meters.
Its age continued from the Song Dynasty to the Qing Dynasty, and preserved the complete traces of ancient quarrying.
Especially the part submerged by the water body has no signs of weathering. It is an extremely rare ancient mining and metallurgical site, with important historical, humanistic and cultural value. It is also a rare underwater archaeological site, which is important for the construction and new technology of underwater archaeology. The application has an important reference and demonstration effect.
Driven by archaeological experts represented by Cui Yong, in 2019, the site was announced as a national key cultural relics protection unit.
Cui Yong's hanging heart finally let go.
"Become a national security unit, the protection will be much greater, at least there is no need to worry about being destroyed."
Looking forward to becoming a world heritage
Cui Yong will retire next year, but he still has no intention of stopping.
"Underwater archaeology is about slow work and meticulous work. I can't rush." Cui Yong said, although he is about to retire, the underwater archaeology of Shi Yanyan has just begun. His goal is to find out each cave first. "Family property", and then in-depth exploration of the cultural relics in each cave.
Cui Yong has always had a desire to extend the underwater archaeological technology formed in the underwater exploration of the Shiyanyan site to other underwater archaeological projects.
Cui Yong introduced that Guangdong has always been a leader in underwater archaeology across the country.
The survey of Shiyanyan Rock in Xiqiao Mountain includes water and underwater. What is different from the usual surveying and mapping objects is that he treats the site of the Shiyanyan quarry as a group of buildings, because the pools, gates, steps, and passages left behind from the mine Structural analysis, such as partition walls, has architectural attributes, but is only a subtractive building; unlike additive buildings with clear external margins, traditional methods of internal surveying and mapping for subtractive buildings can only represent a specific two-dimensional plane, which is difficult Representing three-dimensional three-dimensional, so it poses a difficult problem for surveying and mapping.
With the continuous expansion of the field of surveying and mapping technology and the requirements of archaeological excavations for measurement accuracy, spatial data acquisition methods have gradually shifted from traditional coordinate measuring instruments such as total stations and cross-section instruments to overall spatial data acquisition equipment, such as rack-mounted laser scanning. Instrument, aviation radar, structured light scanner, etc.
Compared with traditional measurement technology, spatial data collection technology has great advantages, especially in data collection, it has the characteristics of high efficiency, speed, accuracy, simplicity, etc., and has been widely used in the field of cultural relics and archaeology.
Underwater archaeology and field archaeology have the same development law of surveying and mapping, from traditional surveying and mapping to high-definition digital surveying. However, due to the large difference in media between air and water, the difference in technology and equipment is also very obvious.
For example, the point cloud data generated by laser static scanning on the land is light wave data, while the underwater 3D imaging sonar point cloud data is sound wave data. Because the Xiqiaoshan Shiyanyan site has dual attributes of land and underwater, it uses different The point cloud data coordinate system obtained by the two methods is not unified. The two methods must be converted to a format that can be opened with the same software, and then manually spliced by the software.
This data fusion technology finally unifies the water and underwater point cloud data coordinates, and completes the complete splicing of Shi Yanyan's water and underwater laser point cloud and sonar point cloud data under the same coordinate system.
The research and development and practice of Shi Yanyan's underwater archaeological data fusion technology laid the foundation for the next large-scale surveying and mapping, provided a scientific and complete technical route, and accumulated experience for the construction and development of underwater archaeology.
To this end, Cui Yong also applied for two national patents for this underwater archaeological technology.
"This set of underwater archaeological surveying and mapping data fusion technology can be regarded as one of my contributions to the construction of China's underwater archaeology discipline in the past 15 years. This technology can be used in future underwater archaeological projects." Cui Yong said with a smile.
For other underwater archaeological projects in the world, Cui Yong has long been familiar with it.
He said that Xiqiao Mountain Shiyanyan Underwater Site can be developed into an underwater museum when conditions are ripe, allowing visitors to have an immersive experience.
"For example, tourists experience underwater how the miners dig and live in the cave hundreds of years ago, and transport the stone out of the cave. I believe this underwater museum with the theme of an industrial site will be very popular." Also because The Shiyanyan underground cave has a high industrial heritage value and can be declared as a World Heritage Site in the future.
Cui Yong also looked forward to that day.