Department of Mineral Resources

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DMR Information

Tham Luang-Khun Nam Nang Non

11 Jan 2021
Inside the cave

To develop the Tham Luang for tourism, it should consider its characteristic in various fields. The basic of geohazard risk assessment is needed including the sensitive area assessment. This information is used to define the boundary of management area in the future in order to ensure the most cost-effective and beneficial under the conservation. The detail of outstanding characteristics of the cave which are obtained by the survey as follow

(1) Outstanding characteristics

Apart from the 12 young footballers and the coach of Wild Boar Football Academy who trapped in the cave during late June - early July 2018, Tham Luang cave also has the interested physical characters which are

  • Entrance with bended stalactite

The numerous of bended stalactite are found at the cave's main entrance chamber which makes it outstanding and has the unique character. When the light shines through the cave in the afternoon, a beam phenomenon will be occurred.

Photo 4.18 The unique character of the cave's main entrance chamber as a signature
Photo 4.19 Bended stalactite at the cave's main entrance chamber

Normally, the stalactite is found hanging from the ceiling in the vertical. In this cave the bended stalactite hangs from the roof following the light because of the growth of photosynthetic bacteria, green moss, and algae. Consequently, the unique bended stalactite makes this cave different from others.

  • Speleothem

The term of speleothem is delivered from “spelaion” and “therma” which means cave and deposit, respectively. It is the form of calcium carbonate or other minerals which deposited in the cave by dripping water or thin layer water. It is mostly found at the ceiling, wall, and floor of the cave such as stalactites, stalagmites, flowstone, pillar stone, bacon formation, rimstone pool, and so on.

Photo 4.20 The speleothem in Tham Luang cave
  • The connection of the main cave

The cave entrance chamber is connected to the main cave which is narrow and full of sharp stone and gravel. The main consists of a small chamber and a large chamber and the gravel is commonly found. The route is difficult to access and dangerous for the tourism. The cave is located in the deep underground which passes under the road heading to Tham Luang-Khun Nam Nang Non national park (preparing). It is expected that the cave can be connected to another cave "Tham Sai Thong".

Tham Luang cave is formed by the limestone which is inserted by igneous rock and pushes the crust upwards as shown in the present. Consequently, the rock is mostly transformed to marble. The earth's crust is constantly moving and the area need to change and adjust in to the equilibrium. Thus, the faulting structures and joints occur in 2 main directions which are north-south and east-west. The geography is later developed in the form of karst and cave as the present-day geography.

Photo 4.21 The entrance to the large chamber in the main cave and the crater at the front of Tham Luang cave.
(2) The risk and sensitivity in the area

The zoning of the cave area needs to consider the risk and sensitivity of the area. It will be useful for zoning and setting the spatial management guidelines in order to develop the area as a tourist attraction. The detail is described as follow

  • Risk

The important factor is used to consider for zoning the cave consisting of rockslide, sinkhole, ravine, flood, thick layer of sand sediment, and so on.

  • Rockslide and landslide

Tham Luang is a marble cave and sharp. It is geologically crack to be the large pieces of marble (Photo 4.22). Actually, the main chamber was large but the entrance is blocked by the large pieces of marble resulting the ceiling is lower and more narrow. In addition, it is found the rockslide and the large rock in the cave (Photo 4.23). The ancient rockslide and landslide are found at both side of the large chamber which is located at the cave's entrance (Photo 4.24).

Photo 4.22 The sharp marble is dangerous for the tourist.
Photo 4.23 The rockslide in the cave resulting the low ceiling and narrow access
Photo 4.24 The landslide at both side of the large chamber, the ancient rockslide at the cave’s entrance (upper row) and nearby landslide (lower row)
  • Tumbled rock

The tumbled rock is found in the cave chamber. It is stuck at the ledge and possible to fall to the floor. The walkway in the narrow chamber needs to manage the tumbled rock or avoid to get close in this area (Photo 4.25). Additionally, the flowstone and stalactite are found falling from the ceiling and wall of the cave as well.

Photo 4.25 The tumbled rock is stuck at the ledge in the cave
Photo 4.26 The flowstone falling from the cave's ceiling.
  • Sinkhole

The sinkhole is not found often because the most area is covered by the sand sediment and the thick layer of gravel. However, it can be found the sinkhole on the mound of the ledge at the right hand side of the entrance chamber which leads to the speleothem chamber in another level. It is near the ancient rockslide and landslide (Photo 4.27).

Photo 4.27 sinkhole on the mound near the ancient rockslide
Photo 4.28 The steep slope and slip in the rainy season, and ravine at the connection of chamber No.3
  • Ravine and slope

Next to chamber No.2 (A34-A36), chamber No.3 is the very dangerous area due to the ravine and slope (photo 4.28). Especially in the rainy season, the water flow in to the cave system from the roof and watercourse. Once the running water combines with clay on the cave's floor, rock, and the speleothem result in the floor is more slip than normal. So, it is not recommended to open this chamber for the tourism.

  • Sand sediment and gravel

The cave's floor is covered by the thick layer of sediment. it fills the space between rockslide and chamber. The sand sediment changes with the season causing the way is blocked and closed, narrowed, or changed (Photo 4.29).

Photo 4.29 sand mounds and gravel, the high mounds almost reach the ceiling in some part.
  • Flood

Tham Luang is the flooded cave. Especially in rainy season at the junction, water flow in to the cave system for a whole year. The high volume of water flow in to the cave and causes flood in different level depending on the physical characteristic and height.

From the remaining trace of clay and water stains, it shows that the water level reach to the ceiling. Moreover, the drinking water bottle is found at the space of the 4 meters height ceiling. It is notice that the bottle flows with running water. That means the water level is higher than ceiling height (Photo 4.30). So, the cave should be closed suddenly when the rainy season or heavy rain.

Flooded water and sand sediment flow in to the cave. It does not only result in the cave chamber change but also cause the stop growing of the speleothem such as stalactite, flowstone, and stalagmite. Apart from that, sediment will coat on the surface of the speleothem and its color turns to brown or rough black. Therefore, it reduces the beauty of cave (Photo 4.31).

Photo 4.30 Flood stain on the cave wall and the low ceiling
Photo 4.31 Sand and clay sediment coating on the cave wall and speleothem
From the survey, the water source that running into the Tham Luang cave as follow

1) Flooded water from rain It occurs in the rainy season during May-September and may skip in some period. Flooded water flows rapidly. Sand sediment and river gravel move together with the running water. Some point in the cave that is narrow and slope, the gravel inside the cave will flow with the running water.

2) Water from the cave ceiling This water source takes a time to move from the roof to the ceiling following the crack, hole, and space. The sediment of stalagmite, stalactite, and speleothem accumulate and coat on the cave wall (sparkling white clear crystals). The survey shows that the frequency of the water drop from the cave's ceiling is high in January 2020 and gradually reduces in the next month.

3) Groundwater in the cave system The water system in the cave and the cave system directly effect on the environment inside the cave such as temperature, humidity, carbon dioxide, and so on. The physical characteristic of the each cave is different resulting in the different environment. It is necessary for the cave that is developing to be a tourist attraction. It has to monitor the environment inside the cave systemically covering all season. This information will be used to analyze the number of tourist and the suitable period for safety tourism. Moreover, it can be used to plan the cave conservation (including the beautiful speleothem) in order to maintain the valued resources.

From the survey, it can be classified Tham Luang into 3 types which are

1) Dry cave or dead cave This type is found at the upper chamber that is near the main chamber of the cave entrance. It is located in higher level from others. The numerous of stalactites, stalagmites, flowstone, and pillar stone exist in this chamber. The area is generally dry. A few number of new accumulate of speleothem is found (Photo 4.32). In addition, collapsed hole is also found nearby.

Photo 4.32 Speleothem in dry whether cave
Photo 4.33 The crystallize of calcite in Tham Luang cave

2) Semi-dead cave The new accumulate and growth of speleothem is found in some area of this cave (Its beauty is not outstanding). The accumulative of stalagmite, stalactite, rimstone Pool are found at the area above flood level (Photo 4.33) such as the area near the command chamber. No any new stalagmite is accumulated at the lower area due to the flooded water in every year. Moreover, the running water contains the large amount of sediment. The sediment coat or cover the stalagmite causing stop its growth and get the damage.

3) Flooded cave At pass the junction, the water flows into the cave system continuously. Consequently, the water flow in the cave for a whole year. For the cave's entrance before the junction, the flooded water occurs seasonally depend on the water volume (Photo 4.34).

Photo 4.34 The water flow in to the cave system at the junction on April 2019
  • Sensitive area
  • Weather

Rain and water in the cave system directly effect on the environment inside the cave such as temperature, humidity, carbon dioxide, and so on. The physical characteristic of the each cave is different resulting in the different environment. The length from the cave entrance to the main chamber is long. If there is no window or chimney connected to outside properly, it will be effect on the air flow inside the cave. So, it is necessary to study and monitor the behavior together with analyze the weather pattern inside the cave systemically covering the enough time. Especially, for the cave that is developing to be a tourist attraction. The collected information is used to analyze for the number of tourist, period, and suitable scope for safety tourism. Moreover, it can be used to plan the cave conservation (including the beautiful speleothem) in order to maintain the valued resources.

The general condition of the Tham Luang is a very long and complex cave (Found chimneys and holes). The level of the cave floor is not stable. The ravine is found in some area. There is some large rockslide in the cave result in narrow and low in various chamber caves. Tham Luang is a flooded cave. So, the accessibility is difficult and take a long time. Apart from that, the water flows with the sediment into the cave in the flood season resulting in the accumulative of sand sediment and gravel. It blocks and covers the walk way. In heavy flood period occurs the soil erosion causing the cave condition changes every year. Now Tham Luang cave does not open for the tourism inside the cave. The tourist can see and take a photo only at the cave entrance. For the other usage of the cave such as survey and field study needs to get the permission from the Tham Luang-Khn Nam Nang Non Forest Park case by case.

On the survey period, the large light bulb was installed for 2 stations at the center of the main chamber and along the walkway heading to the chamber No.1 (command chamber). In late January 2020, the large light bulb was moved but the light along the walkway is still operated (Photo 4.35).

Photo 4.35 The light bulb which is the heat source directly effect on the cave system

The monitoring of environment condition in the cave consists of carbon dioxide, temperature, and humidity which were collected every 30 minutes per day. The equipment for carbon dioxide monitoring was installed at the chamber No.2 (A35). The data was recorded automatically. The survey period is 5 times which are.

  • 15-16 January 2020
  • 14-15 February 2020
  • 12-13 March 2020
  • 24-25 May 2020
  • 29-30 May 2020
Photo 4.40 The sensitive area between A8 and A9 a) Rimstone Pool b) Soda straw
  • Risky damage area

The survey found that the sensitive area is the risky damage area. The rimstone pool is found at the area between A8 and A9 on the left hand side of the stair heading to the command chamber. It is the lime sediment and form as the dam or barrage. In addition, the soda straw is found above the rimstone pool which is formed by the water drop from the ceiling cave and the carbonate accumulates in vertical. Its shape looks like the straw with the space inside the rod and water drop at the end (Photo 4.40). The stalactite and bacon formation are found at the A34 which can be cracked easily and found the piece of sharp stone nearby. It may be cracked by touching and reduce its beauty. The rimstone pool, soda straw, stalactite and bacon formation are categorized as the fragile speleothem, easy to damage, and take a time for the restoration.

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