Trapped in flooded caves

From June into July of 2018, media coverage about 12 boys and an adult man trapped in a cave in Thailand transfixed people around the world. The incident provides an opportunity to discuss spooky geology related to caves and karst hydrogeology.

Thirteen trapped in Tham Luang cave – Summer 2018

Originally written in June 2018.

From the news reports, we heard that 12 boys on a soccer (football) team entered the Tham Luang cave complex with their coach after a team practice on June 23 and did not come out. Tham Luang Nang Non (Great Cave of the Sleeping Lady), located in Chiang Rai province in northern Thailand, is a network of caverns and connected passageways estimated to be 6 miles long but is poorly mapped. The group went exploring in the underground openings, as they had done before, crawling through tight spaces in some places only about the width of their bodies and possibly wading through water. Officials spotted their belongings outside the cave after parents reported the kids missing and it was assumed that the recent rainfall caused the cave system to flood very rapidly, trapping the group inside.

According to the timeline from the South China Post, on June 25 rescuers made their first efforts in the cave, hoping that the group made it to an elevated dry area far inside. Heavy water inflows prevented the divers from getting far. Continued rain means the passageways remain flooded. The rescue operations then ramped up with teams and equipment arriving on site from around the world to assist. Pipes and pumps are installed in an attempt to control the water levels. 10 days later, on July 2, the group is discovered by two experienced British cave rescue divers, Rick Stanton and John Volanthen, in the situation they expected, perched on a spot that remained above the water level 2.3 miles (3.75 km) inside the entrance. The divers had to enlarge a small passage in order to get through with their air tanks which indicates just how narrow some of these channels are.

The group was trapped because of the hydrology of karst areas. The solution-enlarged passageways within the mountainous limestone area form a natural system that collects and transmits water rapidly after rains. Precipitation soaks into the ground, making its way through rock fractures of all sizes. The water moves unimpeded through the underground passages causing a fast rise in groundwater levels and submerging areas that were previously dry. It is well-known to locals that the cave should not be explored during the rainy season, beginning in July, for this reason.

CNN had a visual explanation showing the flooding of the cave complex that trapped the explorers. The system of openings is not level, so some parts remain above the water table.

It should be clear how they can not simply exit just like they entered. They can not swim out as the passages are confined with no access to air spaces, the water is moving fast through the system causing disorienting and dangerous currents to swim against with low visibility due to silt in the waters.

One option is to give the trapped group a crash course in cave diving and practice using the breathing apparatus so that they can individually be guided out. Dive training for cavers typically takes days of practice under less stressful conditions. The kids apparently are not strong swimmers and are weak from lack of food and sleep and the difficult environment underground they have endured for over a week. If the individual can correctly don the equipment, difficulties remain in the long and strenuous trip through rapidly moving water, maneuvering through confined spaces where accidents can occur. Navigating this particular system is challenging for even experienced cave divers. The rescue divers called the trip “gnarly”. Though there is no solid set of statistics for cave fatalities, hundreds of people, including some experienced divers have died while attempting to navigate underwater cave systems around the world.

Men trapped in mining tunnels have been successfully rescued on several occasions through use of technology and engineering where rescuers were able to rapidly drill large holes in precise locations to lower rescue pods. This option does not appear viable here. The region is mountainous and the underground system is not precisely mapped such as with a man-made tunnel. The odds that a half-mile long rescue hole would hit the mark is extremely low. Attempts to find another way into the system are continuing but so far has not been successful. The kids reported hearing outside noises suggesting another passageway exists to the surface but it’s not clear if these were real sounds, misinterpreted, or hallucinations.

Additional heavy rain is anticipated in the coming week. Fortunately, the cave air and water is warm so hypothermia is not an imminent problem. Pumping water from the caverns continues, but because the surface drainage area to the system is so vast, even a huge pumping operation may not be enough to control the inflow from continued rains let alone lower the water levels to facilitate a rescue attempt. Water that normally flows into the cave system has also been diverted. Dozens of farm fields have been flooded from the discharge but the landowners are happy to oblige in the rescue attempt. Additional technological options are being considered as experts and corporations offer their assistance. If the weather remains dry for a few days, exit plans may become less perilous. Do officials wait and hope this occurs, which could mean weeks or even months of waiting while sustaining the trapped group with supplies, or do they move ahead with the tricky and risky efforts to swim out?

With this agonizing and treacherous situation, we see another example of how geology can both fascinate and frighten us. The group was drawn to explore the unfamiliar and challenging environment of this cave system and now they face the consequences of the inconspicuous factors that led to their entrapment and a life-threatening plan of escape.

Rescue

All 13 were rescued over a three-day span. Using a window where the water levels were lowered, divers guided out each individual by using extra oxygen tanks along the route. The successful mission was darkened by the death of one Thai Navy SEAL diver who was helping to set up the rescue attempt. He apparently ran out of oxygen. The lack of oxygen in the cave space indicated that there was not an alternative shaft to the cave from the outside and the only immediate way out was through the flooded passageways through which they entered. Accounts reveal that by the third day, experience with the route had quickened the exit trips. Science and engineering skills were the keys to this rescue. The team had extensive knowledge of cave systems and equipment and were able to use life-saving methods to sustain the trapped group and then maneuver them each out from underground. The Thai government says extra security will be used to guard this now world-famous cave. The group may suffer from Histoplasmosis, a lung disease that results from breathing the humid air in the cave system that contains fungus spores and particles from bat droppings. One might assume their days of cave exploring are forever over.

5 trapped in Krizna cave, Slovenia – January 2024

Heavy rainfall on 6 January 2024 in the area of Krizna tourist cave in southwestern Slovenia, resulted in three adults and two guides being trapped in cold, low-light conditions for 3 days. The rain resulted in the water levels to rise too high for visitors to escape by boat. The cave is water filled and only accessible by boat with guides. The people trapped had been supplied with items by divers as they waited for the waters to recede. All exited the cave in good condition on 8 January. It’s unclear why visitors were allowed if heavy rain was expected. The cave website does note that the long tours may be cancelled 2 days in advance due to heavy rains. Source: AP