At this point in modern technology, it seems as though every possible frontier out there has been explored. We’ve even been to the moon! So things like vast, uncharted underground caves like the Mulu Caves in Borneo, Malaysia are especially rare and significant to scientists and nature lovers alike.
The Mulu Caves are a part of the Gunung Mulu National Park in Miri Division, Sarawak, Malaysia and are thought to contain both the biggest cave and largest cave passage in the world. Clearwater Cave is believed to be the biggest cave, with the average passage diameter coming in at 16 miles across (as of May 2014 it’s also believed to be the 8th longest cave in the world). Deer Cave, on the other hand, is 174 miles wide and 122 miles high at some points.
It was over 5 million years ago when the first Mulu caves began forming. First, limestone and sandstone mountains began forming side by side due to sideways earth movements. After millions of years of heavy rain, the running water and flow of rivers began carving out the subterranean cave system that we know today. It’s a process that continues, albeit slowly, to this day. Dripping water slowly erodes limestone so that new crevices and caves are being carved out.
The first known reference to the Mulu Caves dates back to 1858, when Spenser St. John wrote about “detached masses of limestone, much water-worn, with caverns and natural tunnels” in his book Life in the Forests of the Far East. It wasn’t until just over 100 years later, in 1961, when G.E. Willard of the Malaysian Geological Survey went to the National Park specifically to visit the caves.
The most famous and fruitful expedition has to be the Royal Geographical Society Expedition which went from 1977-1978 and brought over 100 scientists to the caves to do important and groundbreaking research for over 15 months.
It was during this time that Clearwater Cave was discovered and Wonder Cave, Prediction Cave, Deer Water Cave, Mayday Cave and Bat Cave were surveyed. During this time, there was no nearby airport nor any real roads to get to the caves so the scientists had to set up base camp at Long Pala which was a 3 day journey upriver in a canoe. This first step of exploration facilitated 20 more journeys into the caves, collectively called the Mulu Cave Project.
In 2014, researchers made an incredible discovery of new levels in the Clearwater Cave system, giving it the potential to be even bigger than previously thought. The intrepid cavers reached new heights previously unexplored due to the difficulty of the terrain and remoteness of the location.
The most recent expedition, in 2015, was the 23rd Expedition and focused on three separate objectives. The first was based in the Hidden Valley area to find new entrances that the explorers saw on previous helicopter footage. The second group was in the Melinau gorge while the third spent time with a 3D laser to scan the geomorphology of some of the cave’s chambers.
While there have been extensive expeditions conducted throughout the Mulu caves since the 77 Royal Geographical Society Expedition, scientists think they’ve only surveyed between 30-40% of what’s there.
Mulu Caves are a popular tourist attraction; their grand and overwhelming size and mysterious unknown depths spark the imagination of visitors of all ages. While it may not have had modern amenities like an airport back in the 70s, today the area has an airport, ferries, resorts, restaurants and cafes. There are a number of guided tours visitors can take, including more intense caving expeditions for experienced cavers and more accessible trips for the novices.