PRELIMINARY REPORT
The expedition was very successful, with some extremely interesting and important cave science, some more exploration of gigantic caves and a complete laser scan of one of the largest cave passages in the world.
During the 2022 expedition there were over 42 separate survey trips. From this 6.5 km of newly discovered cave was surveyed. Much of this was done using underground camps within the Clearwater system, utilising the Snake Track entrance.
Main discoveries
Blackrock
Based out of a camp in Sheer Delight passage, a ~50m high aven was climbed in No Justice, near to the Blackrock Clearwater connection point. This led into 250m of large horizontal passage heading SW before beginning a 300m vertical ascent of surely one of the longest ramp series in the system. Despite an encouraging draft this “Sandstorm” series ended at a terminal blockage and an undescended pitch at a maximum elevation of 473m.
Scumring / Creedence area
Three camps were held at Scumring to explore various leads identified from previous expeditions. The most significant discovery was at the northern most end of the Scumring Series, down a previously undescended pitch. This dropped into Serve Cool Houblon, a slowly ascending passage of excellent style and proportions. After 500m it arrived at the bottom of a 30m undescended pitch from the higher Upskirt Level, thereby ticking off that lead too.
Later a 10m bolt climb from the Lower Upskirt level led into a 100m high ramp series where over 500m of passage was surveyed. Similarly a short pitch was descended in Gin Palace, off the Creedence Level, to enter another ramp this time spanning a 140m vertical range. The top of this ramp marks the second highest known place in the Clearwater system at an altitude of 525m.
Whilst mediocre in proportions, these ramps provide excellent information on the steep bedding of the limestone and may offer a rare glance into the complex formation of these high level passages.
Easter Cave
A camp was established in the high level passages of Easter Cave which was used extensively throughout the expedition to continue exploring this relatively newly found cave and looking for a connection down into Lagangs below. In total 672m of new cave was discovered and surveyed, including sections that get close to Sago Palm Cave directly above and Pass Go, which heads due East and travels directly over the main Lagangs passage.
Likewise, attempts to find a connection from Lagangs resulted in the discovery of 605m of new cave in 6 different areas, most very close to the showcave path. Unfortunately, the hoped for connection to Lagangs Cave was not accomplished, this time.
Racer Connection
Cave of the Winds was successfully connected to Racer Cave via a 15 meter cave dive. This alone added 11.9 km to the total length of the Clearwater system.
With all these new passages and the dived connection, Clearwater is now 256 km long – moving up the world’s longest cave ranking from 9th longest in the world to 8th longest in the world, overtaking Lechuguilla cave in the United States.
In addition, another 4.2 km of cave passage was re-surveyed to increase the accuracy of the underground survey and to help with the scientific interpretation. This work forms part of a large resurvey project, and as per other expeditions, has led to the almost accidental discovery of new cave, this time in the Dr Fu Yens Mystical Earthly Paradise area and also in the Volcano Series.
The cave surveying was supplemented with the laser scanning in total over 4.0 km of gigantic passages was recorded. This will enable the team to make a digital 3D model, which can be used in many ways, from flying a small digital aeroplane through the digital cave, to studying the detail of the cave passage to help towards the scientific interpretations. In total, over 10 days were spent simply completing this 3D laser scanning traverse and it is hoped more will be done in the future.
In addition to the normal photography, survey and detailed recording of the caves, an ambitious science programme was led by Dr Andrew Farrant and Dr Hazel Barton:-
Mulu Caves 22 Science Report
Dr Andrew Farrant & Dr Hazel Barton
The scientific objective of the Mulu Caves 2022 expedition was to assess the evidence for continued modification and enlargement of tropical caves, what drives this enlargement, and whether this is due to geological or biological processes. Previous expeditions to Mulu had identified features in the caves that suggested that dissolution either from the condensation of moisture in the air on surfaces or from acids leaching from guano continued to enlarge the caves, long after the passages had been abandoned by the formative river.
Several methods were employed to examine whether such dissolution was actively taking place and identify the potential mechanisms. The first was simple observation of the cave passages for evidence of subaerial dissolution, such as corroded walls and stalagmites, corrosion pitting, guano crusts and anomalous scallops. We also collected samples of water from the caves, in particular water condensing on the passage walls, drip waters entering from the roof, and water condensate collected on ice bottles left in the caves. We measured the pH, temperature and conductivity of these samples and tested their chemistry using water testing kits. More detailed analysis of the guano was also undertaken to identify what geochemical and microbial processes may be contributing to dissolution, and whether these activities are impacting the ropes and packs used in the caves. To look at longer term erosion rates, small accurately weighed limestone tablets were left in the cave. These will be left in the caves for 1-2 years to see how much they dissolve. The tablets were placed in variety of settings, on cave floor, on mud/guano, within guano, in drip pockets and suspended in the air. Due to the requirement for advanced testing, this work is ongoing.
Our initial field results suggest that there is significant dissolution occurring in many of the Mulu caves, even where the cave passage is dry. Passages close to the modern base level show typical features formed by flowing water, for example in the Clearwater show-cave, the low-level notch just above river level has good dissolution flow marking (scallops). But in the upper notch, about 20 m higher and well above the current level of the river, these scallops are absent. This suggests a process leading to their dissolution, which would indicate several cm of wall-rock retreat since this level was abandoned by the river within the past 100,000 years. In the much older, higher passages, such as Revival in Clearwater and in Stone Horse Cave, the rock walls show more evidence of being sculpted by moist air rather than water. Likewise, some stalagmites have been corroded to reveal their internal growth banding. In some cases, stalagmites over a metre thick have been dissolved to reveal the underlying rock.
The water samples identified a significant difference between drip waters from stalagmites and atmospheric condensate, which are nitrate free, and condensate and drips collected from the cave wall, which are high in nitrate. Our preliminary data suggest that the guano in the caves, from the nitrogen-rich diet of insectivorous bats and swiftlets is a key part of a previously undescribed cave forming process. Microbial degradation of the guano has previously been shown to produce ammonia, which is consistent with our field data. Ammonia is highly soluble in water, such as the moist air of the cave. This ammonia-rich water likely condenses on the cave walls or mixed with slow percolation water entering the caves, whereupon the ammonia is an important source of energy for microbial growth, where it is converted to NOx, which is a strong acid. This conversion may therefore lead to the formation of highly aggressive water on rock surfaces, accelerating limestone dissolution and resulting in the nitrate-rich water detected on these surfaces. This process would be most active in areas with large guano deposits, coupled with a good draught and a lot of moisture. In these areas, sufficient dissolution to remove the original scalloping can occur within a few tens of thousands of years. In the older higher-level caves, tens of cm to possibly metres of wall-rock retreat may occur. In short, the evolution of the Mulu caves is an active and ongoing process, driven by what appears to be an intimate association between the landscape, its animals, and the caves.