February - 2019

The  existence  of  large  caves  in  the  Gunung  Mulu  area  of Northern Sarawak has been documented for over 150 years.

Northern Sarawak

Fig 1; Northern Sarawak

In 1858 reference was made to “Detached masses of limestone, much water-worn, with caverns and natural tunnels” around the base of Mulu by Spenser St. John in his book ‘Life in the Forests of the Far East’, (St. John, 1862). St. John was ‘Consul General in the Great Island of Borneo’  and made some of the earliest exploratory journeys  of  any European into  the interior of Sarawak.  His attempts to reach the summit of Mulu were thwarted by limestone cliffs, dense forest and sharp pinnacles of rock and he says, “It is almost  impossible  to  conceive  the  difficulty  of ascending this mountain”. Mulu was to keep the secrets of its summit for a further 74  years  until  Edward  Shackleton successfully climbed the mountain during the Oxford University Expedition of 1932, (Harrison, 1938).

In 1961 G.E. Wilford, of the Malaysian Geological Survey, visited the area to explore its caves. His work included the surveying of Deer Cave and parts of Cave of the Winds. He predicted that Mulu would yield many more caves in the future, (Wilford, 1964).

During 1977-8 the ‘Royal Geographical Society Mulu Expedition’ spent 15 months in the area studying many aspects of the rainforest. This was the largest scientific expedition ever to leave the UK. Included in the team were six speleologists who, in three months, explored and surveyed 50kms. of cave passages including parts of Clearwater Cave, Green Cave and others, (Brook & Waltham, 1978).

Deer Cave 1980 | photo © Jerry Wooldridge

During the expedition a forest camp was established in Hidden Valley from where two major caves were explored. ‘Prediction Cave’ on the south side of the valey contained enormous passages which were almost filled with river sediments, (Meredith, Wooldridge & Lyon, 1992, p.10). ‘Wonder Cave’ on the north side of the valley was found to have some of the largest passages in Mulu.  It was obvious from these findings that Mulu ranked as one of the world’s foremost caving regions.

As  a  result  of  the  RGS  expedition  two  large  scale  caving expeditions were mounted in the early ‘80s.   The ‘Mulu  ‘80’ expedition explored and surveyed a further 50km of cave passages including the largest underground cavity, in the world, ‘Sarawak  Chamber’,   which     forms the    final chamber of ‘Lubang Nasib Bagus’ or ‘Good   Luck Cave’, (Eavis, 1981). The end of this chamber lies very close to the end of Prediction Cave in Hidden Valley and tantalising draughts at the end of each cave suggested a connection.

In 1984 the ‘Sarawak ‘84’ expedition spent one month in the field and explored 54km of caves. Clearwater Cave was extended by 14km but a great deal of work was carried out in Benarat where Cobweb Cave was discovered, adding a further 15km of passages to the Benarat total.

These two expeditions carried out a great deal of scientific research associated with the caves including dye tracing, geology, geomorphology, ecology, cave mineralogy, etc. However, although 150km of some of the largest caves in the world had been surveyed, some very significant areas of limestone remained totally unexplored presenting enormous potential for further exploration.

Blackrock Cave | photo © Jerry Wooldridge

During late ‘87 and early ‘88 plans were made to mount another caving expedition to the area.  This would be the first expedition to visit the park since its opening to the public in 1985 and was primarily aimed at exploration, surveying and photography. Unlike the previous expeditions this was to be a lightweight venture with only six team members. The ‘Mulu Caves ‘88’ expedition once again proved the potential of Mulu with a further 16km of passages explored. It was also shown that exploration in Mulu using a small team was both feasible and successful.

The major discovery of this expedition was Blackrock Cave lying to the north of Clearwater and almost certainly part of the same system, (Kirby 1989, p.28).

As a direct result of this discovery, an eight strong  group, including five of the 1988 team, returned to the  Park exactly one  year later  as the Mulu Caves ‘89’ expedition. Once again a lightweight venture proved to be successful with over 24km of passages explored and surveyed in only one month.  Major extensions were found in Clearwater Cave totalling 15km and the gap between it and Blackrock Cave was brought to within 90m.  The Clearwater 5 streamway was discovered and explored for over 1km.

A new cave, provisionally named ‘Simon’s Cave’, but later named ‘Racer Cave’, was discovered and explored and water tracing experiments proved a hydrological link from the Melinau Gorge through Blackrock  and  into  Clearwater  Cave,  (Kirby, 1990).  The discoveries made by these two expeditions had greatly altered the map of Gunung Api’s caves.

During 1990 another British team, the ‘Gunung Api Connection’ expedition’, visited the Park and continued the exploration of Racer Cave. The Clearwater 5 streamway was explored to an upstream sump.  Although a sump bypass was found to lead into Clearwater 6, rain caused the bypass to sump which prevented further exploration (Weight, 1990). A physical link    was    established between Drunken Forest   Cave   and   Alexandra Palace in Clearwater.

During February 1991 a Korean Team visited the Park. Some minor discoveries were made. Unfortunately these findings were not published.

In 1991 a group of nine explorers, five of whom were from the ‘88 and ‘89 expeditions, returned to the Park to continue exploration in the Blackrock/Clearwater area. A connecting passage was discovered which linked the two caves. This discovery made the Clearwater System the seventh longest cave in the world at over 102km. This was the ‘Mulu Caves ‘91 expedition.

In 1991 two members of the ‘Gunung Api Connection’ expedition returned to the Park to continue the exploration of Racer Cave. Above Batu Bungan a new cave was explored, named Palm Cave, and Fern Rock Cave was explored in the Southern Hills (Weight, 1991).

A vast amount of work had, by this time, been carried out on the western flanks of Gunung Api and although discoveries were by no means exhausted it was becoming increasingly difficult to find major objectives which would justify another expedition to that side of the mountain.  The remaining significant lead, the Clearwater 6 Streamway, was weather dependent and, therefore, could not be relied on as a sole objective.

Cliffs above Prediction Cave | photo © Matt Kirby

Attention now focused on the more challenging eastern flank of Gunung Api with Hidden Valley as the first objective. This area was less accessible than the west as there were no major rivers which could be used for transport of stores and equipment.

Tentative enquiries were made in 1990 to see whether it would be possible to visit the Valley during the ‘91 expedition.  A positive response was  received and  this became  one  of  the  secondary  aims  of  that  expedition. Unfortunately this was not achieved as other discoveries closer to park headquarters took priority. Instead, part of the ‘91 team returned approximately one year later in January 1993 as the ‘Hidden Valley ‘93’ reconnaissance expedition with the sole objective of carrying out a lightweight reconnaissance of Hidden Valley.

The reconnaissance expedition proved a success with potential for further discoveries to be made in the two known caves within the Valley and a new cave discovered in the dolines to the west. Other entrances were noted for further investigation and surface reconnaissance suggested even greater potential further south in the deeper ‘Third Doline’, which was not entered.

During 1994 members of the Gunung Api Connection expedition returned to the Park as the ‘Caves of Fire Mountain’ expedition. This expedition connected Leopard Cave into the Clearwater System and attempted to connect Cave of the Winds to Lagans Cave. Exploration continued in the Fern Rock/Stone Horse /Fat Frog Cave system in the Southern Hills. Surface searching was also carried out in the Melinau Gorge where a number of entrances were located and explored (Weight, 1994).

With the Hidden Valley reconnaissance expedition indicating potential for further discoveries in Hidden Valley a full exploratory expedition, ‘Mulu Caves 96′, was mounted and returned to the Park in October 1996. A base camp was established within the Hidden Valley gorge between the entrances of Prediction and Wonder Caves. Although very little was found within the main gorge exciting discoveries were made in the dolines to the south west. Arch Cave was explored in the second doline. Prediction and Bridge Caves were found within the third doline and the fourth doline revealed Cloud Cave which matched Deer Cave in scale. During the last few days of the expedition a descending boulder ramp was followed which led into the far reaches of Cobra Cave. This established a through route to the Melinau Paku valley.

During 1997 an American expedition, the ‘Caves of Gunung Buda 1997′ expedition, which was exploring Gunung Buda, carried out surface searching on the northern slopes of Benarat. This led to the discovery of Deliverance Cave on the north east corner of the mountain. 3.5km of passages were explored which were heading in the general direction of Cobweb Cave.

With the success of the ’96 expedition a second Hidden Valley expedition, ‘Mulu Caves 98′, was mounted which returned to the Park in February 1998. As the centre of exploration was to be in the dolines it was known that this would not be best served by a camp within the Hidden Valley gorge. Not only would a camp in Hidden Valley be remote from the caves, it would also be almost impossible to supply without helicopter backup, which would be very expensive and could not be relied upon.

With this in mind, a gamble was taken on being able to reach the 4th Doline from the Melinau Paku Valley via a route, over the surface, which had never been explored. It was thought that the route through the caves would be used only as a back up, however, the severity of the climb up from Nasib Bagus, together with the surface terrain proved to be far more difficult than the underground route via Cobra Cave, which soon became the main thoroughfare.

This expedition proved a great success with further extensions in Perseverance Cave and a connection established between Cloud and Bridge Caves establishing the Cobra – Cloud – Bridge system at 16.1km. with a vertical range of 459m, the greatest vertical range of any cave in the Park.

Owing to the El Nino year river levels were exceptionally low so a further attempt was made to explore beyond the Clearwater 5 upstream sump into Clearwater 6. This led to another sump which was bypassed into Clearwater 7 and the inevitable upstream sump which was not passable. This expedition was the last to visit Hidden Valley.

Another American expedition, the ‘Caves of Gunung Buda 2000′ expedition, visited Buda in 2000 and carried out further work in Deliverance Cave, bringing its total length to 4.3km.

With exploration in Api now without any significant leads attention of the British team was drawn to Gunung Benarat. It had been sixteen years since a British expedition had visited the mountain during the Sarawak ’84 expedition. The ‘Benarat 2000′ expedition continued the exploration of Cobweb Cave where a further 10.7km of passages were explored bringing the total length of the cave to 25.9km.

Camp 5, base camp for six expeditions | photo © Andy Eavis

As a follow up to the 2000 expedition the ‘Benarat 2003′ expedition returned to the park. A further 4.4km were explored in Cobweb Cave but the significant discovery of the expedition was made in Terikan Rising Cave where 12.5km of passages were explored. Included in the team were two Api veterans who were to use the expedition, based at Camp 5, as an opportunity to prospect the northern slopes of Api between the Melinau Gorge and Blackrock’s Racer entrance. This revealed a significant entrance 2.8km south west of Camp 5. The cave was named Whiterock and within the remaining three days of the expedition it had revealed 3.7km of new discoveries. Owing to its proximity to Blackrock it was thought that it would soon connect and might be of little significance.

During 2005 the ‘Benarat 2005′ expedition, based at Camp 5, continued the exploration of Whiterock which exceeded all expectations when a further 17.2km of passages were discovered, mostly lying above Blackrock. Two connections were made between the two caves which linked Whiterock into the Clearwater System.

On the Benarat side of the gorge an attempt to climb up to an entrance high in the cliffs opposite Camp 5 was cut short when a small entrance was discovered only 60m above the ground. This cave was named Moon Cave and was explored for 6.6km in an almost straight line into the mountain. A connection was also established with Benarat Caverns making the total length of this system 16.4km. Included in the expedition were two divers who investigated the sumps in the Terikan system. This proved connections between the individual elements of the system to make a total length of 32.5km. The total length of caves in Benarat was now 90.4km and in Api was 172.6km.

In February of 2007 the ‘Mulu Caves 2007′ expedition visited the Park, once again based at Camp 5. Exploration continued in Whiterock Cave where 21.9km of passages were explored and surveyed, bringing the total length of the cave to 42.9km. Northern discoveries saw passages tantalisingly close to breaking out into the Melinau Gorge, the closest being only 370m from Camp 5. Unfortunately a northern entrance remained elusive.

On the Benarat side of the gorge Moon Cave continued to yeild exciting discoveries with a connection made between it and Cobweb Cave. This now linked together Cobweb, Moon and Benarat Cavern to make the Benarat Caverns System, now 50.5km long, the second longest system in the Park. The expedition also carried out surface survey work on the Api side of the Melinau Gorge to record and link together all the known cave entrances.

During January to March of 2009 the ‘Mulu Caves 2009′ expedition continued to explore Whiterock Cave and discovered a further 24km of passages.

May 2010 saw a small group return to the Park as the ‘Mulu Caves 2010′ expedition. This ‘mini’ expedition was based at Park headquarters to carry out surface survey work and to update the photographic record of the caves within the Southern Hills. The ongoing scientific programme was continued in caves of southern Api and The Deer Cave Massif. Various caves, little visited since the early 80’s, were re-explored and all known caves linked together by extensive surface traverses. Although primary exploration was low on the agenda some new passages were discovered and the length of caves in the Southern Hills was extended to over 20km.

The ‘Mulu Caves 2011′ expedition was in the Park during February and March of that year. This was a two part expedition with the first part based at Park HQ. Deer Cave and Sarawak Chamber were both laser scanned and a new digital image of Sarawak Chamber was achieved. The expedition then headed for Camp 5 to further explore Whiterock Cave which revealed another 13km of passages. In northern Benarat a new cave, Paradise, was discovered which revealed 1.1km of passages.  Although close to Blue Moonlight Bay Cave no connection was made. In total the expedition surveyed 15.1km of new passages and set up a series of accurate GPS fixed points around the Park to better calibrate the dataset.

In 2012 a team returned to explore the Southern Hills area, recce’d by the small 2010 trip, with a further emphasis on scientific work in the large caves close to the park headquarters. A major new cave, Train Cave, was explored high in the difficult terrain between the Hidden Valley and Melinau Paku, which connected to Bridge Cave, extending the length of the Cloud/Cobra/Bridge System.

‘Mulu Caves 2013′ revisited Camp 5 from where it explored further in Whiterock Cave, finding a further 8 kilometres of passages, mainly in the north of the system, although one large lead in the south was discovered on the last day and only partially explored.  Deliverance Cave in northern Benarat was also visited and many avens were climbed hoping to find a route southwards into the heart of Benarat.  Despite much effort this was not to be.  Many expedition members were new to Mulu and the minimal gains of the expedition – 11 kilometres – were no reflection on the young, tough team. Some years are like that, although it suggested that the days of cherry picking big passage are perhaps numbered.

Or are they?  ‘Mulu Caves 2014′ was launched in April/May 2014 to continue the work established by the 2012 exploits in the southern area of the park. The large Easter Cave was quickly discovered which fitted neatly between Racer and Lagangs caves, connecting to the former and nearly connecting to the latter (it must only be a matter of time). Meanwhile Clearwater Cave, which had not been seriously looked at since  1991, revealed some astonishing discoveries – a high level network, Creedence, was climbed into above the Scumring camp area with wide open passage whose exploration was halted after 8 kilometres only due to lack of time. Over 100 leads in this series alone were left for future explorations. These discoveries, high above anything previously known in Clearwater or Whiterock, not only pushed the Clearwater Systerm beyond the 200km length mark, but they opened up a whole new horizon for exploration and growth of the Clearwater System.

The ‘Mulu Caves 2015’ expedition was an ambitious project centered on three locations, Southern Api, Hidden Valley and Camp 5. In Hidden Valley a lightweight recce was carried out to investigate a large entrance identified from helicopter video footage in the north wall of the gorge. This revealed Conviction Cave which connected into Wonder Cave, unfortunately a serious accident curtailed some of the work here. Further exploration was carried out in Racer and Lagangs caves but no connection made. From Camp 5 8065m of new passages were explored in Whiterock Cave where a new level was entered 100m above anything previously discovered. This was 380m above the lowest part of the cave confirming the existence of higher levels within the cave and potential for far more discoveries in the future.

During April 2017 the first of two ‘Mulu Caves 2017’ expeditions visited the park and was based at Park HQ. Further work was carried out in southern Clearwater and in Cave of the Winds where the Eureka series was discovered lying just above the river passage.

The second ‘Mulu Caves 2017′ expedition was based at Camp 5 during October where 4.2km of new passages were explored in Whiterock Cave bringing the total length of the cave to over 100km and the Clearwater System to 226.3km. Within just 15 years Whiterock had become a 100km cave, the longest cave in the Park.

In January of 2018 the ‘Mulu Caves 2018′ expedition visited the Park primarily to carry out experiments on cave draughts. Some work was carried out in the Melinau Gorge to locate cave entrances using a camera drone. A systematic re-surveying of parts of Clearwater Cave was started where the original survey data had been lost.

The next expedition will be in Spring of 2019.