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Monday, 28 August 2017

Mulu Caves 2017

Preliminary Report of the Mulu Caves 2017 Expedition

Summary and results

Mulu Caves 2017 was the 24th Anglo-Sarawak Expedition to Gunung Mulu National Park and operated in the field between 29^th March and 27^th April 2017. The expedition had several components:

1) A team in the Hidden Valley to continue exploration and surveying of new extensions of Wonder Cave, first discovered via the Conviction Cave entrance in 2015.

2) A team to continue exploration and surveying of the high level Creedence series (discovered in 2014) in Clearwater Cave.

3) A team to look for connections in the Southern Peninsula area of Gunung Api, between Cave of the Winds (part of the Clearwater System), Racer Cave and Lagang’s Cave.

4) A team to climb into a potential high level passage in the roof of Sarawak Chamber.

5) Photography of the expedition and Mulu caves by National Geographic.

6) Scientific study of palaeomagnetic sediments and notch elevation surveys.
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In the Hidden Valley, a total 12.5km of new passage was discovered surveyed and photographed over a vertical range of 380m.

In the Clearwater Cave System, 6.8km were added to the surveyed length of the cave system, taking it to a new overall surveyed length of 222km.

1.3km were added to Lagang’s Cave, making it just under 8km total length and 430m were added to Racer Cave, making the total length 6.7km.

A programme of sampling and observational data collection was carried out as part of the ongoing study of the geomorphology and speleogenesis of the Mulu caves.

The team of twenty-eight were led by Andy Eavis and comprised members from the UK, Germany, USA and Belgium plus our hosts at Sarawak Forestry. The expedition was greatly assisted by National Park Management, staff and local people.

Exploration, Surveying and Photography

1) Hidden Valley – Dave Nixon

Since the discovery of Conviction Cave and its subsequent connection to Wonder Cave during the 2015 reconnaissance expedition to the Hidden Valley, a return visit was inevitable. The way into the eastern side of Gunung Api was openly available and totally unexplored.

A team of eight was carefully selected including members of the previous expedition as well as 4 new but suitably skilled members including a Doctor.

The mobilization to the Hidden Valley was executed by helicopter, hired in Miri and flown via Mulu airport, to collect personnel and approximately 500kgs of equipment. These logistics took meticulous planning and luck had its part to play with the weather for the pre-selected flying day.

On arrival at the Hidden Valley a base camp was again constructed at Prediction Cave and radio communications were established by means of a mast erected on the helipad. In addition, a new satellite phone system was successfully employed as an emergency means of contact. The cave was soon rigged up with approximately 500m of rope and anchor points. This meant the team could base themselves at an underground camp close to the limit of the 2015 exploration and then continue their exploration.

Splitting into multiple small teams, the exploration of the Wonder/Conviction system commenced with progress mainly in a northerly direction towards the Melinau Gorge. In total 12.5km of new passage were discovered, surveyed and photographed over a vertical range of 380m. The limit of known cave passages on the east side of Gunung Api now extends 3.3km north of the Hidden Valley and falls short of exiting in the Melinau Gorge by approximately 2.2km.

The geology of this side of the mountain is strikingly different to that of the Clearwater Cave system and it is now accepted that the passages associated with Wonder/Conviction Cave have been formed by water flowing from the Hidden Valley in a northerly direction. Previously it was commonly assumed that the water flowed south, having sunk in or flowed through the Melinau Gorge area. Surprisingly for the highest cave in Mulu, many active streams were encountered, some of which are quite large and responsible for localised flooding, which was experienced at first hand. Although no dye tests were conducted on this trip, it is thought that this water also flows north to the Melinau Gorge, perhaps to resurge in the upper/eastern side. If so, it may then flow downstream in the gorge to subsequently sink once again into the limestones and flow via the Whiterock River to resurge finally from Clearwater Cave. Future dye traces will be able to shed light on this possibility.

There are also subtle differences in the geology and cave morphology; the Wonder Cave extensions differ from the rest of Mulu, especially in the form of the large scale vadose downcutting. This has left behind some spectacular examples with clear scallops in the deep trench walls that indicate the northerly flow.

Demobilisation from the Hidden Valley was done on foot and all expedition equipment was extracted by porters over a period of 5 days, using a transit camp close to Batu Nigel.

2) Clearwater Cave – Mark Brown

Creedence Series

The Creedence Series was entered in 2014 via climbs from the Scum ring area of Clearwater Cave; numerous leads were left unexplored, running in all directions. An entrance at the far northerly extent was reached in a large doline (named High Noon) but surface access was not established that year.

The 2017 team located the doline from the survey coordinates and a fly past in the helicopter en route to the Hidden Valley; they subsequently established a route overland to the High Noon entrance. The route goes steeply uphill for 550m, close to Solo Cave, and then traverses rough ground around dolines, enabling the entrance to be reached in approximately 5 hours, slightly quicker than the alternative route through the cave to the northern limit of exploration. From High Noon, four underground camps were used to explore leads in the top level of the Creedence series, as well as one camp at Scum ring to explore leads in the mid-level, “Bladerunner” area, of the series.

One series of passages continued further east beyond the current extent of any known passages at a lower level in that part of Clearwater, reaching a point 1.5km from the Cloud/Cobra/Bridge Cave System, south of the Hidden Valley. Surveys established the highest point in the Clearwater system at 570m above sea level. Several team members traversed the cave from High Noon Entrance to Clearwater Resurgence, a trip that involves a vertical range of 450m, a cave passage age range of around 1.5million years and a spectacular variety of cave landscapes along the way.

A total of 5.3km of new passage was explored, surveyed and photographed in the Creedence Series, adding considerable information on the layout and geomorphology of the area. Palaeomagnetic samples were also collected from several locations in this, the oldest known part of the Clearwater Cave System.

Cave of the Winds – Eureka Chamber

As part of the connection team project (see below) a new chamber was entered from Clay Hall in Cave of the Winds (which is part of the Clearwater System), named Eureka. This chamber was 200m long with spectacular formations, and is geomorphologically significant because it showed that passages could cross the line of the Cave of the Winds River, heading towards Racer Cave. 1.4km were surveyed in passages associated with this Chamber.

Secret Garden

Passages that had been surveyed in the Secret garden area of Clearwater in 2015 were tied in to the Clearwater survey model during the expedition.

Overall, 6.8km were added to the length of the Clearwater Cave system, taking it to a new overall surveyed length of 222km. This maintains its position as 8^th longest cave in the world, only 470m behind the Lechuguilla System in the USA. Clearwater is the now the third longest cave system in the world to have been formed by river solution (rather than hypogenic or tidal mixing caves) and probably the largest cave in the world by passage volume.

3) Connection project

The objective of connecting Cave of the Winds (part of the Clearwater System), Racer Cave and Lagang’s cave, all in the southern “peninsula” or “toe” area of Gunung Api, was established after new discoveries in 2014 suggested that the caves were very close and could possibly be linked. The connection would add over 12km in length to the Clearwater System, making it a worthwhile objective. Careful survey work and exploration of numerous passages and aid climbs, many of which were tight, muddy and challenging, were carried out.

Eureka chamber was a significant discovery (see Clearwater description earlier), which brought Cave of the Winds and Racer Cave to within 10m of each other. A sump was discovered at the very end of the expedition, where teams on both sides made radio contact and could hear each other hammering on rock, but no lights could be seen through the sump and its passage was very constricted.

Work in Lagang’s and Racer Cave (via the Easter Cave section surveyed in 2014) also brought those two caves very close together but connections remain elusive. It has been proved that passages in all the caves are the same geomorphologically, but interrupted by calcite or sediment blockages or breakdown. The survey will help direct future attempts at a connection.

In the process of the exploration, 1.3km were added to Lagang’s Cave, making it just under 8km total length. 430m were added to Racer Cave, making the total length 6.7km and 1.4km were added to Cave of the Winds, as described in the Clearwater Cave section above.

4) Sarawak chamber climb

3D laser scanning work in 2015 had suggested the existence of high level passages in the roof of Sarawak Chamber. There was also a conundrum that the size of the current passages entering and exiting this massive chamber seemed too small to explain its formation. A team camped in the chamber and carried out a bolt climb to investigate. The initial route entered an area of poor quality rock, requiring a restart on the opposite wall, which was more overhanging and technical. At a height of 80m above the start point a small passage was found, but it dropped back into the main passage, and was not the large feature that had been hoped for.

5) National Geographic

The National Geographic photographer and journalist were assisted by the expedition members and local assistants to gather a range of material for their assignment.

6) Preliminary Science report – Dr Andrew Farrant.

The 2017 Expedition had several scientific objectives. The first was to refine the chronology of the caves by collecting some additional palaeomagnetic samples from the upper levels of Clearwater that had been discovered in 2014. The second was to get a better understanding of the elevation and gradient of the notches in the southern part of Clearwater by surveying them using laser range finding equipment. The elevation of the notches will be compared with palaeoclimate data derived from speleothems in the Mulu area to see if it is possible to correlate notch formation with specific climatic events. The third objective was to combine speleogenetic observations in the caves (scallops, notches, phreatic and vadose passages) with sediment data to better understand the speleogenesis of the Mulu caves over time.

Palaeomagnetic sampling

Palaeomagnetic samples were collected from 9 sites in Clearwater Cave and Conviction Cave, each site consisting of 6 sediment cores 25 mm long and 25 mm diameter. Four were taken from the Creedence Series, the passages at the highest level in Clearwater Cave, and an additional two from Leap in Time near the Secret Garden. Three samples were collected from Conviction Cave. These will be analysed at the Palaeomagnetic laboratory at the University of Liverpool. However, it is clear that the classic fine grained ‘cricket muds’, associated with the notches in the lower part of Clearwater which were extensively sampled in 1991, are absent or poorly developed in the higher-level passages. In the upper levels, the finer grained sediments were interbedded with gravels, and are not likely to be so good for palaeomagnetic analysis. This may hinder the acquisition of a reliable palaeomagnetic signal from the samples.

Palaeomagnetic samples, Creedence, Clearwater Cave.

Notch Elevations.

The initial assumption was that the notches in the Mulu caves are formed by the throughput of copious amounts of gravel during wetter climatic periods over the last 2.5 million years. This causes the stream to erode laterally rather than incise into the floor of the passage, forming a notch. The advent of better surveying techniques, including the use of laser range-finding devices linked directly to cave surveying software means that accurate elevations and gradients for the notches can be obtained with far greater precision and tied back to fixed surface GPS points. Assuming a constant rate of uplift and valley incision, the age of each notch can be estimated from the palaeomagnetic timescale, and then correlated with global climatic events and climatic data obtained from speleothems in Mulu by Kim Cobb and others.

A preliminary correlation with the Mulu speleothem climate record and notch elevation (=age) suggests there is no clear relationship between notch aggradation and climate. However, fieldwork during this expedition indicates that the notches are far more complex than initially assumed, with some notches having multiple sub-notches, and significant gradients over the length of the Clearwater system. In addition, notches are associated with fan aggradation from both the Melinau Gorge and the Melinau Paku rivers, and so are influenced by different catchment dynamics and responses to climate forcing. There are also likely to be significant lead times from the onset of wetter climatic periods and the aggradation of the cave rivers and notch formation, which is dependent on the distance from the sediment source. This is possibly on the order of several thousand years for the downstream parts of the Clearwater system. Furthermore, aggradation and notch formation in the cave passages is dependent on water from either the Melinau Gorge or the Melinau Paku River being routed through the cave system and bringing in gravels. This is not the case with the present drainage from the Melinau Gorge, where the water comes in via boulder chokes which filter out much of the coarse bed-load. Lastly, whilst the modern DistoX surveys are more accurate than the 1978 cave surveys (from which notch elevations were estimated from cave elevation drawings), there is still some data processing to do with the survey data to get the final elevation for some of the notches. Further work and data processing is required to tease out any correlation between palaeoclimate and notch generation.

Speleogenesis

During the course of the April 2017 expedition, observations of cave geomorphology and geology were made in parts of Lagang’s Cave, Cave of the Winds, Racer Cave and Clearwater. In addition, the analysis of digital cave survey data viewed in Survex is yielding new insights into the influence of the geological structure on cave formation. Much of the cave passages in Mulu are influenced by geological structure, most notably the strike of certain favourable bedding planes, and two sets of joints, one trending approximately N-S, the other E-W. In the northern part of Gunung Api, the geological structure appears to be relatively simple, with the limestone dipping steeply to the NW at around 60-70°. Most passages in Whiterock are orientated along the strike of the limestone, typically trending at 210-220°. To the south, the strike of the limestone gradually shifts to a more southerly orientation. This is clearly visible in Armistice and Creedence where the passages along strike trend at 195-200°. In the lower levels of Clearwater, the strike is more to the SSE, before swinging back around to a NE-SW trend in the southern end of Gunung Api; here Lagang’s cave trends at 220°. In this part of the cave, the dip is noticeably gentler, at around 25-30°.

Joint patterns are also clearly evident from the cave surveys. The E-W trending joint set is clearly visible in the Armistice and Creedence areas, and in the Secret Garden-Hyperspace-Battleship area. These joints are often used to transfer water laterally from the older beds lower down in the dipping limestone sequence up through the limestone to the younger beds in which the Clearwater resurgence is located. An alternative way for the water to transfer stratigraphically up through the limestone sequence is to descend down-dip and then ascend up a phreatic joint-aligned riser. This is what happened at Deep Thought and Ronnie’s Delight pitches near the Scum ring camp, where water transfers up joints into higher level limestone beds. The same thing happens at Coral Aven in Lagang’s Cave, albeit it at a much smaller scale. In the southern part of Clearwater and the Lagang’s-Racer Cave area, steeply inclined joint sets are often the dominant influence on passage orientation, for example in Fast Lane, Lagang’s Cave.

The exploration of the Hidden Valley cave systems also hints at a structural influence on cave development. The new extensions in Conviction Cave suggest cave development is orientated along the axis of a shallow plunging syncline trending at 220°. Further discussions with the Hidden Valley team and a detailed analysis of the cave survey data are needed.

Sediments and speleothems

During this expedition, several new volcanic ash localities were found, both in Lagang’s Cave and in Creedence, in Clearwater Cave. A potential objective of any future expedition would be to find any speleothem material above or below the ash deposits to better constrain the age of this super-eruption. In addition, some qualitative assessment of the gravels was made in Creedence and Hidden Valley which suggests that the inputs from Hidden valley are dominated by siltstone, unlike the Melinau Gorge which is sandstone dominated. In the Hidden valley, unusual yellow encrustations on cave popcorn and moon-milk deposits were found in Conviction cave, which were collected for analysis. These may be bacterially mediated mineralisation on evaporitic calcite speleothems.

Allophane deposits (weathered volcanic ash) in the Creedence Series.

For the sample list please see the Appendix of this document.

Conclusions

Work in all the components of the expedition has greatly added to the knowledge of the caves, geology and geomorphology of the Gunung Api area. A total of 21km of new cave passage has been surveyed, most of it using modern digital techniques that provide a high degree of accuracy. A large amount of resurvey work has also been carried out to refine the 3D model of the cave systems under Gunung Api.

The different components also had a positive feedback effect; for example, the exploration teams helped collect data for the science and the science work informed the exploration, typified by the Eureka Chamber discovery.

As ever, the expedition came away with a good number of leads and new questions to be answered by future expeditions.

The expedition was also conducted safely, with good emergency planning, and no incidents or accidents were reportable.

A detailed description of all aspects and findings from the expedition will be published as part of the Anglo/Malaysian, Mulu Caves Project 2017 report.

Acknowledgements

From Sarawak:

The Chief Minister of Sarawak
The Sarawak State Secretary
The Director of Forests, Sarawak
Protected Areas & Biodiversity Conservation Unit, Sarawak Forestry Corporation
Gunung Mulu National Park Management & Staff
Local organisers and assistants
Oswald Braken Tisen
Rambli Ahmad
Veno Enar
Richard Hi (Tropical Adventure)

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The expedition is very grateful for the support of the following sponsors and organisations.

National Geographic
Five Ten Ltd.
Spanset Ltd
Ghar Parau Foundation
Mark Wright Training Ltd
Tex:Energy
Wolfride Clothing

* A full list of acknowledgements will be published in the final report

For further information log on website :
http://www.mulucaves.org/wordpress/expeditions/mulu-caves-2017

Cloud Cave

Discovered: 1996

Length: 2,209.90m

Vertical Range: 220.13m

Connections: Bridge Cave, Cobra Cave

Part of: The Cobra/Cloud/Bridge Caves System

The entrance to Cloud Cave lies near the base of the fourth depression and is so large that clouds form in the entrance. The main passage is huge, being 80m high and 45m wide heading northwards towards the Hidden Valley to end in a total choke after a kilometre. Interestingly this choke is 100m below the level of the present day alluvial sinks in Hidden Valley, leading us to wonder if this was the original conduit of the Hidden Valley water or does it predate the valley and pass under it towards the summit of Gunung Api?

At the base of the enormous boulder ramp is a tall stream passage and an obscure duck under a hole in the wall provides a connection through to Cobra Cave which was explored from a camp in the Melinau Paku valley in 1984. The early explorers turned back at the end of Cobra, thinking that the passages were closing down, a few more metres and they would have found their way into the Cloud System twelve years earlier!

Bridge Cave is connected to Cloud Cave in two places, both down deep pitches. One of them, a huge 30m diameter, 95m deep shaft, The Abyss, has never been descended despite two attempts, although markers dropped down it were found at the base of a huge aven in Cloud Cave, proving the connection.

Cloud Cave 1998

For further information log on website :
http://www.mulucaves.org/wordpress/the-caves-2/caves-of-gunung-api/cloud-cave

The Cobra/Cloud/Bridge Caves System

When explorers discovered Cobra Cave in 1984, little did they know that they had stumbled on the lower end of Mulu’s deepest cave sytem. It would be a further fourteen years until this became a reality.

Total Length: 20,632.27m
Vertical Range: 489.40m
Component Caves:

Cobra Cave – discovered 1984
Cloud Cave – connected 1996
Bridge Cave – connected 1998
Train Cave – connected 2012

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The most spectacular caves on earth

In Borneo, deep in Sarawak’s Gunung Mulu National Park, lie the most spectacular caves on earth. Over millennia the flow of water draining from the slopes of G.Mulu towards the sea has cut deep gorges through the Park’s limestone mountains and, within the rock itself, a complex network of vast caves has been formed.

Since 1978 these caves have been the focus for a succession of expeditions and this website holds a record of the discoveries made during that period.

As we move into the 21st Century, humanity appears to have explored to the limits of our environment. Using technology we can photograph the surface of distant planets, probe the immensity of space, scan the beds of the deepest oceans, image the inside of living bodies and picture the surface of structures to microscopic detail. In such a world, it might be imagined that there is no true exploration left to be done. But this would be untrue.

Under the surface of our planet lies a parallel world, a world of great beauty and mystery formed over thousands of years by the most elemental of forces, the passage of water through rock. This world, the domain of caves, remains largely unexplored. In northern Sarawak, the Mulu Caves Project is making progress on this journey of discovery

For further information log on website :
http://www.mulucaves.org/wordpress/

Exploration History

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

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 4^th 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.

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 next expedition will be in Sept/Oct 2015.

For further information log on website :
http://www.mulucaves.org/wordpress/history-of-exploration

Mulu Caves ‘96

With the ‘93 recce providing sufficient leads to justify a full expedition the team headed off into the unknown and inhospitable terrain of the Hidden Valley dolines.

During October 1996 members of the Sarawak Forestry Department together with 8 British cave explorers visited the Hidden Valley area of the Gunung Mulu National Park in northern Sarawak. Seven new caves were discovered and a total of 10.5km of previously undiscovered cave passages were explored and surveyed in the deep dolines beyond the Hidden Valley gorge. The Expedition entered totally unexplored areas of the Park which, due to the inhospitable nature of the terrain, had never before been visited by man.

A camp was established near the ‘93 camp. Although this was of grander proportions it soon became a rather squalid and damp home. A cook house was erected adjacent to the stream but flood waters washed through this on a regular basis. Owing to the heavy rains experienced during the expedition the river beds which had proved such useful roads on the recce had become fast flowing rivers, best avoided.

At the lower end of the valley a large low-level entrance was discovered named Damocles Cave. This had been seen by Park guides during the ‘93 recce but not recorded. A large entrance led into a major passage which quickly choked. The only onwards route was downwards onto a series of pitches which resembled a classic Yorkshire pothole. A final 35m pitch led down into a horizontal continuation which headed wide open in a southerly direction. However, owing to the fact that this cave formed the main sink for the western end of the valley and that heavy rain was experienced on a daily basis it was considered prudent to leave it unexplored beyond this point.

Beyond Damocles Cave the ground rises up from the flood plain of the valley floor onto limestone terrain. This ground makes very difficult going with loose boulders, pinnacle karst, deep pits, dense forest and a series of deep dolines.

This inhospitable area was the key to the major discoveries of the expedition.

Above the first doline No Name Cave was found on the southen slopes. In the second doline Arch Cave had been noted as an open lead in ‘93. This was explored along a stremway in both directions and eventually connected to Yellow Viper’s Pit which the surface track passed and which dropped into the upstream section.

In the third and deepest doline Perseverance Cave was discovered in the west wall and on the opposite side of the same doline Bridge Cave was discovered within a collapse feature which contains a magnificent natural rock arch.

In the fourth Doline Cloud Cave was discovered, this contained a main passage of Deer Cave proportions.

Further minor entrances were seen in the surrounding area incuding a large calcited entrance high above the fourth doine which had been seen from the air and was named Helicopter Cave. Unfortunately attempts to gain acces to this were thwarted.

Towards the end of the expedition exploration down a deep bouldery ramp in Cloud Cave led to a connection with Cobra Cave in the Melinau Paku valley. This link establised the Cobra/Cloud System as the deepest cave in the Park.

For further information log on website :
http://www.mulucaves.org/wordpress/expeditions/mulu-caves-96

Hidden Valley ‘93

Hidden Valley, situated on the eastern flank of Api, presented unique difficulties for exploration. Significant discoveries had been made during the 1978 expedition but there remained great potential for more secrets to be revealed among the pinnacle karst of the Hidden Valley dolines. The remoteness of the area and inhospitable terrain made these the most challenging of all Mulu expeditions.

During January 1993 a six man team supported by Park guides and penan porters carried out a lightweight reconnaissance expedition into the Hidden Valley on the eastern side of Gunung Api. This was the first expedition to explore this area of the Park since the Royal Geographical Society expedition of 1977/8. The expedition aimed to cover as much ground as possible in the limited time available to gauge the potential for a future caving expedition to this area. A small and rather squalid camp was established in the centre of the Hidden Valley gorge between the entrances of Prediction Cave and Wonder Cave and just above the flood plain.

Prediction Cave was re-located and six other previously undocumented entrances were recorded. The weather conditons were dry and any water running into the gorge disappeared into sinks as soon as it hit the limestone. This left a dry river bed downstream of the camp which provided a useful highway to explore the the bottom end of the valley.

A search around the walls of the gorge revealed some entrances which would require equipment to gain access, these were noted for future reference. At the western end of the gorge the ground rises up from an alluvial plain and onto a rugged and inhospitable karst landscape which is covered in dense vegitation. Exploration continued into this area which passes through a series of deep dolines. The first doline revealed nothing but in the second doline a cave was found and named Lawai’s Cave. This was later renamed Arch Cave. No exploration was carried out but this was noted as a significant find. Other small entrances were found in this area and it was thought likely that potential existed here for significant discoveries.

Exploration stopped at the southern side of the second doline but it was known from aerial photography that the valley turns south from this point to cross more deep dolines before emerging high above Good Luck Cave in the Paku Valley.

Although no underground exploration was carried out during the three days which the team were in the valley, sufficient entrances had been found to justify a full scale expedition to the area.

For further information log on website :
http://www.mulucaves.org/wordpress/expeditions/hidden-valley-93