Central River Meanders - Revisited
by Mark Staraj
Seven years have passed since I wrote the original article "Central River Meanders" [Staraj 1989b] - plenty of time for new discoveries and new conjectures.
Knowledge of Central River has increased markedly principally due to droughts in the years 1991, 94 & 97. Sketch maps now exist for a small extension downstream of Central Lake and for moderate extensions up and downstream in Risky Business (formerly Second Crossing). High grade survey now links First Crossing through to the Railway Tunnel Extension and almost completely through to The Overflow. A half complete survey has been made of Streamway to Heaven, the best find of intervening years and now the most remote point of Mammoth Cave.
To see how the last 7 years has filled out the emerging picture of Central River please read on. In order to offer a sense of perspective I have decided to revise the original article mostly by annotation rather than rewrite it. Where the original text has been altered to improve accuracy I have attempted to clarify with either insert or endnote.
Central River is the current central pillar of Mammoth Cave hydrology. Although but a tributary of the Jenolan Underground River (JUR), it or its feeders are responsible for forming the bulk of Mammoth's 7km (#1) of passage by length. As can be seen from the map, it underpins most of Mammoth like a backbone.
Central River, like most cave features, has its own intriguing riddles and enigmas. In spite of its vicinity to the JUR it has managed to develop considerable length and an extensive inflow network. This seems to be primarily tied to dominant geological factors. Its ultimate source and destination are both unknown with any certainty: somewhere upstream is its first tributary, and somewhere downstream it joins the JUR.
In character Central River has a small base flow of 1.5 millicumecs when compared with the JUR (140 millicumecs at its appearance in Mammoth) [Shannon 1976]. It responds readily to heavy rain and has been known to dry up completely in severe drought. For the most part Central River flows through low and inaccessible passage.
This article will review the known sections of Central River and make some conjectures about the river and further potential from these sections. It is an overview of facts and observations about the River and contains recent material and perhaps other unknown material for some. Hopefully it will stimulate further thoughts and perhaps a few projects.
The source of Central River is conjectured by H. Shannon [Shannon 1976] to be Hennings Creek and associated alluvial storage. This is based upon the following observations: rises in Central River coinciding with advances of Hennings Creek or of the Jenolan River to the Serpentine area, the sinking point of Hennings Creek (see map) and the tracing of flourescein from a surface tributary opposite Serpentine Cave in August 1972 to Central River [Shannon 1973a].
Finding cave extending to this source would double the distance to Mammoth's most northerly point from its entrance! A very long and arduous trip it would be too without a second entrance. To find such a beast would require the digging of potential caves near Hennings or in between, or the pushing of passage from the Great North Cavern area or alternatively upstream from Risky Business (formerly Second Crossing).
Other known tributaries of Central River are the stream from Waterfall Passage, flood flow from the Infinite Crawl, possibly the stream appearing in Twiddly-Om-Pom (that is if it is confirmed not to be the major portion of Central River) and that appearing in flood in Great North Cavern.
One additional tributary has been found since 1989 - that of Streamway to Heaven. Another possibility may be the similar streamway found in the Eastern Extensions which is presumed to run into the Ice Pick Lake area.
A bluff, previously unnamed, but now dubbed Millennium Bluff is situated further north again than Hennings Creek. Prospects for finding a significant cave there would seem to be nil. However the prominent stream sink in the gully to the north may indicate that Central River drainage extends some 300m further north again than Hennings Creek.
The search for the fabled back door is most likely to succeed in the vicinity of Kia Ora Hill Bluffs where a couple of promising yet difficult blowing leads have been receiving periodic attention from SUSS over the past decade.
Twiddly-Om-Pom is a fairly large cavern situated below and to the east of Great North Cavern. Reaching it is the hardest trip in Mammoth Cave. At its most northerly point, beyond Mud-in-your-eye Squeeze, is a short portion (6m) of stream. It is reported as unpushable in either direction. Almost any rise in the stream causes it to overflow down through the squeeze and sump Twiddly-Om-Pom at its southern end, and is joined by other streams arising out of other parts of the cavern.
The stream itself was dye traced in Jan 1973 to Central River, however in Shannon's opinion it represents less than half the flow into Central Lake [Shannon 1973b]. Thus it may represent a major tributary of Central River only (or even an anabranch).
Apart from finding passage to bypass the obstructions in the stream passage, the best prospect is to follow the course of the overflow, as it is certain to rejoin Central River further south. The connection may provide the route required to follow Central River further north providing the Twiddly-Om-Pom stream does not represent the main portion of Central River.
In 1995 the overflow was indeed followed and the sump had dried up due to the drought. On the other side was revealed Central River and a steeply ascending boulderpile containing an inlet. This inlet was named Streamway to Heaven and the passage was followed up vertically to a height of 35-40m. Central River emerges from an impenetrable crack and after a few metres runs into a sump - Silly Bugger Sump. During further drought in 1997 this sump retreated revealing some 30m of passage trending towards Damocles Lake in Risky Business. [Jackson 1995, Fairlie-Cunninghame 1995].
This part of Central River is in all probability the reappearance of the stream last seen near Mud-in-your-eye squeeze so if it is a tributary of Central River then it now seems unlikely that its junction with Central River will be accessible from the vicinity of Twiddly-Om-Pom. However I am inclined to think that it is Central River proper.
On the other hand two digs offer possibilities of passing the obstruction upstream in Twiddly-Om-Pom. One, as I recall, is described by Pavey as situated some 10m higher than Mud-in-your-eye Squeeze in a muddy tube [however I was unable to relocate the reference]. More likely to succeed might be the dig dubbed "The Way to Rabbit's House" described most recently by Jackson [1995]. However both of these should be considered long term digs.
This is quite a large cavern containing a normally dry stream passage: Cycloidal Passage. During flood, water has been observed pouring out of avens in the roof of the Cavern and vanishing in the floor near Cycloidal Passage. Successfully following this may also lead to an upstream section of Central River.
The stream that flows down Cycloidal Passage has been shown to come out in Twiddly-Om-Pom [Jackson 1995], so only a convenient route to Twiddly-Om-Pom will be gained here.
A more determined investigation of the north side may yield results but I feel that it will prove to be substantially blocked by sediment and rockfall. It seems to me that in the past that it was the inlets from the roof that kept North Tunnel open.
The avens have been climbed on a number of occasions but become impenetrable.
Risky Business (#2) occurs near The Junction: the heart of a complex nexus of streams. It contains about 35m of Central River. Downstream it can be followed through a tight series of joints and upstream over pools and small (1'-2') waterfalls, with both becoming impassable after 50' or so. During floods Central River overflows into The Junction from where it fills the Dry Siphon and drains to The Overflow (see map).
The best prospect is apparent from the map, that is to push upstream from Risky Business towards its source. While the going might be hard along the River itself there is always the chance of breaking through into extensive, drier, upper passage, which so far has been found to reach the furthest point of Central River (Twiddly-Om-Pom)
This section was explored during drought in 1991 [Norton 1991, Staraj 1991] when the upstream sump had reduced to a duck under. Beyond 2 tight squeezes (one in unstable rockpile - the Coup d'État) the stream led to a sump - Damocles Lake. Not yet surveyed, the entire upstream section is estimated to be about 40m long. The terminus sump proved to be quite interesting when droughts in 1994 & 1997 caused it to disappear entirely revealing a completely mud choked passage. However a blowing rift between Coup D'État and Damocles Lake, obstructed by a large rock, would appear to offer good prospects of continuation at a higher level. The prediction of hard going leading to upper passages looks likely to be fulfilled.
Downstream, the prospects were not held to be worth the effort. Nonetheless the 1997 drought enabled David Jackson a chance at cracking the fearsome squeeze labeled The Liquidator without risking being drowned in the tight and inclined rift. The result was some 15-20m overall of extra passage. After dropping 6m in height the stream left the rift to flow in a tube that diminished in height and petered out into a sump. Total distance reached downstream is approximately 25m.
Can't Get Lost is the most northerly known continuation of the same large passage as Railway Tunnel, separated from it by a very big rockpile. During the successful climbing attempt to reach Brittle Bazaar located above Can't Get Lost [King 1975] one of the climbers dropped something at the base of the pitch. In a search for it Randall King found a hole amongst rocks at the bottom of the pitch. Through the unnegotiable hole he could see Central River some 80' to 90' below.
This section of river lies exactly where it would be expected. It has very limited prospects as a short distance in either direction the river appears in Risky Business and The Overflow.
This lead has not been reconsidered.
During conditions of high flood Infinite Crawl carries water to Central River via The Overflow. In April 1972 flourescein placed in Wiburd's Lake Cave was detected in Lower River (JUR appearance in Mammoth Cave) and was concluded by Shannon to have also appeared in Infinite Crawl and hence Central River [Shannon 1973a]. (This is based on the likely and uncontradicted assumption that water flows in the Infinite Crawl only during flood and did not flow between August 1972 and January 1973). Since tracing done directly in Central River has never indicated an upstream link between Central River and Lower River then Shannon came to the important conclusion that Infinite Crawl is directly linked to The Woolly Rhinoceros (JUR upstream of Lower River)!
Although it sounds promising, exceedingly hard work is required to realise the link. The passage has been pushed some 300m and is increasingly low and tight. An occasional mild breeze and the presence of sand support its promise but Dick Williamson, who is said to have penetrated the furthest found it so tight that he had eventually to be hauled back by a rope!
Easier upper passage as an alternative is still possible but most (if not all) of the avens nearby have been climbed and proved blind.
In February 1972 another flourescein test was performed where it was placed in the stream sink of the Jenolan River opposite the upper entrance (#3) of Serpentine Cave [Shannon 1972]. The Jenolan River was sinking only as far as the scour hole opposite Little Canyon Cave (#4), just south of Serpentine. Inside Serpentine no stream was flowing. It was later detected in Central River and is hypothesised to have reached there via the Infinite Crawl. Infinite Crawl itself was found to be flowing but not directly into The Overflow.
There have been at least 2 other visits to the "end" of Infinite Crawl and both concluded that the dig would be a very difficult and long term project. Bruce Welch believes it may lead to vast innumerables - quite possibly but is it realisable?
No verification has yet been done on Shannon's hypothesis about the JUR/Infinite Crawl link. So the only result we have is the connection between Jenolan River (McKeowns Creek) outside Serpentine Cave and Infinite Crawl. Another option not discussed above is that the Infinite Crawl is fed by the Serpentine Intermittent Stream (the stream that flows within the cave during floods). This possibility is raised by Scott [1993]. All 3 options are not necessarily mutually exclusive.
Usually a trickle and at most a little stream exits this passage from The Breezehole, flows to form a pool in the Dry Siphon and thence joins the nearby Overflow. The breeze in the lower part of the passage is persistent and of moderate strength. It has fueled expectations of an upper entrance in the vicinity. The stream is followed upwards to a high cleft in crumbly rock. This is the limestone-shale interface. The stream is thought to derive from a surface tributary. The top of the cleft is some 30-40m above The Breezehole. While the prospects are good of attaining the fabled upper entrance of Mammoth, in reality they are defeated by the unsafe nature of the shaley rock.
Due to the stream and the breeze this passage is something of a beacon to explorers. SSS attempted the cleft with scaling poles. The results were spectacular if unrewarding. A large chock stone slipped and wedged some metres above the party [Mason 1972]. Unless it is behind this chock stone it is hard to see where the continuation lies. The breeze cannot be traced at this point and the stream falls almost vertically at one end of the cleft from a crack in a small room below the chock stone. So the key to it all is being able to pass the chock stone to determine further where the stream is coming from.
Most intriguing is the stream - it never seems to dry up! Just what source this points to won't be clear until a good correlation is available between Waterfall Passage and the overlying topography (no survey currently exists for Waterfall Passage - one was made but was then lost).
The Overflow carries floodwater from Infinite Crawl and possibly even from Risky Business via The Junction in very high flood. The chamber at the end of The Overflow contains yet another section of Central River (about 10m length). Upstream is impassable and downstream the River sumps to a depth of 10'. Near here another stream enters the sump. In January 1973 dye placed in the stream in Twiddly-Om-Pom was observed in both of the streams in The Overflow, proving one to be the anabranch of the other [Shannon 1973b].
Water also enters The Overflow directly from The Junction.
The Overflow was twice visited during drought in 1994 and 1997. Both times the sump had dropped about 3m but still contained a lot of water. Surveying done upstream from First Crossing [Staraj 1995] seemed to reach the other side of The Overflow sump and would indicate that this sump is the lowest point in Central River between First Crossing and Twiddly-Om-Pom. Whether the sump contained only residual water or is still being fed by the flow from Waterfall Passage is hard to say. Nonetheless it is claimed by SSS that in early 1978 The Overflow sump dried up completely allowing two members to traverse along Central River from Railway Tunnel Extension right through to The Junction [Staraj 1995 Appendix]. I have not yet sighted a report for this rare event - other interesting observations may be contained therein as well e.g. did Waterfall Passage dry up?
Upstream in The Overflow sump the streamway can only be followed a handful of metres until it becomes too narrow. This route appears too juvenile to negotiate. The former route for Central River may have emerged from under the rockpile found in the chamber some 10m back from the sump room. This may hold the key to tracing the streamway back towards Risky Business.
This is a rather spacious series of passages and chambers containing about 25m of Central River [Bonwick 1979]. It is reached by a couple of pitches from the northernmost part of Railway Tunnel. Both ends of the river end in sumps.
Not far from the downstream sump lies the upstream sump of First Crossing and little would be gained here. However some 50-70m still separates the upstream sump and the sump in The Overflow and so substantial passage can yet be found. However the biggest prospects may rest with more Railway Tunnel as a portion of the Extension reaches rockpile at the same height as the rockpile at the end of Railway Tunnel and approximately half way between it and the start of the Can't Get Lost section.
A trip in 1978 by SSS, discussed in Section 9 The Overflow, managed to penetrate north from the Railway Tunnel Extension right through to The Overflow. However it was not until a further drought in 1994 was a survey able to be made of this section although the Overflow sump prevented completing it right through. Still the best potential lies at Railway Tunnel level but this section remains infrequently visited due to the need for ladders.
Central River issues from a rockpile and flows from here to Central Lake. Depending upon water level it is possible to push some distance down the passage and during drought Central Lake can be reached. Upstream the river can be pushed under the rockpile, past where an aven connects to the Ninety Foot shaft in the Railway Tunnel above, through more very unstable rockpile to 7m of stream passage and finally a 3m deep sump [Cox 1977]. This is close to the downstream sump of the Railway Tunnel Extension and so has no prospect.
In 1990 the unstable rockpile (which had collapsed) was successfully bypassed with a much safer route. This enabled ready access for a survey in 1994 when Central River had dried up, so now a survey exists from First Crossing almost right through to the Overflow. First Crossing's value lies now in easy access to the Railway Tunnel Extension during a drought.
Until very recently this would have been considered the southernmost known appearance of Central River. The lake is very variable in height and responds rapidly to increases in Central River. At its lowest it is but a sump pool (#5). Normally it is a lake seen to be a few metres below holes in the floor of the passage connecting the start of Snakes Gut passage to First Crossing. In high flood it emerges from the holes and floods a portion of this passage with the lake extending as far back as First Crossing. In extreme floods it is now known to completely submerge the passage producing a spectacular waterfall into the Snakes Gut passage [Staraj 1988]. At such a time First Crossing would be submerged to a depth of 5m or more [check reference for height].
Central Lake disappears completely in the worst droughts. However since this route is relatively new for Central River it seems unlikely that any drought will provide further penetration past the next sump.
Referring to the waterfall mentioned in the section above, all this water disappears along the Snakes Gut passage in the direction of Ice Pick Lake (IPL). However prior to reaching IPL it must flow into the "hole to water". On a trip in 1987 the water level in this hole and IPL were at normal levels (i.e. those shown on the map) [Staraj 1989a]. The conclusion is that the hole and IPL are hydrologically connected and part of the same body of water.
A dive in IPL in 1980 by Ian Lewis of CDAA [Lewis 1980] found a series of small passages linking larger chambers for a distance of 70m and 17m depth, but had to turn around due to using up his air - the passage just kept going. Thus the IPL system both holds and can receive a lot of water (after an extreme flood in 1975 [Welch 1975] and after the waterfall had operated (not realised at the time), the level of the IPL system had risen to just 4m below the top of the waterfall). In time the levels return to normal and is not known to drop much below this even in drought.(#6)
This raises the following question: Where does this excess water from the IPL system drain to?
From inspecting the map it seems most likely that it in fact drains back into Central River downstream of Central Lake. Supporting this is the observation above of increased levels without a flood. It seems that the level of the IPL system is not so much related to the level but to changes in level of Central Lake. This implies that the outflow of the IPL system is connected with another and perhaps smaller sump (in terms of outflow or capacity) of Central River downstream of Central Lake. IPL is then a permanent lake with an open water connection to this hypothetical sump. In times of flood this sump banks up, to overflow into and raise IPL, and maybe in part to cause a corresponding rise in Central Lake.
As for the origin of the flooded chambers making up the IPL system one explanation could be as follows. These chambers are in the phreas zone. That is they are flooded because they lie below the water table. In the absence of a geological anomaly the water table would be defined as the approximate height above sea level of the JUR (i.e. Lower River). I have not seen or heard mention of the relative levels of IPL and Lower River but experience indicates they would be very close. Central River would then represent a separate JUR.
On a separate note I should mention that on the trip in 1987 [Staraj 1987] in the rising passage just as you pass the "hole to water", I experienced the strongest breeze I have ever felt anywhere in Mammoth, literally blowing the hair back from my head! No where have I heard a mention of airflow here. It is worth noting and thinking about. Possibly cooler air descending from the high avens in Naked Lady Chamber nearby.(#7)
A dive was conducted by SUSS in 1996 in IPL but failed to find anything like that reported by Ian Lewis. A constricted passage was found at 6m depth but was not penetrable. It is most unlikely that another passage exists so it appears that considerable silting has occurred since 1980. Ron Allum also reports on another example of this in Slug Lake, Mammoth Cave [Allum 1990].
Recent survey work by SSS has fixed the height of Ice Pick Lake above the level of Lower River (JUR).
The airflow described in Snakes Gut has now been traced to a major new series of passages - the Eastern Extensions, which now contains the highest point in Mammoth Cave some 30m above the highest entrance. At -178m Mammoth Cave is now the deepest cave on the Australian mainland, surpassing Eagles Nest at Yarrangobilly at -175m. The Eastern Extensions connect into the rest of Mammoth between IPL and Naked Lady Chamber.
These conjectures lead to the next topic…
Where does Central River join the JUR?
We know from the results of a number of dye traces and a comparison of water chemistry [Handel & James 1977] that Central River does join the JUR and does so south of Lower River. Knowledge of the Imperial Divers' Extension and Spider Cave infers it joins the JUR upstream from Spider Cave. The only known tributary is not a candidate as it is normally static. The JUR is not seen between Spider Cave and Lower River (#8), representing a distance of some 500m. Therefore the downstream section of Central River has excellent potential for extensive cave.
How much of this potential could be realised? Note that the overall trend of passage and Central River in Mammoth is NW-SE along the strike. IPL occurs at the easternmost point in Mammoth Cave and must lie near the shale contact seen to the east in Waterfall Passage. It is then a good chance that Central River reaches the contact and with a dip in the limestone increasing from 80o (see map) it can be expected to remain there for quite some distance.
Recent diving in Slug Lake has revealed large and extensive underwater passages lying to the east, and therefore down strike of IPL. The possibility exists then that Central River connects to the JUR via this large network of passages shown to extend within South Mammoth Bluff.
The rest of the original article dealt primarily with the source of the Serpentine Intermittent Stream and really forms a separate discussion. Interested readers are referred to Scott [1993] where this topic has been updated in detail.
References
Allum, R. 1990: SUSS Bull. 30(1):16-18. Dive Slug Lake, Mammoth Cave, Jenolan.
Bonwick, M. 1979: J. Syd. Speleol. Soc. 23(10):237-239. The Railway Tunnel Extension, Mammoth Cave, Jenolan, N.S.W.
Cox, G. 1977: SUSS Bull. 17(4):101. Trip Report.
Dunkley, J. & Wingley P. 1971 & 1978: The Exploration and Speleogeography of Mammoth Cave, Jenolan. 2nd Edition. Published by SUSS and SRC.
Handel M. & James J. 1977: Helictite 15[1]:29-38. A Chemical Investigation of some Ground Waters of the Northern Limestone at Jenolan Caves.
Jackson, D. 1995: SUSS Bull. 35(4):4-8. The Streamway to Heaven.
King, R. 1975: SUSS Bull. 14[10]:119-123. Mapping of Brittle Bazaar Chamber and a search for a new surface connection to this extension of Mammoth Cave.
Lewis, I. 1980: reprinted in SUSS Bull. 20(7):85-87. Cave Diving at Jenolan.
Mason, S. 1972: J. Syd. Spel. Soc. 16(1):16-17. Scaling poles in the waterfall passage.
Norton, C. 1991: SUSS Bull. 32(1):39-43. Some Mammoth Extensions.
Scott, M. 1992
Shannon, H. 1972: Down Under 11(1):17-25. Flourescein testing, Serpentine area - and many other things.
Shannon, H. 1973a: Down Under 12(1):5-6. Unscrambling a botched job on Flourescein tracing.
Shannon, H. 1973b: Down Under 12(1):17-19. A.S.F. Field Trips - Jenolan.
Shannon, H. 1976: The Caves of Jenolan 2: The Northern Limestone. Notes on Geology, Geomorphology and Hydrology.
Staraj, M. 1987: SUSS Bull. 27(3):8. Mammoth Cave - tidbits.
Staraj, M. 1989b: SUSS Bull. 29(2):??. Jenolan: where it never rains but it floods!
Staraj, M. 1991: SUSS Bull. 32(1):35-38. Coup D'État.
Staraj, M. 1995: SUSS Bull. 35(3):23-42. The X(mas)-Files 1994.
Staraj, M. 1998: SUSS Bull. ??(?):?? 1997: The Week at That Private Playground
Staraj, M.1988: SUSS Bull. 28(2):12-18. Gurgles from Mammoth Cave.
Staraj, M. 1989a: SUSS Bull. 29(2):??. Aromatic Jenolan.
Staraj, M. 1989b: SUSS Bull. 29(2):9-20. Central River Meanders.
Welch, B. 1975: SUSS Bull. 15(8):167-170. Some Observations on the Jenolan Flood, 21 June 1975
Welch, B. ed. 1976: The Caves of Jenolan 2: The Northern Limestone. Published by SUSS and SRC.
Map of Mammoth Cave
From Dunkley, J. & Wingley P. 1971 & 1978:
The Exploration and Speleogeography of Mammoth Cave, Jenolan. 2nd Edition.
Published by SUSS and SRC.
#1 Previously given as 4km. Revision is based on current knowledge of the cave and the results of other Jenolan resurveys.
#2 This section was renamed from Second Crossing (which had been used unofficially) to Risky Business following exploration in 1991 [Staraj 1991]. To date this has proved to be a characteristic of all exploration in this area. Another part of the reason was semantics - no crossing of the river occurs here at all, unlike First Crossing which is also an unofficial but useful label.
#3 The Upper Entrance to Serpentine Cave is tagged J125.
#4 Now known as Little Canyon Entrance of Serpentine Cave, tagged J61.
#5 It can actually dry up completely revealing about 10m more of passage and a further sump pool.
#6 In severe droughts it disappears considerably as much of it is shallow. Just one deep pool is left at the southern end.
#7 Indeed substantial cave was found between IPL and Naked Lady Chamber - called the Eastern Extensions - and is currently being explored by SSS. It climbs 98m making it the highest point in the cave - 30m above the top entrance J15.
#8 The JUR has since been found flowing at depths below Slug Lake - about
80m further south than Lower River.