inscribed on
World Heritage List

The Blue Mountains are part of the Great Dividing Range. Just west of Sydney they are also part of the Sydney Basin with which they share their geology. The Cox River marks their boundary in the west and the Lapstone Monocline in the east.

The mountains stretch from Lake Burragorang in the south right north to the Wolgan and Colo rivers. In the heart of this area lies the Blue Mountains National Park.

Together with the Wollemi and Yengo National Parks in the north, and the Kanangra-Boyd and Nattai National Parks in the south, the area became the Greater Blue Mountains and received World Heritage listing in November 2000 for its "wide and balanced eucalypt habitats of wet and dry sclerophyll, mallee heathlands, as well as localised swamps, wetlands and grasslands".
90 eucalypt taxa (13% of the global total) occur in the Greater Blue Mountains, 12 of which are considered endemic to the Sydney Sandstone region (1). Over one million hectares in size (10 000 km² - 3860 miles²) it became the largest wilderness area in New South Wales. It rates among the best bushwalking country in Australia (2).
It is also dangerous.
In the rugged terrain covered by tangled vegetation people get lost (3).

GEOLOGY
The Blue Mountains started as a plain wich was uplifted into a plateau and then heavily dissected by weathering.

The plateau rises from east to west, where Mt.Piddington is the highest elevation at around 1200 metres (3900 feet). Despite such unremarkable height the Blue Mountains convey an impression of monumental grandeur.

Even Darwin was impressed when he visited the region in 1836.
In his Geological Observations he remarked:
"... The class of view was to me quite novel and certainly magnificent. ... It is not easy to conceive a more magnificent spectacle than is presented to a person walking on the summit plains, when, without notice, he arrives at the brink of one of those cliffs ... Certainly, the most stupendous cliffs I have ever seen..."

There are sheer drops of raw grey, golden brown and orange rock
250m down (820 feet).
Like battlements they circle enormous excavations of yawning steep valleys.

Darwin again: "... to attribute these hollows to the present alluvial action would be preposterous..." He suggested subsidence. But Darwin was wrong. The Blue Mountains are a textbook example of what a coastal climate with generous rainfall can do over 60 million years.

As every spot on Earth, they are a demolition site.

Threequarters of their original mass have been removed.
A gigantic migration of matter: rock gone somewhere else.

The Blue Mountains are a skeletal landscape.
They don't impress by what is, but by what isn't there any more.

Their base consists of tough material of folded and faulted Ordovician, Devonian and Carboniferous rocks from 470 to 320 million years ago.

They have been metamorphosed, sandstone into quartzite and shale into slate with granite intrusions (4).
This base is the surface of the old Lachland Fold Belt, on which the straight sedimentary layers of the Sydney Basin grew. The first of these were marine sediments which became mudstone and shale.
When that ocean retreated it left alluvial flats in deltaic surroundings, covered by lakes and swamps. They produced today's thick Permian coal measures, with a bit of shale on top (4). These "Illawarra Coal Measures" reach a maximum thickness of 231 metres (760 feet) in the western Blue Mountains (5). They were deposited between 280 and 240 million years ago.The coal seams lie in a straight line behind the thickly vegetated slopes down in the valleys.

Above that junction tower those awesome perpendicular cliffs. The soft shale/coal is easily hollowed by the weather. It undermines the sandstone mass on top. This is divided by widely-spaced vertical joints.

When undermined sufficiently, huge chunks of rock shear off. It's this generous spacing of joints which gives the cliffs that unscalable fortress-like look. A smaller spacing would let the rock crumble in bits and pieces.

The second sedimentary layer in the Sydney Basin is the Narrabean Sandstone, intermixed with bands of conglomerate and red/grey/green shale (see also Sydney Basin). It was laid down during late Permian and early Triassic times and might have reached a thickness of 800m (2625 feet) (Herbert 7). Today it is the top layer in the west (see photo) where the Blue Mountains are highest. But this elevation is due to the lift of the Lachlan base underneath, while the Narrabean Sandstone is actually thinnest here with only 150 metres (500 feet) near Mt.Victoria. It adds in height towards the east where it reaches 656 metres (2152 feet) at Kurrajong Heights (5)

The slightly younger Triassic Hawkesbury Sandstone is the third stratum of the Blue Mountains and begins to overlay the Narrabean one about halfway through the mountains, near Linden. It becomes increasingly more massive towards the east. While there are 52 metres of
it (172 feet) at Mt.Tomah, it has grown to 244 metres (800 feet) further east at Kurrajong Heights (5).

It continues under the Cumberland Plain through a dip
in the basin, then rises again into the magnificent ocean cliffs. Sydney is built on - and largely by - the Hawkesbury Sandstone.
Palaeocurrents suggest that the sediments of this quartz-rich sandstone were swept in from the south/southwest. The sandstone's source rock are granites, which underly the Blue Mountains as the Lachlan base and are exposed further west as the Bathurst Granite. An erosional mix from the Southern Highlands was added to this when the Lachlan Fold Belt dipped northwards. But there remained a mystery component. Recent research by Dr.Keith Sircombe from the Research School of Earth Sciences at the Australian National University has identified it as one found also in Antarctica. It sems, that in late Permian/early Triassic times <> 230 million years ago a mighty river must have swept north all the way from Antarctica when that continent was still part of Gondwana (6).

Both sandstones used to be topped by a soft shale of the Wianamatta group. It runs still under the eastern plain right up to Sydney, but on the Blue Mountains this layer has been mostly eroded (see also Sydney Basin).

The sandstones and shale were laid down level-bedded marking tranquil times. They were deposited during the Permian and Triassic periods ending about 230 million years ago. Then follows a huge time gap like geological amnesia. There are no deposits throughout the Jurassic and the Cretacious until the late Tertiary. It is estimated that 4 kilometres (2.5 miles) of sediments would have been laid down during this time, yet, there is no record of it. Erosion must have kept pace with sedimentation (7). This gap of about 200 million years is closed by a layer of basaltic lava which poured over the land between about 14 and 18 million years ago. Much of this basalt has been eroded, only caps have remained on the tops of several mountains: Hay, Tomah, Banks, Wilson and Irvine. On Mt.Tomah the basalt cover is still 80m thick (262 feet), 50m on Mt. Banks (164 feet) (8).

The lifting of the western section of the Sydney Basin into a plateau that became the Blue Mountains was initiated by the upheaval the opening of the Tasman Sea caused, beginning 86 million years ago. During this process a chunk of land broke off the edge of Australia and drifted eastward. It ended up as New Zealand, New Caledonia and a splatter of islands with the rest now a submerged plateau called the Lord Howe Rise. Relieved of the extra weight eastern Australia between Victoria and southern Queensland went through a long period of tectonic realignment expressed by a series of uplifts. These together are now called the Kosciusko Uplift (9). It continued until 2 or 3 million years ago. It formed the Australian Alps. The most significant lift in the Blue Mountains area occurred around 60 million years ago. Today's formations are the result of weathering processes since then.

SIGHTS OF INTEREST
The most picturesque features are situated close to the Great Western Highway between the settlements of Wentworth Falls and Blackheath. Most are easily accessible, some need determined climbing.Wentworth Falls has preserved the Darwin Walk right to the cliff edge, where the great man was thrilled in 1836. There is a network of walking tracks for every capacity and all of them thrilling.

The most popular formation is the Three Sisters at
Echo Point in Katoomba. Here water has seeped into vertical joint lines and washed the rock away, leaving just three columns standing.
They are an impressive one hundred metres (328 feet) of barren rock before the first line of trees.
There are vestiges of more sisters long ago, and the remaining three won't last forever.
A bit over 900 metres (2950 feet) tall they are slimming progressively.

Echo Point is the centre around which radiate major tourist attractions.
There are walks, there is the Giant Stairway with 800 steps for the energetic, and there is the Scenic Railway.
In the old mining days it used to transport coal up from the valley. Now it transports tourists down 300 metres
(948 feet) to the bottom of Jamison Valley - the steepest railway incline in the world. And there is the Scenic Skyway,
a suspended gondola gliding in dizzy 450 metres (1470 feet) over the same valley.

Blackheath, a further along the highway, has several lookouts in spectacular scenery. The Govett Leap Falls at over 300 metres (948 feet) down are the largest in the Blue Mountains.

If you have a 4x4 try to make it to Hanging Rock, perhaps the most impressive spot in the mountains. It's a dicey track for conventional drive vehicles depending on what the weather has been doing.

A lesser known jewel in this area is the Wind-eroded Cave, nature's miniature work compared to the large-scale drama of the cliffs. A combination of the right rock material facing the right direction has let winds whip rain into crevices of the rock. Then chemistry and physics went to work. Minerals reacted with moisture and the rock became weak. Salt crystals were drawn to the surface where they expanded and broke the rock apart. Wind blasted the crumbs away. All this is a process of millimetre by millimetre into the softer sections of the rock while the stronger bits hold out a little longer. The result of this Honeycombe Weathering is an intricate ornamental creation.

The Great Western Highway runs through a multitude of villages merged into the City of the Blue Mountains, with Katoomba as its centre.
By contrast, the Bell Line of Roads to the north winds through a sparsely populated mountain scape. Here, a stop at Pierces Pass is a must. After an easy kilometre walk from the parking lot one arrives at the edge of an abyss. Stare 600, 700 metres down into Grose Valley, that awesome crooked gash.

It's not only vertigo which can be overpowering at thisspot, but also thinking of forces which heave up a chunk of Earth, and then destroy it again.

Condense some million years into a moment and listen to drama Earth, to jackhammers and bulldozers and draglines scooping out this yawning canyon.

Rocks are active. More active than we are, because they have more time than we have. They had 60 million years to get into shape.

Another interesting stop along this road is the Mt.Tomah Botanic Garden, splendid and famous (10).

The most prominent tectonic feature is the Lapstone Monocline.
It forms the eastern boundary of the Blue Mountains and runs for 160 kilometres (100 miles) like a wall in a north/south line. A mighty fold it rises suddenly out of the plain. There are few foothills. At Kurrajong Heights the Hawkesbury Sandstone - top layer on the Monocline - is 600 metres (1970 feet) above its continuation down on the plain (4).
86 million years ago the region of the Monocline might have been level with the Sydney Cliffs. Then the uplift of the Blue Mountains began and probably ended at a height difference of one thousand metres. Hundereds of meters have been eroded from the top since. The corresponding layers down on the Cumberland Plain are thicker than on the plateau. The rise was so gentle and drawn out that the Nepean River could keep its bed. It cuts through the Monocline and was able to dig down at the same speed as Earth heaved up (11). But the stress of this heave made the strata behind the fold break and slip down as a fault. Today that dip in the road lets car engines cool again after the steep climb from the east. Surprisingly, several faults along the way suggest that this feature was pushed up due to compression from the north, and not due to a mighty push from the east, which looks to be the more obvious (12).
The details of the geological genesis of this feature remain quite controversial guesswork. (For various hypotheses see: Sydney Basin). The Rickabys Creek Laterite on top of the rise is believed to be the same as sediments on the Cumberland Plain. This might date the fold's creation some time after this sedimentation. However, its heavy laterisation makes accurate dating impossible, except that it belongs somewhere in the Tertiary - a pick of some
60 million years (12).

FIRST CROSSING
For the first 25 years after white man's arrival the mountains proved to be an unbeatable barrier. They squeezed the growing young colony into the straitjacket of a narrow coastal strip. All attempts to find a passage through the mountains by following western tending valleys ended in dead ends closed by forbidding cliffs.
Governor King at the time: "...a confused and barren ... assemblage of mountains with impassable chasms in between. Any endeavour to penetrate such terrible barrier would be as chemirical as useless.. " (13). Finally, in 1813, the trio William Lawson, Gregory Blaxland and Charles Wentworth figured out the trick:
the only way to conquer the mountains was over their top by following a ridge. They followed many ridges but everyone terminated "at a deep rocky precipice; and they had no alternative but to return...".

The route they finally found is still
closely followed by today's Great Western Highway. What they had found "...changed the aspect of the colony, from a confined insulated tract of land, to a rich and extensive continent..." (14)

Once on top, the plateau character becomes obvious. There are no spires, no soaring peaks, just a succession of more or less even ridges. Only the few basalt-capped summits stand out as gentle undulations. The ridges form receding walls each one behind a thicker haze of blue. It gave the mountains their name and is caused by the Rayleigh effect. The leaves of gumtrees exude minute droplets of ethereal oil into the atmosphere. Together with tiny dust particles and moisture they scatter the short waves of the spectrum, which are the blue ones. On warm hazy days the air around the mountains catches the blues while the rest of the light travels on.

FLORA
Sandstone under generous rainfall produces poor soils with rapid drainage.
The ridge tops and northern aspects suffer great heat in summer while winters in the Blue Mountains are severe with occasional snowfalls.
The result of this lack of nutrients under harsh conditions is a specialised flora of great diversity displaying sensitive adaptation to slight changes in soil type and aspect. The general adaptation was scleropmorphy ( hard and thick leafs) with a dominance of eucalypts. They are fire-adapted. The Greater Blue Mountains are "...one of the most fire-prone regions in the world" (15). A varied fauna has followed the diverse flora. For a description of some of the flora and fauna see
www.bluemts.com.au/ecotourism/nature/default.htm .

Open forest on the upper slopes is common. The tract of unspoiled tall Blue Gum forest at Blackheath is a treasure.
Sparse woodland might change into thick brushwood on the ridge tops depending on aspect and exposure. Where erosion has produced a soil mix of shale and sandstone the vegetation becomes dense and quite impenetrable.There are wildflowers and flowering bushes. There are "valley swamps", recognisable from afar by their lush green vegetation; and there are "hanging swamps" on terraces where underlying shale or mudstone makes for poor drainage.
These swamps harbour a great plant diversity. They are a "rich ecological community with known 195 plant species, many of them rare. The Royal Botanic Gardens has identified the distinctiveness of the Blue Mountains swamps as the only place in the world where these plant species grow together" (16).
At the border between sandstone and impermeable shale water dribbles out among a thick profusion of ferns, sedges and other hydrophytes.
Hanging swamps filter and household water. They release it sowly even during hottest summer. They grow on a peat base which was laid down about 10 000 years ago. If that dries out the swamp collapses and can't be rejuvenated. Today, these swamps are threatened by urban sprawl.
The cool niches of some gorges, where fire can't reach, harbour tracts of rainforest. They are descendents of Gondwanan vegetation from a time when Australia was still linked to Gondwanaland around 50 million years ago. And the family of the Wollemi Pine, thought to be a fossil, was discovered in September 1994 as still alive and healthy at a remote place. Its line is estimated to go back between 90 and 200 million years. Consequently, the Wollemia nobilis is also called the Dinosaur Tree (17).
The Wollemi National Park has another distinction: its 361 000 hectares (3 610km² - 1 400 miles²) represent
"the largest eucalypts forest wilderness in the world" (15).

"The Greater Blue Mountains provides an outstanding example of the dynamic interactions between eucalypt trees, its species-rich shrubby understorey, environment and fire. The eucalypt forest types range from those that co-exist with rainforest where fire is rare, to mallee (multi-stemmed) eucalypts which co-exist in heath lands where fire is frequent. There is no doubt that the Blue Mountains contain the world's most outstanding representation of eucalypt-dominated plant communities" (15).

Professor Jamie Kirkpatrick/University of Tasmania who prepared the case for listing on the World Heritage register:
"If you were to pick one area to demonstrate eucalypts in terms of extend, integrity and diversity you would choose the Greater Blue Mountains" (15).
The flora of the Blue Mountains is characterised as a "complex of types" (9+18).

For at least 14 000 years the Blue Mountains have been inhabited by Aborigines. The World Heritage area contains some 700 Aboriginal occupation sites, rock shelter paintings and platform engravings (15).

The Greater Blue Mountains were listed on the World Heritage register for their complex flora which has remained in its pristine state. Not mentioned was the wild scenic grandeur of the mountains. Yet, it was the terrain's very ruggedness which has kept this wilderness raw and unspoiled despite being on the doorstep of the large and expanding metropolis Sydney, population 4 million.

For designated camping areas within the Greater Blue Mountains see:
http://www.nationalparks.nsw.gov.au/parks.nsf/CampingContent/N0004?OpenDocument&ParkKey=N0004&Type=K

Sources:

1 http://whc.unesco.org/en/list/917 for inscription criteria and a brief description of the park.

2 see Webster's Encyclopedia of Australia

3 for extensive walks updated maps can be obtained from the Department of
Lands and Water conservation in Sydney (02-9228 6360)

The NPWS (National Parks and Wildlife) Visitor Centres cum shops are excellent for information, maps and a variety of reference books. They also offer a choice of tours guided by rangers. Also available is the leaflet "Camping in the Blue
Mountains, Kanangra-Boyd and Wollemi National Parks".
The Visitor Centres are located at:
NPWS Heritage Centre
Govetts Leap Road
Blackheath - 2785 / phone 02-4787 8877

Hartley Historic Site  Hartley - 2790 / phone 02-6355 2117

National Parks Shop Oberon 38 Ross Street
Oberon - 2787 / phone 02-6336 1972

Bowman's Cottage 370 Windsor Road
Richmond - 2756 / phone 02-4588 5247

Visitor Centre at Glenbrook and at Echo Point in Katoomba

4 "Layers of Time - The Blue Mountains and their Geology"
New South Wales Department of Mineral Resources

5 "Geology of the Western Blue Mountains"  R.Goldberg, 1969

6 Australian National University

7 "The Sydney Basin" Science Press 1979  Branagan / Herbert / Langford-Smith

8 "A Field Guide to the Sydney Bushland"  Alan Fairley

9 "The Future Eaters"  Tim Flannery

10 http://www.bluemts.com.au/mounttomah

www.npws.nsw.gov.au/parks lists the locations of the best lookouts and the many different walks you can take.
It is the site of the New South Wales National Parks and Wildlife Service. Find Blue Mountains National Park under "Sydney and Surrounds".

11 www.vnc.qld.edu.au/enviro/bluemtns/blue-b.htm

12 New South Wales Department of Mineral Resources

13 from "Australia: World of Difference"  John Béchervaise

14 Journal of Gregory Blaxland, 1813

15 www.colongwilderness.org.au/bluewh.htm

16 http://www.bluemountains.org.au

17 http://www.rbgsyd.nsw.gov.au/science/hot_science_topics/wollemi_pine
This site abounds with facts and figures about this botanical rarity.

18 www.hawkesbury.net.au/nhwgg/overview/geology.html