Darling Scarp
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The Darling Scarp (previously known as the Darling Range or Darling Ranges) is a low escarpment running North-South to the East of the Swan Coastal Plain and Perth, Western Australia.
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[edit] History
The original inscriptions from maps of the 1830s show "General Darlings Range"; later it became Darling Range, and only in the late twentieth century did it become known as the Darling Scarp. In the late twentieth century it was still being named the Darling Range, despite common understanding of it being an escarpment. Also there was (and still is) a tendency to identify the locations on or behind the scarp as being in or on 'Perth Hills' or 'The Hills'.
Early traverses were by explorers of the 1830s and the most commonly known is that of Ensign Dale, who appears to have gone from the Guildford location, to the south side of Greenmount Hill and up through the Helena Valley.
[edit] Geology
The Darling Scarp is the local expression, in the Perth area, of the extensive Darling Fault, a major and ancient geological discontinuity separating the Archaean Yilgarn Craton in the east from the younger Pinjarra Orogen and overlying Phanerozoic Perth Basin to the west. The Darling Fault is exposed for over 1 000 km, from the area east of Shark Bay, to the southern coast of Western Australia east of Albany.
The Archaean granites and gneisses of the Yilgarn Craton form the high ground of the Perth Hills and can be observed in road cuts, with good examples in the Mundaring Weir area. The only exposed sediments of the Perth Basin, west of the fault, are of Cenozoic age, and comprise the material such as sandy limestone, travertine and dune sand on which the city of Perth is built, including sand dunes of Pleistocene age formed during the last Ice Age.
[edit] Climate effects
Often the Bureau of Metereology identify different weather for 'the hills' in comparison to that of the Swan Coastal Plain
Also, in traditionally hot summers, strong easterly winds travelling across the scarp have presented serious issues for planes using the Perth Airport due to the alignment of the runways. A documented accident in 1999 involving wind shear from the scarp is at the Perth Airport article.
[edit] Landuse conflict
The Darling escarpment has had over the last hundred years been exploited for stone quarries, Forestry and Bauxite Mining. Extensive timber railways and timber mills and the supporting communities existed along the escarpment due to the high quality jarrah forests.
[edit] Water supply
In the early twentieth century, most of the main rivers flowing off the escarpment had mainly been utilised for dams for water supply.
The dams that exist on the scarp, or slightly inland include: Mundaring Weir (on the Helena River), and the Canning Dam (on the Canning River).
The scarp also defines the easternmost limit of the various aquifers present in the Perth Basin sediments, most notably the Southwest Yarraadee Aquifer. The scarp forms adivide between the hypersaline groundwaters typical of the Yilgarn Craton basement from the fresh groundwaters of the Perth Basin. Some dams along the scarp are contaminated by seepage of saline water from the granite into the base of the dam's water column and must be periodically flushed to preserve water quality.
[edit] Rock quarries
Also in the early to mid-twentieth century numbers of rock quarries existed on the edge of the escarpment - visible and affecting both the aesthetics and the environment of the escarpment.
In the area where the Helena River emerges from its valley to the sandplain, there are still four quarries evident, despite being unused for fifty years or more.
- Bluestone (1850s name), later known as Greenmount Quarry (1850s to 1920s), at Greenmount Hill west side of Greenmount National Park.
- Mountain Quarry (now usually signed as Boya Quarry), south of Greenmount Hill, which ceased operation in 1963.
- Fremantle Harbour Works Quarry (sometimes, C. Y. O'Connor's Mole Reconstruction Quarry, and later known as the Public Works Quarry), now Hudman Road Amphitheatre at edge of Darlington - Boya localities border, operated from the 1900s to the 1930s.
- Statham Quarry at Gooseberry Hill at northern edge of the Kalamunda Zig Zag formation.
There have also been visible quarries on the scarp in the Gosnells and Herne Hill areas.
Legislative restrictions upon such developments were initiated in the late twentieth century to prevent further visible scars on the western face of the scarp.
[edit] Railways
- The Eastern Railway first traversed the Darling Scarp in the 1880s along its first route through Greenmount (where three of the above quarries later were able to utilise the railway).
- By the 1890s the second route passed through Swan View Tunnel and John Forrest National Park.
- In the 1960s the third route utilised easier grades through the Avon Valley
- The Kalamunda Zig Zag or Upper Darling Range Railway ran up the southern steep side of the Helena Valley entrance until 1949.
[edit] Bauxite mining
In the late twentieth century, the proving of bauxite deposits correlating to the extensive Jarrah Forests saw wide ranging protests against the proposals to mine the forests.
The lengthy process of protest forced the government and miners to check their original proposals, and wide ranging processes to guard segments of the Jarrah Forests from mining ensued.
[edit] Dieback and fire
Also in the late twentieth century, dieback effecting Jarrah timber in particular infected large tracts of the forest. Currently only the restriction of vehicle access has proved effective in slowing the spread of this disease. This gained greater acceptance and publicity through the decision to allow Rally Australia to operate along services roads provided that the vehicles had a thorough wash including the under carriage at the end of each stage.
In late 2004, the largest bushfire in the Northern Jarrah Forest for at least 100 years has created significant issues for the forest as well. As a result of this fire intensity the Government increase the volume of controlled burns along the entire escarpment to reduce the build up of flammable materials.
In the early 2000's Greenmount National Park, and John Forrest National Park have been repeatedly burnt by bushfires - in most cases through suspected arson.
[edit] Current activity
The escarpment is currently the site of a number of approved mines of bauxite (or Aluminium ore), which are mined by the company Alcoa along with others. The bauxite mines (and rehabilitated areas after mining) have erased all the evidence of the networks of the timber railways.
[edit] Suburbs on the Scarp
The localities or suburbs on the 'edge' of the scarp are those that sit at the western edge of the scarp, and in most cases command excellent views of the Swan Coastal Plain:
The suburbs near Midland andd Kalamunda are often referred to as Perth Hills
Near Midland, Western Australia:
Near Kalamunda, Western Australia:
Near Armadale, Western Australia:
[edit] The future
The potential for further landuse conflict exists in the presence of unrelinquished mining leases over large tracts of the escarpment; plans by Governmental operations in Forest reserves; water authority sensitivity towards access to its water catchment areas; bushfire control measures; and demands for further intensification of urbanization on the escarpment.
[edit] Darling Range Regional Park
A network of reserves of crown lands on the escarpment have been connected into a regional park to maintain and conserve parts of the escarpment.
In most cases the reserves or parks had individual names prior to being incorporated into the larger park, for example the Serpentine National Park, John Forrest National Park and the Greenmount National Park, or were simply known as State Forests (eg State Forest No.42).
[edit] References
- Bean, Alison. A brief history of the Darling Range : for the Department of Planning and Urban Development. Perth, W.A. : The Dept., 1993. Darling Range Regional Park supplementary report ; no. 4. ISBN 0730953041
- Blainey, Geoffrey. White gold : the story of Alcoa of Australia St. Leonards, N.S.W. : Allen & Unwin, 1997. ISBN 1864483555
- The Darling Scarp : a natural entity: proceedings of symposium held at the Geography Department of the University of Western Australia, November 1969 Perth, W.A.: Nature Conservation Council of Western Australia, 1970
- Department of Planning and Urban Development, Western Australia. The Natural resources of the Darling Ranges Perth, W.A. : The Dept., 1993. Darling Range Regional Park supplementary report ; no. 2. ISBN 0730953025
- Murphy, Mike. ( Coles, Helena - editor) Jarrahdalians : the story of the Jarrahdale Mine Booragoon, W.A. : Alcoa of Australia, 1998. ISBN 064636670X
- Myers JS (1992) Pinjarra Orogen, in Geology and Mineral Resources of Western Australia: Western Australia Geological Survey, Memoir 3, 77-119.
- Schur, Basil. Jarrah forest or bauxite dollars? : a critique of bauxite mine rehabilitation in the jarrah forests of southwestern Australia Perth, W.A. : Campaign to Save Native Forests (W.A.), 1985. ISBN 0959744975 (pbk.)
- Watson, Lindsay The Railway History Of Midland Junction : Commemorating The Centenary Of Midland Junction, 1895-1995 Swan View, W.A : L & S Drafting in association with the Shire of Swan and the Western Australian Light Railway Preservation Association, [1995]
