AT THE POINT
Degree Confluence 18°S 145°E (Google Earth Image)
Location: This confluence point has yet to be visited. It lies about 1 km east of the road that follows Rudd Creek, about 67 km south-west of Ravenshoe. The nearest town is Mt Garnet, about 38 km north-north-east. The point lies within the Tablelands Regional Council area.
The Landscape: The point lies at an elevation of around 600 m ASL. It is located on a basalt flow of Pleistocene age (less than 1.8 million years) and is in the catchment of the Herbert River.
Point information and photos: The point is yet to be visited.
WITHIN THE DEGREE SQUARE
McBride Basalt Region flows (Ken Granger using Geoscience Australia data)
The Country: The degree square straddles the divide between the catchments, such as the Lynd River, that flow to the Gulf of Carpentaria and those, like the Herbert iver, that flow to the Coral Sea. Elevations range from a maximum of 1150 m ASL in the Great Dividing Range to the north of Ravenshoe to about 400 m in the north west-corner. The large dome of the so-called McBride Basalt Region to the south-west of the point has a maximum elevation of around 1020 m ASL at the summit of Mt Undara.
The volcanoes of the McBride Basalt region are the dominant feature of the landscape in the south-west quarter of the square. It covers an area of about 5000 km2, and is composed of basaltic lava flows erupted from many large and small volcanoes. An older series of basalts, preserved in mesas, are of Late Miocene age (dated at 7.3 to 7.8 million years). Most of the volcanic rocks of the Province were erupted in the interval from the Late Pliocene (2.7 million years) to almost the present day. Numerous volcanic features are evident in the landscape including the crater of Mt Undara and scoria cones such as the Kalkani Crater and Rangaranga Hill. The geological mapping of the area shows 11 distinct basalt sources originating within the overall McBride province.
Of these, it is the most recent group originating from the Undara Crater that has attracted the most attention from scientists and tourists alike. The Undara Lava Tubes date from about 190,000 years ago, in the Cainozoic era, when there was a massive eruption and lava flowed more than 90 km to the north and over 160 km to the north-west. An estimated 23.3 cubic kilometres of lava flowed from the volcano in that eruption. The lava tubes were formed when rivers of lava, confined to a valley, crusted over and formed a roof. Insulated in its casing of solidified lava, the lava flow carried on for many tens of kilometres before draining out, leaving an empty tube of lava. Weaker sections of the roof of the tubes later collapsed to form caves and depressions. More than 50 caves have been found in the area now included in the Undara Volcanic National Park.
Undara Lava Tubes and older volcanic features (Google Earth)
Rangaranga Hill (KG, 2008)
Kalkani Crater floor (KG, 2008)
Tourists in lava tube (KG, 1997)
Interior of lava tube (KG, 1997)
The high country in the north-east of the square, around Ravenshoe, is a mixture of Late Carboniferous age (318 to 299 million years) volcanic rocks and granites. The present-day landscape takes the form of rolling steep-sided hills and well-entrenched streams. Elevations in excess of 1 000 m ASL are common. Residual thermal activity is still evident in the Innot Hot Springs on the road between Ravenshoe and Mt Garnet.
The two areas of high country are linked by a broad ridge of intruded granite, mostly of Late Carboniferous age. This ridge provides the divide between the eastern and north-western flowing drainage. Elevation along this divide is typically around 750 m ASL. To the north-west of the divide slopes are generally low and made up of Quaternary age deposits of alluvium or colluvium. Streams such as the Lynd River and Tate River (a tributary of the Lynd) tend to be well entrenched until they reach the lower country in the north-west.
Drainage to the east of the divide includes the Herbert and Burdekin Rivers as well as smaller streams such as the The Millstream. Most are deeply entrenched and some have significant waterfalls and gorges along their courses through this square. This gives rise to some areas of rugged country.
The vegetation across the square is extremely varied and complex. The indigenous cover over the greatest area an open grassy savannah woodland of medium height dominated by eucalypts such as ironbarks, and Rough-leaved Bloodwoods (Corymbia setose). Ground cover is typically tussock grasses such as Bunch Speargrass (Heteropogon contortus). In some areas shrubs such as Caustic Bush (Grevillea mimosoides) can form thickets in the savannah.
Typical eucalypt savannah country (KG, 2008)
Savannah and vine thicket at Undara (KG, 2008)
Ribbons of emerald-green vine thicket, contrasting with the surrounding dry savannah woodland, mark out the courses of the collapsed lava tubes. The semi-evergreen vine thicket contains distinctive and ancient plants that have strong affinities with Gondwana species. Species found include various figs and the distinctive Broad-leaved Bottle Trees (Brachychiton australis), with massive trunks that serve to store water, Burdekin Plums (Pleiogynium timorense) that produce large edible fruits and White Cedar (Melia azedarach). The dry rainforest also contains the nationally rare, white-flowered, onion vine (Ipomoea saintronanensis).
Caustic Bush on Kalkani Crater (KG, 2008)
Onion Vine, John Beasley
There are also extensive areas of pasture in the western parts of the square and areas of cultivation around Ravenshoe.
The more visible fauna of the area includes various wallabies such as the Antilopine and Common Wallaroos, Eastern Grey Kangaroo and the Red-legged Pademelon. The Echidna and Northern Quoll are also common. The lava tubes are home to several species of bats including the Common Bentwing, Common Sheathtail and Dusky Horseshoe Bats. The dingo is also found across the area.
Broad hectare land use is still dominated by beef cattle grazing.
Climate: The climate across the square ranges from subtropical towards the coast and tropical savannah inland. Both have a winter drought. While the closest weather station to the degree confluence is at Koombooloomba Dam (~65 km to the east-north-east), averages for Mount Surprise Township (just to the west of the square) which are representative of the savannah climate regime, while Herberton is fairly representative of the subtropical regime.
Mt Surprise Township has an elevation of 462 m.
The highest temperature recorded was 42.2°C in November 1965, and the lowest was -2.5°C in June 1963. The greatest rainfall recorded in a year was 1 792.7 mm in 1974, and the least was 242.0 mm in 1902. These and other climate statistics for Mt Surprise can be found at: Australian Bureau of Meteorology, http://www.bom.gov.au/climate/averages/tables/cw_030036.shtml.
Herberton has an elevation of 918 m.
The highest temperature recorded was 38.1°C in November 1990, and the lowest was -5.0°C in July 1958. The greatest rainfall recorded in a year was 2 240.6 mm in 1974, and the least was 1 377.6 mm in 1915. These and other climate statistics for Herberton can be found at: Australian Bureau of Meteorology, http://www.bom.gov.au/climate/averages/tables/cw_031029.shtml.
Extremes of Nature: The area is very much subject to the impact of cyclones. The database maintained by the Bureau of Meteorology shows 49 cyclones have tracked within 200 km of the confluence point since 1906. Six cyclones have tracked within 50 km of the confluence point. They were an unnamed cyclone in January 1910, an unnamed cyclone in February 1929, an unnamed cyclone in February 1945, TC Agnes in March 1956, TC Judy in February 1965, TC Justin in March 1997. Any cyclone that comes within several hundred kilometres can produce destructive winds, heavy rain and flash flooding. On the steeper country the intense rainfall can also trigger landslides and debris flows, especially in creeks in the granite and basalt country. Cyclone information for this area and all of Australia can be found at the Australian Bureau of Meteorology website, http://www.bom.gov.au/cgi-bin/silo/cyclones.cgi.
Cyclone tracks within 200 km of point 1906 to 2006 (Bureau of Meteorology web site)
Floods in the major streams are common during periods of intense rain and river rises can be very rapid. Major floods in the Herbert and Burdekin are common, however in the parts of their catchments within the square, such floods rarely pose a significant threat other than to the road network.
The area experiences between 20 and 30 thunder days per year. Severe thunderstorms can bring destructive winds, intense rainfall that can produce flash flooding and lightning. Storms in the dry winter period can spark bushfires if there is sufficient fuel to promote spread.
Extreme heat is also a serious issue in the west of the square. The climate records for Mt Surprise show that on average (over 21 years of records) the area experiences 59 days a year with temperatures over 35°C and 1 day a year with temperatures over 40°C. Such extreme temperatures can cause heat stroke and death if appropriate measures are not taken such as avoiding strenuous physical effort, keeping as cool as possible and drinking lots of water. Heat waves kill more people in Australia than all other natural hazards combined. Heatwave episodes in the higher country in the east of the square are uncommon.
The National Earthquake Database maintained by Geoscience Australia contains 72 earthquake epicentres within the degree square. The strongest event was a ML 3.5 quake on 6 November 1992 with an epicentre a few kilometres south of Ravenshoe. A smaller ML 3.2 event was recorded about 12 km north of Ravenshoe on 19 June 1950. Of the remaining events, only five had magnitudes of between ML 2 and 3 with the remainder being under ML 2. No damage was reported from any of these earthquakes, though the stronger events close to Ravenshoe would certainly have been felt by people in the area.
The Indigenous Story: The land within the degree square is divided between the traditional country of several Aboriginal groups. In the west the country was home to the Agwamin; on the east the Djirbalngan made their homes; and in the central and southern area the Gugu-Badhun were in control.
MORE INFORMATION WELCOME
European Exploration and Settlement: The first European explorer to pass through the area was probably Ludwig Leichardt in 1844-5 on his expedition from the Darling Downs to Port Essington. He noted in his journal passing through 'young' volcanism, probably referring to the lava fields from the Kinrara field in the south-east of the McBride Basalt region. Edmond Kennedy on his ill-fated expedition from Rockingham Bay to Cape York in 1847 also passed along the eastern side of the square close to the present site of Mt Garnet.
Pastoralists began taking up selections in the area as early as 1861 and by the 1870s mining of tin, gold and copper to the west had brought roads and the telegraph through the area. To the east, it was timber, rather than minerals that brought development. The rich stands of cedar, walnut, mahogany and pine in the rainforests of the Evelyn Tablelands brought loggers and saw millers into the area. Ravenshoe (then known as Cedar Creek) grew as a timber town with several sawmills operating there until the surrounding forests were closed off to logging, being part of the World Heritage Wet Tropics area in 1988. The area was opened up to agriculture in 1903 with dairying a major enterprise. The railway reached the town in 1916 and the name was changed to Ravenshoe.
Mount Garnet, by contrast, was founded on mining. Copper lodes were discovered in the area and mining began in 1896. A smelter was blown in by January 1901. Around that time Mt Garnet rivalled Charters Towers as the largest inland town in the State. A branch railway line from Lappa Junction reached the town in 1902. Both enterprises were the work of John Moffat enterprises. The smelter ceased operation in 1903 but the discovery of tin at Nymbool, a few kilometres to the west, saved the town from extinction. Tin dredging became the mainstay of the town from the 1920s until the 1980s. Zinc is now mined in the area.
The lava tubes of Undara were first recorded in 1891 by geologist A. Gibb Maitland who noted 'tubular caverns' in the basalt and correctly judged them to be formed by the drainage of roofed lava channels. In the early 1960s geologist John Best mapped the area and identified what he termed 'collapsed lava tunnels'. He gave the name 'Undara' to the area from the local Aboriginal word for 'long way'. Much of the early investigation of the lava tubes was undertaken by Tim Griffin whose PhD study covered the McBride Basalt region. The Undara Volcanic National Park was proclaimed in 1992.
The total population of the degree square at the 2011 national Census was 3391. Of this total 860 were living in Ravenshoe and 245 in Mt Garnet. Most of the remainder of the population are spread across the agricultural districts of the north-east corner.
Under 5 years
65 years and over
The gradual decline in population over from 1996 to 2006 was probably due to the decline in the cattle industry because of the prolonged drought.
The Undara Volcanic National Park has become a major tourist destination, though the majority of tourists visit the area during the winter dry season.
Ravenshoe, which is 930 m ASL, boasts as being the highest town in Queensland. It is a service centre for the surrounding agricultural district and is the location for Queensland's first wind power generation farm on Windy Hill. This facility has 20 windmills, each 45 m tall, which have a combined capacity to produce 12 megawatts of electricity, enough to power a town of 3500. The site was commissioned in 2000 and is operated by the Stanwell Corporation, a government-owned enterprise. The town is well served by sealed road access to the coast at Cairns via the Atherton Tableland.
Ravenshoe (Google Earth Image)
Windy Hill wind farm (KG, 2008)
Highest pub in Queensland at Ravenshoe (KG, 2008)
Mt Garnet remains a town focused on mining. The Kagara Zinc Ltd open cut mine is located on the southern side of the town and exploitation of the zinc and copper resource began in 2003. The town is well served by sealed roads to the coast at Cairns and to the south via Charters Towers and Townsville via the Kennedy Highway.
Mt Garnet and the Kagara Ltd zinc mine complex (Google Earth image)
Cattle grazing remains the main broad-hectare land use across the square.
About 1 km off a road that runs along Rudd Creek;
Site not yet visited
Mt Garnet about 38 km to the NNW
Rudd Creek a tributary of the Herbert River
Geology & soils
Pleistocene age basalt flow of the McBride Basalt region
Open eucalypt dominated mid-height savannah woodland
Tropical savannah with a winter drought
Population in degree square
3 053 at the 2006 national census
Extensive sealed and unsealed road network; Windy Hill wind
Undara Volcanic NP, Forty Mile Scrub NP, Kinrara NP, Girringun NP,
Compiler: Ken Granger, 2009
Edited by: Hayley Freemantle
References: various web sites including EPA, tourism, local government and Bureau of Meteorology.
EPA, 2001: Heritage trails of the tropical north, Environmental Protection Agency, Brisbane.
Colin Hooper, 2006: Angor to Zillmanton - stories of North Queensland's deserted towns, Bolton Print, Townsville.
Anne and Vernon Atkinson, 1995: Undara volcano and its lava tubes, self published, Brisbane.