GLASSHOUSE MOUNTAINS: Matthew Flinders & the Coastal Landforms of SE Australia

Hot Spot volcanoes are found along most of eastern Australia. They are believed to have formed when the portion of the crust containing Australia drifted across a stationary 'hot spot' in the upper mantle below. This caused a sequence of volcanic centres above. The crust of northeastern Australia passed over this spot first, and so contains older volcanoes. Southeastern Australia passed over it more recently, and so has younger volcanoes. As all the hot spot volcanic eruptions finished long ago, only eroded remnants remain today. All these volcanoes, are, of course, extinct. The area of northeastern NSW and southeastern Qld crossed this spot about 20 million years ago; at this time widespread volcanic activity took place at many local centres. This page looks at the Glasshouse Mountains, a spectacular cluster of steep volcanic peaks.
'Glass Houses ... Vis. 15 or 20 leag. ... low woody land' - from Flinders' chart Matthew Flinders used the Norfolk's boat to travel further up the 'river' to gain better access to the 'Glass Houses'. Then, with Bongaree and two sailors, he visited the Glasshouse Mountains on foot. They ascended a 'low' peak [Mt Beerburrum], viewing the main cluster of peaks. They finally arrived at the base of a large peak with a very steep face ... (see below)	Extract from Flinders' chart
The walk to Glasshouse Mountains ' ... [on 26 July 1799] I landed on the west side, as far above the sloop [Norfolk] as the boat could advance; and with my friend Bongaree and two sailors, steered north-westward for the Glass-house peaks. After nine miles of laborious walking, mostly through swamps or over a rocky country, we reached the top of a stony mount, from whence the highest peak was four miles distant to the north-west ... Early on the 27th, we reached the foot of the nearest Glass House, a flat-topped peak ... It was impossible to ascend this almost perpendicular rock ... ' - Matthew Flinders in Terra Australis
The chief peaks of the Glasshouse Mountains are protected, as national parks. However, surrounding them are commercial landuses, including farmland and softwood (pine) plantations. The trees are rapidly growing slash pines, used widely in building products and in many other ways. The rounded mountain on the left of photo is Beerburrum. From the forestry tower at the summit 360° views of the other Glasshouse Mountains and surrounding areas can be obtained.	Photo 1: Panorama looking west from Wild Horse Lookout Beerburrum (left) to Tibrogargan (right)
Matthew Flinders, with three companions, climbed the rounded peak, Beerburrum, and appreciated the view from here. He then approached the base of another peak, with an almost vertical, and unclimbable, cliff face (It is one of the peaks in Photo 1, above).
This scenic area is the product of active volcanic processes millions of years ago (the main eruptions were about 20 million years ago), and the subsequent erosion that removed outer, softer material to expose inner, harder volcanic plugs. These mountains are enjoyed by many, especially photographers, bushwalkers and rock climbers. On the surrounding flatter lands, agriculture (including pineapples, avocados and fruit trees) and native and plantation forestry are important. On a clear day, Brisbane, Pumicestone Channel, Bribie Island, Moreton Island and parts of the Sunshine Coast can all be seen from the tallest of these peaks.	Photo 2: Looking south to the Glasshouse Mountains (Brisbane can be seen in the distance on a clear day) Photo 3: Looking west to the Glasshouse Mountains (Grass tree shown on left side of photo)
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The peak shown is Coonowrin (also known as Crookneck). (see Glasshouse Mountains Story above) It is a 'classic' volcanic plug, formed from magma cooling in, and blocking, the lava tube of a major vent. The original overlying, less resistant material, has been removed by erosion, presumably over millions of years. The rock type is an alkali rhyolite rich in sodium and potassium (known as comendite). It is a fine-grained, tough and light bluish-grey coloured rock, in places containing visible crystals of several mineral types.	Coonowrin Photo 4: Mt Beerwah (left) and Mt Coonowrin (Crookneck) (right)
The Glasshouse Mountains area makes considerable mention of the visit by Matthew Flinders on the Norfolk expedition to 'the northern bays'. A. The plaque (shown right) is attached to a large volcanic rock near the Beerburrum State School (text below). B. The plaque at the roadside rest area (shown far right) offers pleasant picnic facilities, and imparts additional information on Flinders' visit (text below).	Berrburrum ascent Photo 5a: Flinders at Mt Beerburrum 5b: Flinders Rest Area enlarge plaque (above left) (use Back button to return)
A. Lt. MATTHEW FLINDERS R.N. CLIMBED BEERURRUM MOUNTAIN ON 26 JULY 1799 HE DISCOVERED AND MAPPED MORETON BAY BETWEEN 15-20 JULY AND MADE THE FIRST KNOWN INLAND EXPLORATION TO VISIT THE GLASSHOUSES SEEN FROM THE OCEAN AND NAMED BY CAPTAIN COOK IN MAY 1770 ON 26 JULY HE CLIMBED MT. BEERBURRUM AND TOOK SIGHTINGS TO CONFIRM HIS MAPS BUT FAILED TO CLIMB MT. TIBROGARGAN NEXT DAY FLINDERS RETURNED TO HIS SLOOP NORFOLK LYING IN PUMICE STONE CHANNEL MATTHEW FLINDERS BICENTENNARY COMMITTEE BEERBURRUM 26 JULY 1999 B. Lt. MATTHEW FLINDERS R.N. CAMPED NEAR THIS SPOT OVERIGHT 26/27 JULY, 1799. HE DISCOVERED AND MAPPED MORETON BAY AND ITS SIX NORTHERN ISLANDS (15-20 JULY) AND MADE THE FIRST KNOWN INLAND EXPLORATION TO VISIT THE GLASSHOUSES (SEEN FROM THE SEA AND NAMED BY CAPTAIN COOK IN MAY 1770). HE CLIMBED MT. BEERBURRUM AND TOOK SIGHTS TO CONFIRM HIS MAPS (26 JULY) BUT FAILED TO CLIMB MT. TIBROGARGAN NEXT DAY AND RETURNED TO HIS SLOOP 'NORFOLK' LYING IN PUMICE STONE CHANNEL THIS PLATE WAS SET UP BY THE ROYAL HISTORICAL SOCIETY OF QUEENSLAND (PRESIDENT SIR RAPHAEL CILENTO) WITH THE ASSISTANCE OF THE DEPARTMENT OF MAIN ROADS, QUEENSLAND, ON 27 JULY 1963, THE 164th. ANNIVERSARY OF THESE EVENTS.
Mt Beerburrum views: 2002 Photo A Beerburrum, the mountain climbed by Flinders and his small group over 200 years ago, is rounded in shape, and is somewhat easier to climb than the well-known 'pointed' peaks. However, while wearing Royal Navy uniform, and ascending the peak without the benefit of a track or map, the experience must have been a challenging one (especially after the walk from 'Pumice Stone River' where the Norfolk was anchored). Photo B & C give useful advice to present-day walkers who are about to attempt the ascent of Beerburrum.	Photo 6: Mt Beerburrum views
Photo D At the summit is the fire observation tower. The valuable state forests and national parks of the area can be protected by warnings raised on days of high risk (i.e. days with high temperature, low humidity and strong wind). Tower facilities are powered by solar panels on the roof.
Shown is Tibrogargan, the base of which was visited by Flinders' expedition. Due to its rugged nature it could not be climbed then. The present-day track ascends the left (west) side of the mountain. Other Glasshouses are visible on the left (north) of the photo. In the distance is the basalt-capped Mapleton-Maleny plateau.	Photo 7: Looking north towards Mt Tibrogargan (viewed from Beerburrum)
The plateau and the Glasshouses are of similar age (about 25-20 million years) but have different origins. The plateau formed when low viscoscity ('runny') lava erupted from volcanic centres, filling valleys, covering the existing sedimentary rock and eventually forming a gently sloping 'upland'. The Glasshouses are volcanic plugs, formed from lava that intruded into older sandstone. The trachyte and rhyolite rocks of the plugs have a higher silica content than basalt, producing light-coloured, resistant rocks. These plugs cooled underground at a time when the land surface was higher. Over the millions of years since the intrusions, erosion has lowered the general landscape (of softer sandstone) and removing much of the volcanic materials that covered the plugs. Thus today the plugs are exposed. Some of the plugs have developed overhangs and caves near their summits. Several of the mountains (including Beerwah, Ngungun and Coonowrin) illustrate vertical columns formed when the original magma cooled and contracted.
Near the summit of Beerburrum it is possible to consider some of the forces that contribute to the weathering and erosion (wearing down) of the landscape. Exposed rock surfaces are partially covered by algae and lichen. Acidic materials from algae and lichen (and decomposing leaves and grass) can promote the chemical breakdown of rock. Joints (i.e. breaks in rocks) and overhanging 'ledges' collect moisture, which may also speed up rock breakdown.	Photo 8: Rock surface, near summit Mt Beerburrum
Other forces are also involved in wearing down landscapes (including gravity, running water, the freeze-thaw of water, daily expansion-contraction, fire, acid rain).
Photo 9: Signboard (near Beerburrum State School and at Matthew Flinders Rest Area) The signboard draws together important earth science concepts relating to the area.

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