Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/632397
Bill Langer is a consulting research geologist who spent 41 years with the U.S. Geological Survey before starting his own business. He can be reached at Bill_Langer@hotmail.com CARVED IN STONE 44 AGGREGATES MANAGER / February 2016 "These hills…are remarkable for the singular form of their elevation, which very much resembles a glass house, and for this reason I called them the Glass Houses." Captain James Cook, May 17, 1770 B ack in 2004, my wife, Pam, and I had the pleasure of visiting Queensland, Australia, where I was a keynote speaker at the Annual Conference of the Institute of Quarrying. While we were there, our hosts and friends, Andy and Jo Ste- phens, showed us around the Queensland countryside. One fascinating place we visited was a tropical rainforest at Mary Cairncross Scenic Reserve. Andy cautioned us about leaches and ticks, both of which live in the rainforest. As if to prove his point, while Andy was walking through the forest, a tick took up residence on his bum. But that's another story. The topic of this article is the Glasshouse Mountains, a group of 11 hills that we viewed from Mary Cairn- cross. Captain James Cook spied them in 1770 as he sailed his research vessel, HMS Endeavour, up the coast of what is now Queensland. The Glasshouse Mountains have been, and continue to be, of spiritual significance to the aboriginal people of the region, including the Gubbi Gubbi people. Accord- ing to Gubbi Gubbi legend, the mountains are a family. Mount Tibrogargan is the father, Mount Beerwah (the highest peak at 1,824 feet) is the mother, and the other peaks are the children. One day, Tibrogargan saw the ocean flooding the coast, and he fled inland with his family. Tibrogargan told his son, Coonowrin, to help Beerwah and his sib- lings move to safety. Coonowrin was afraid and ran away. When his father found him, he hit him on the back of the head, resulting in Coonowrin's crooked neck. Tibrogargan was ashamed of his son's cowardice and turned his back on him, never to look on him again. However, the mountains didn't form quite like the legend says. Sixty five million years ago, Australia was further south than today, and still part of the ancient super-continent of Gondwanaland. Much of Australia was covered in tropical rainforest simi- lar to that at Mary Cairncross. Eventually, Australia separated from Antarctica and began drifting northwards. About 29 million years ago, southeast Queensland moved over a 'hot-spot' in the Earth's mantle resulting in prolonged vol- canic activity. Volcanoes spewed out lava flows, building up broad, gently sloping plains. A few million years later, magma was forced upwards through the older rocks, making large bulbous plugs and laccoliths, and filling volcanic necks. After millions of years of erosion, the surrounding softer sandstone rocks were worn away. The more resistant volcanic rocks are now exposed as the steep sided peaks of the Glasshouse Mountains. Some of the older lava is quarried today for aggre- gate, but much of the older lava was weathered into fertile soils that enable rainforests like Mary Cairncross Scenic Reserve to re-establish and thrive, ticks and all. This brings us back to Andy's bum. We got to see the tick only after his wife, Jo, had carefully removed it. What a relief! A geological wonder. The Glasshouse Mountains The Glasshouse Mountains were formed as the result of prolonged volcanic activity followed by millions of years of erosion. A quarry in the lava near the Glasshouse Mountains with Mount Tibrogargan in the background.