Mount Pelion West and Wildflowers, Overland Track, Cradle Mountain-Lake St Clair National Park, Tasmania
The plateau of central Tasmania is dominated by the great extent of dolerite lava flows that have then been exposed, and sculpted by glacial ice sheet that moved south to north leaving erratics and moraine on the north coast and in Bass Strait. The cliffs and summit of Mt Pelion West reveal the dolerite, which on the summit is a field of large irregular boulders which makes a traverse very difficult. The geology of Tasmania is complex, with the world's biggest exposure of dolerite, a mafic subvolcanic rock similar to basalt .
Dolerite:
A major intrusion of dolerite occurred in the Jurassic. This was a widespread phenomena extending over one third of Tasmania, and possibly more in the past. This intrusion also affected Antarctica, Argentina and South Africa at c180 million years ago. Three to five million cubic kilometers of magma were intruded overall, being the planet's fourth largest known magma intrusion.
Tasmania has the largest exposure of dolerite in the world of 30000 km2 and a volume of 15000 km3. In Tasmania the rock is characteristic of many mountains with its columnar joining appearing in cliffed escarpments. The composition is 40% plagioclase, 20% clinopyroxene, 20% quartz, 5% ilmenite and small percentages of potassium feldspar and amphibole.
Most of the intrusions were in the form of sills up to 500 m thick. But there are also stepped sills, inclined sheets, cones and some dykes. On the Central Plateau mesa and peaks appear as remnants in places, and in other places the dolerite remains, extensively.
Glaciation:
While there has been glaciation of Tasmania for eons (having been connected to Antarctica), in the Permian for example, the present landscape displays aretes, cirques, extensive glaciated surfaces, glacial valleys, moraines and a diversity of lakes attributed to glacial sculpting. Late Pleistocene glaciation occurred in the Snowy Mountains as well as in the Tasmanian highlands. Glaciers were extensive in Tasmania where ice caps formed on the Central Plateau and West Coast Ranges, and systems of valley and cirque glaciers formed on surrounding mountains.
Mount Pelion West and Wildflowers, Overland Track, Cradle Mountain-Lake St Clair National Park, Tasmania
The plateau of central Tasmania is dominated by the great extent of dolerite lava flows that have then been exposed, and sculpted by glacial ice sheet that moved south to north leaving erratics and moraine on the north coast and in Bass Strait. The cliffs and summit of Mt Pelion West reveal the dolerite, which on the summit is a field of large irregular boulders which makes a traverse very difficult. The geology of Tasmania is complex, with the world's biggest exposure of dolerite, a mafic subvolcanic rock similar to basalt .
Dolerite:
A major intrusion of dolerite occurred in the Jurassic. This was a widespread phenomena extending over one third of Tasmania, and possibly more in the past. This intrusion also affected Antarctica, Argentina and South Africa at c180 million years ago. Three to five million cubic kilometers of magma were intruded overall, being the planet's fourth largest known magma intrusion.
Tasmania has the largest exposure of dolerite in the world of 30000 km2 and a volume of 15000 km3. In Tasmania the rock is characteristic of many mountains with its columnar joining appearing in cliffed escarpments. The composition is 40% plagioclase, 20% clinopyroxene, 20% quartz, 5% ilmenite and small percentages of potassium feldspar and amphibole.
Most of the intrusions were in the form of sills up to 500 m thick. But there are also stepped sills, inclined sheets, cones and some dykes. On the Central Plateau mesa and peaks appear as remnants in places, and in other places the dolerite remains, extensively.
Glaciation:
While there has been glaciation of Tasmania for eons (having been connected to Antarctica), in the Permian for example, the present landscape displays aretes, cirques, extensive glaciated surfaces, glacial valleys, moraines and a diversity of lakes attributed to glacial sculpting. Late Pleistocene glaciation occurred in the Snowy Mountains as well as in the Tasmanian highlands. Glaciers were extensive in Tasmania where ice caps formed on the Central Plateau and West Coast Ranges, and systems of valley and cirque glaciers formed on surrounding mountains.