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Grant Gibson 
Did you know (as you ascended the mighty Dumgoyne) that the lump you were on is the worn down remnants of a volcanic plug,i.e.,a basaltic plug blocking the vent of an ancient volcano. Relax–it has not been active for about 200 million years. It has a neighbour called Dumfoyne, also a basaltic plug. In fact a
whole line of plugs runs west to east along the north facing Campsie escarpment. The plugs follow the line of what was once a fissure of the Icelandic type which subsequently solidified. Later eruptions broke through weak spots along the fissure to form the above mentioned vents of which Dumgoyne is the first in line. Not a lot of people know that–so there!
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