• Introduction: Organ pipe park is part of the Greater Western Volcanic Plains , which is the third largest lava formation in the word . The span of these planes runs from Melbourne to Mt Gambier which is situated in South Australia .
A million years ago , at Mount Holden were keilor Plains are located , The continual flowing lava of lava in molten form over the plains , filled the preexisting valleys and depressions on the land surface , later on cooled and reached a solid state to form basalt , The formations of columns is further explained in the weathering and structural features below
• Weathering: The rock formation showcases the growth of valley incision caused by the down cutting action of the water stream from Jacksons Creek.
Another Cause of weathering can be the growth of plant life on the rock surface which increases humidity between rock imperfections, this can cause chemical and physical breakdown of the surface micro layer of the rock . The saplings budding in a fracture and growing plant roots will apply physical pressure and will provide a passageway for chemical and water permeation.
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Fractures caused because of water pressure due to the brittle nature of the rock can be seen, this is the jointing in the basalt. We walked down the creek path to closely observe the basalt structure and saw a complex joint system, which we believe after further reading happened after the lava solidified into basalt it underwent contraction due to cooling. This shrinkage resulted in tensile strain to be applied on the rock mass, because the upward and downward tension could be put up by the molten elastic rock underneath the crust whereas the horizontal stress caused the outer crust to crack, which resulted to form a joint system and horizontal pipe like structure