In the heart of the Gawler Ranges is the Kolay Mirica Falls. Kolay Mirica Falls is one of the best places in the Gawler Ranges National Park where you can explore the organ pipes – unique volcanic rock formations. These columns are made from the volcanic rhyolite, formed after volcano erruption some 1500 million years ago. Ash and lava created a solid rock up to 1500 meters thick, which after the cooling formed what we call now as organ pipes. The falls have formed when an area of softer rock has weathered in the rhyolite formation.
Rhyolite is an igneous, volcanic rock, of silica-rich composition. Rhyolite can be considered as the extrusive equivalent to the plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Rhyolites that cool too quickly to grow crystals form a natural glass called obsidian. Slower cooling forms microscopic crystals in the lava. The cause of the organ pipe structure resembling huge crystals is subject to much scientific discussion.
Your earthscience tasks to log this Earthcache are as follows.
1. What is the ratio between the volcanic event at Gawler Ranges and Mount St Helens?
2. At the second waypoint estimate the diameter of the crystals?
3. Determine the average number of crystal sides.
4. (Optional) Submit a photo of yourself with the crystals.