Hello and welcome to our first date!
Some people like to tour breweries, others prefer to hunt down hole-in-the-wall eateries. Me? I like to look at rocks. This blog is dedicated to exploring relationship while admiring the scenery. I'm sure, in between poorly focused pictures of my rockpick, you'll learn plenty about my travels and the geology I encounter as I go. So without further ado I present, our first date:
Organ Pipes National Park (-37.667475, 144.766318) was the first National Park established due to geological formations in Victoria. The land used to be a sheep farm and has been since been rehabilitated. n other words, the local volunteers have gotten rid of all the weeds, encourage the wildlife and, most irritatingly, grown plants to cover up the outcrops. The park features a number of walks but four main geological attractions, three of which are available to the general public. The first, the organ pipes, are naturally occurring columnar basalt structures that look like, you guessed it, organ pipes. These form when the basaltic flows fill up a depression. The lava then cools from the top down, contracting as it goes. This creates vertical cracks which split into almost 120 degree angles (triple junction anyone?). Weathering and slight decompression create horizontal fractures resulting in columns that appear to be stacks of edam. Flows cool at different rates and in different directions creating a range of column stacks. Such structures should always be appreciated with an appropriate bottle of wine.
The second outcrop on the menu is the Rosette Rock - a radial igneous formation. Formed from the same process as the Organ Pipes, the radial nature of this formation suggest it was either a slowly cooling lava tube or the lobe of a flow. Either way, decidedly beautiful.
The third remarkable geological feature of this national park is one most people can't find, don't care about and actually shouldn't climb the hill to look at. We, being geologist, simply had to oggle this rare occurance.
The basal contact of the basalt flow over the Silurian mudstone. The mudstone has metamorphosed into hornfels (white). As you can see from the scale, this process produces very little hornfels. The straight / clean contact between the two rocks confirms that the mudstone had been lithofied prior to the lava flow. This outcrop is exciting because when mapping in Victoria, it's so rare to actually SEE the contact.
I highly recommend picking up a nice picnic and setting out to see this National Park. We had lunch on the tessellated pavement with a babbling brook at our feet. The company was delightful, the rocks impressive and the weather was great (for Melbourne anyway).
Posing with some Thrombolites near Perth. May 2012. and yes, that is geology cake on my shirt.
