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Introduction
The Blowhole, near the Loch Ard Gorge, is an example of a spectacular rock formation caused by multiple erosional forces.
The limestone along this coastline was formed around 20 million years ago when the sea level was much higher than it was today, with the shoreline at the time being as far inland as Hamilton and Ballarat. Over a long period of time, marine animals' skeletons and calcium-rich algae were laid down to create layer upon layer of this soft rock.
Around 5 million years ago, the sea level dropped and exposed a flat plain extending all the way to Tasmania, and more recently, the sea level rose again to it's present level.
The flat-layered limestones seen in the present coastline vary in hardness and as a result weather and erode at different rates. More rapid rates of erosion also occur along deep vertical cracks (known as joints) that run south-west to north-east throughout the limestones. The location of these joints through the rock has strongly influenced the position of gorges and inlets along the coast.
Rainwater seepage and wave action constantly attack the coastline and exploit weaknesses, such as the predominant SW/NE joints, and this is also the case with the cave that has formed the Blowhole.
The Blowhole is connected to the sea by a long and narrow tunnel. When heavy seas are running, waves compress air trapped in the tunnel and enter the cavern with a loud roar. The confined space concentrates the energy of the wave action and compressed air, and eroded material carried by the waves increases the rate of erosion dramatically.
The Blowhole itself was formed when rain seepage from above eroded and weakened the cave's roof and caused it to collapse into the cave below creating an opening to the sky some 50m long by 20m wide. The cave continues on the inland side of the Blowhole and continues to grow in the direction of the joints in the rock. Ultimately, the cave will grow to a point where all of the roof of the cave will probably collapse forming yet another gorge on this spectacular coastline.
When the Loch Ard was wrecked nearby, 11 bodies of the 52 who perished, were found in the waters below, and the water glowed an eerie purple light from the phosphorous matches washed in from the ship's lost cargo.
This Earthcache
In order to log a find on this earthcache you will need to perform the tasks below. Answers to questions are required to be emailed to the cache owner, and the photo must be uploaded with your online log. Do not give away the answers to the questions in your online log. Failure to supply the answers by email, or to upload the required photo with your log, and your log may be deleted.
Do not visit this earthcache at night - you will not be able to see anything, and therefore you won't learn anything. You also will not be able to take the photograph that is a requirement for logging the earthcache.
1. From the information panel at the published coordinates, how far inland does the cave extend from here?
2. Take a photo from the published coordinates of the blowhole, and including your GPS unit, to prove your visit. An example photo is shown below. Your photo must be uploaded with your online log.
3. At WP2, why should you "keep out of this area"?
Please stay on the tracks - there is no need to leave them for any stage of this earthcache. And remember, "take nothing but photographs, leave nothing but footprints"!
You can log this cache straight away after you have emailed your answers to the cache owner, no need to wait for confirmation. Please include the name of this earthcache in the email - you'd be surprised how many people forget. Also, when contacting us with answers, if you want a reply, please include your email address. Any problems with your answers we'll be in touch.
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