Stairway Falls EarthCache
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Stairway Falls is a spectacular example of the volcanic origins of the World Heritage listed Lamington National Park. This unique waterfall showcases an excellent example of “columnar jointing”. There are other locations where this geological feature can be seen, however these tend to be in coastal locations. There are few places in the National Park itself where one can observe such impressive formations so clearly.
The Lamington National Park was created by massive basalt lava flows from the now long extinct Mt Warning/Tweed Volcano Shield Volcano some 23 to 25 million years ago. Over millennia, the elements have carved the many valleys and gorges radiating away from the volcano’s caldera. Water, wind and rain have eroded away the layers of rock to reveal the basalt columns that you see before you.
When lava cools, it contracts. Hot things generally take up more space than cool things do. So when hot things cool, they get smaller and often crack or fracture. When this contraction occurs, cracks usually appear at centres which are equally spaced (see the below diagram), and a hexagonal fracture pattern will develop. If the contraction is not evenly spaced, then other shapes, such as 5-sided or 7-sided fractures, will occur.
In lava the contraction may not be equally spaced if thickness or composition of the lava flow varies during eruptions. The fracture pattern that forms at the top surface will tend to follow down into the lava as it cools, forming the long, geometric columns you can see here. So, as the lava cools to form basalt, it may crack in a hexagonal (or other) shapes to create columns. These columns form in a variety of sizes. The formation of columns is particularly enhanced by the presence of water during the cooling period as displayed here.
To claim a find for this Earthcache you will need to go to Stairway Falls and answer the following questions:
1. What shape has the creek carved through the basalt above the top of the falls and why do you think this has occurred?
2. Estimate the average diameter of the columns.
3. Estimate the diameter of the pool at the top of the falls.
4. Optional: just to show you were actually there; roughly how far away from GZ is the cave upstream of the falls?
Please email your answers to the COs when you submit your found it log.
Getting to Stairway Falls involves a hard return walk of approx. 12km using a combination of graded and disused tracks, and some rock hoping down West Canungra Creek. Navigation is fairly easy by following the creek downstream approx. 3km from Blue Pool (via the West Canungra Creek circuit). Cross the creek below Blue Pool and locate the old National Park sign which marks the start of the old Stairway Falls track. Some sections of the old track are easy to follow, others not. If you lose the track, keep to the creek.
Take usual bushwalking precautions, ie. appropriate footwear and clothing for off-track hiking, plenty of food and water and always tell someone where you're going. Allow at least 5 hours for the return trip and if it’s hot, take a dip in one of the best swimming holes you’re likely to find.
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