Box Vale - Undercutting EarthCache

Earth Cache

For part of the way you will be walking along The Box Vale Tramway Walking Track. You will find a fuller description of the tramway on the pages for other caches in the area. For the other part of the way, you will be walking along a fire trail, and then down a long staircase, that takes you to the Forty Foot Falls. Additional information about the falls and maps for the area are available from the Visitors Information Centre in Mittagong.

Mobile phone reception may cut in and out as you descend toward the Forty Foot Falls.

Note, it is also possible to approach GZ following the Red Trail from Lake Alexandra.

Undercutting

A waterfall is a geological formation resulting from water, often in the form of a stream or creek, flowing over an erosion-resistant rock formation that forms a sudden break in elevation or knickpoint.

Forty Foot Falls was created by rainfall runoff that flowed down hills thanks to our friend, gravity. Over time, the rainfall carved a creek and eventually the waterfall you see at the posted coordinates. The waterfall formed at this spot because the sandstone that makes up the lower portion of the waterfall is relatively soft and was eroded more quickly than the harder rock around it.

Some waterfalls become undercut, where the rock wall behind the falls is worn away. When this happens, after the water goes over the edge of the waterfall it falls freely to the ground instead of running down the rock face as can be seen in some waterfalls.

The undercutting increases over time as the water splashes back onto the rock face slowly eroding it. After a while, the undercutting may get to a point where you can walk behind the waterfall.

To claim this cache:

The posted coordinates will take you to the Forty Foot Falls lookout. Unlike most lookouts that provide expansive views of grand vistas, this lookout encloses you in the confined spaces beneath and behind the Forty Foot Falls and has practically no view at all.

1. From the lookout at GZ, estimate the distance the water falls. In other words, how tall are the falls?

2. In addition to the forces that create a typical waterfall undercutting, there is another feature at the Forty Foot Falls contributing to the process. What is that feature and how does it impact the undercutting.

Please send your answers to me via the geocaching website - e-mail or message. The answers to these questions should not be included in your log, nor should your log include spoiler photos. You do not need to wait for a reply from me to log your find.

** Congrats to J+J.au for FTF! **