DANGER: DO NOT ATTEMPT THIS CACHE WHEN THE SPILLWAY IS OVERFLOWING!
To log this earthcache, answer the following questions:
1. What is the name of the ocean that covered this area?
2. What water based action caused the rocks to be exposed?
3. From your observations on site, what is the angle of the tilting of the sedimentary layers here?
4. Please include a photo of yourself, your team OR an identifiable object showing the upstream overflow weir wall with your log.
Feel free to log your find straight away but message the question answers to the cache owner within two weeks of your find. Logs without an acompanying photo or without answers being sent may be deleted without notice.
Some Background
In October 2022 this area of Victoria was subject to major rainfall events which caused Lake Eppalock to fill to around 133% of its capacity. This resulted in the Main and also the Secondary (overflow) Spillways to be overflowing in massive proportions. The force of the overflowing water here at the Secondary Spillway (which is physically higher than the Main Spillway) caused a major erosion event, washing away the existing road and also the surface ground that completely covered the sandstone formation that you see before you.
Note the ground level prior to the 2022 overflows indicated by the RED line in the image below.
This video shows the overlows at the time.
An Earthcache Lesson from a layperson
What you see before you are sedimentary layers of rock. They were formed around 450 million years ago when this area was covered by the Paleo-Pacific Ocean. The sediment in the water dropped out of suspension and formed layers at the bottom of this sea. Over millions of years immense pressure changed the sediment layers into rock. The layers are different in texture, colour and thickness due to different types of sediment, minerals and sea life being deposited over millions of years.
But these sedimentary layers are not flat and horizontal. Correct, they are standing up on edge, this resulted from extreme pressures exerted by mountain forming volcanic activity. This caused what is known as folding, tilting and uplifting which changed the plane and flatness that the sedimentary layers were formed in.
- Folding is where once flat layers are now bending or curving.
- Tilting is where the flat layers are tilted at a different angle from the horizontal they were formed in.
- Uplifting is where layers are forced up by various pressures and can include folding and tilting formations.
Over thousands of years these sedimentary layers were covered by more silt and topsoil which was washed away by floodwaters in 2022 to re-expose the rock that is here today.