Congratulations! If you have managed to make it to Steep Point then you really deserve a medal for sitting through all those corrugations, hopefully your teeth didn’t rattle out!
We have made this Earth Cache a quick and easy one, we figure if you have come all this way to the westernmost edge of the Australian mainland you wont want to be worrying too much about technical Earth Cache answers!
Please be vey carful in the area and keep dare devil husbands and curious children on a short tethers!
Apart from the iconic factor of being the westernmost edge of the Australian mainland there is something simply amazing about this area. The bright blue Indian Ocean heaves, with massive, white-capped waves smashing against the Cliffs producing an amazingly weather beaten landscape.
Steep Point is apart of the Zuytdorp Cliffs which are comprised of Tamala Limestone, they formed 5-10,000 years ago when the Earth crust shifted along a fault line during an earthquake which shifted the rock up to 200meters high. Chemical and mechanical weathering continue to shape the landscape.
Todays Earth Science focuses on a little arch that we noticed here at Steep Point.
What is an Arch? A natural arch, natural bridge or, less commonly, a rock arch is a natural rock formation where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion from the sea, rivers or weathering.
Most natural arches are formed from narrow fins and sea stacks composed of sandstone or limestone with steep, often vertical, cliff faces. The formations become narrower due to erosion over geologic time scales. The softer rock stratum erodes away creating rock shelters, or alcoves, on opposite sides of the formation beneath the relatively harder stratum, or caprock, above it. The alcoves erode further into the formation eventually meeting underneath the harder caprock layer, thus creating an arch. The erosional processes exploit weaknesses in the softer rock layers making cracks larger and removing material more quickly than the caprock; however, the caprock itself continues to erode after an arch has formed, which will ultimately lead to collapse.
The choice between bridge and arch is somewhat arbitrary. The Natural Arch and Bridge Society identify a bridge as a subtype of arch that is primarily water-formed. By contrast, the Dictionary of Geological Terms defines a natural bridge as a "natural arch that spans a valley of erosion."
On coasts two different types of arches can form depending on the geology. On discordant coastlines, rock types run at 90° to the coast. Wave refraction concentrates the wave energy on the headland, and an arch forms when caves break through the headland. Two examples of this type of arch are London Arch—previously known as London Bridge—in Victoria, Australia, and Neil Island in Andaman, India. When these arches eventually collapse, they form stacks and stumps. On concordant coastlines rock types run parallel to the coastline, with weak rock such as shale protected by stronger rock such as limestone. The wave action along concordant coastlines breaks through the strong rock and then erodes the weak rock very quickly. Good examples of this type of arch are the Durdle Door and Stair Hole near Lulworth Cove on Dorset's Jurassic Coast in south England. When Stair Hole eventually collapses it will form a cove.
To log this Earth Cache we require you to visit GZ and WP2 to make some observations, consider the information given, then message us with the following answers to the best of your ability;
1. Starting at the posted coordinates can you see any small or large holes, what has caused these?
2. Move over to WP2, you may need to move closer to see it better depending on your height and the weather conditions, what height do you estimate the arch to be and how wide is it? Do you think it's getting wider faster than it's getting higher? What factors influenced your answer?
3. Which type of costal arch is this?
4. A photo of your team or GPS at Steep Point, please none of the Arch, upload as many photos as you like! (Optional)
You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 1 week. Cachers who do not fulfil the Earth Cache requirement will have their logs deleted without notice.
Source: Wikipedia, Department of Parks and Wildlife
