GC6GN6M Broughton Island (Earthcache) in New South Wales, Australia created by Elev8!on [mrnoo17]

GC6GN6M ▼

A cache by Elev8!on [mrnoo17] Message this owner

Hidden : 4/29/2016

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Size: Size: other (other)

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Geocache Description:

*This is not a cache to be taken lightly. It can be potentially hazardous if the correct precautions are not taken. ENSURE TO CHECK WEATHER AND SWELL UPDATES BEFORE ATTEMPTING THIS JOURNEY! An expedition to the island should not be done without adequate preparation. In saying this, completing this journey is an extraordinary experience not to be missed.*

Broughton Island is a truly magical place. It is one of the nesting grounds of the migratory Mutton bird (a noisy, inquisitive bunch!), the most northern landing ground of the Fairy penguin, and home to countless species of marine life. Apart from being a deck-chair enthusiasts paradise, it also has a vast range of some unusual rocks to get any geologists senses tingling! I am no geology expert, but I certainly learned a lot from my trip here!

Completing the Earthcache Requirements:

This can be done realistically in a big summers day, however, if you choose, camping for small groups is permitted (for a small fee) at Refuge Cove. If you are fortunate enough to sail around in a yacht, the north side of the island has a surprisingly deep, sheltered beach. For more info about camping on the island, look at: http://www.nationalparks.nsw.gov.au/camping-and-accommodation/campgrounds/Broughton-Island-campground

Completing the cache will involve exploring the coastline and inland features of the island. The easiest way to do this is in a kayak or a tinnie on a calm day. The order of the waypoints is only a guide, they can be done in any order that is easiest. I am no expert in geology, so feel free to correct/discuss with me if I have made any mistakes. I have done some reasonably extensive travelling and have never seen so much geological diversity in such a small area!

1. North East Corner
Much of the rock on this North eastern peninsular is quite sharp to walk on. This is because it is made of trillions of little stones and shells. Strictly speaking, this is not really a limestone as it is more than just coral and shells. It is in fact a conglomerate as it has shells as well as pebble make up the large slab of rock on this peninsular. What is the average size of the individual shells and pebbles at the coordinates?

Between waypoint 1 and 2, there is some fantastic scenery! When going around the island clockwise, you will see the spectacular cliffs and coastline of the island.

Further around the corner, the channel, the geology changes again. The cliffs at the end of the channel are actually some form of sedimentary rock, from a distance it looks like shale. This rock is layed down in thin layers to form a tall, but very brittle. 2. Looking Glass Isle
A large rocky isle to the south of the the main island. On a closer investigation, you will find that it isn't really just one island! A channel has been cut through the island by the continual pounding of waves. Considering the hard, metamorphic nature of the rock, this erosional process happens over thousands of years. To the north of this split, is an eyelet shape hole formed by a similar process. Estimate the height and width of the "Looking Glass"

3. South Rocky Beach

Looking Glass Isle, as seen from the beach, is only a short distance away. However, the rock changes yet again. On this beach is a plenitude of some very quirky rocks:

As you will discover, every rock on this beach is different to the next. Stranger still, rocky fingers seen in the image with Looking Glass Isle, are different again. They are a much plainer colour. They also alternate between sedimentary and metamorphic. The sedimentary rock in this case is similar to the Hawkesbury (Sydney) Sandstone, with a relatively small particle size. The Metamorphic rock, formed from intense heat and pressure, is Granite. It forms from the slow crystallization of magma below Earth’s surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, grey or white colour with dark mineral grains visible throughout the rock. However, due to prolonged exposure to the elements, lichen has grown and weathering has discoloured the surface. Take a walk along the beach and Count the number of fingers and identify how many are metamorphic, and how man are sedimentary. Do you notice any pattern?

4. Western Caves

Unless you have a kayak, or willing to swim to shore from a larger vessel, this may be quite tricky as there is no land access to this beach. However, there is another sea cave on the adjacent, easily accessible beach (access coords under "beach rope access"). On this beach is the "Alternate cave" which can be used as a substitute. Caves such as these are formed by continual weathering by the pounding waves; well, the front, western entrance is! The side, beach opening is a little different! Suggest how the side entrance was formed. (Hint: maybe when the beach structure was a little different to today?) Also, take a step (or two) into the cave. Take a look at the roof, of the cave, apart from the sedimentary rock, is there any other sort of rock in the roof? If so, what is it? (Hint, you have already seen it in a previous waypoint)If you really are not able to reach this cave, Simply answer:What is the height and length of this cave?

Also, this beach has some distinctly coloured cliffs. Like Mount Bulladelah, it is an extremely rare deposit of Alumite. The Quarry Mt Bulladelah, according to one source, is the only place in the Southern Hemisphere where this deposit was able to be extracted above ground.
. What colour is this rock? Would you describe it as strong or weak? Why?

5. Little Poverty and Esmerelda Beaches
Return back to the starting coordinates. From here, a well maintained trail will take you through to this:

This beautiful spot is the "Central Hub" of the island, with camping, toilets and "town" at Esmerelda beach. If you are planning on staying the night on land, you will stay on one of the platforms erected in the bird colony. Using your observations, Do you notice any difference between Providence Beach and Little Poverty/Esmerelda Beaches? Can you suggest why?

6. Mt Broughton

The highest peak on the island, a mere 70 meters! However, when you stand at the top, it really feels like several hundred meters in elevation. Views of surrounding mountains on the mainland are extensive, with Mt Tomaree and Yaccaba in the south and North/middle/south brother in the north.

Getting up the hill may prove to be a little tricky. The easiest way is to follow the rocks from Providence Beach, around to the "REF2" coordinates. From here, some fairly overgrown paths will lead to the peak.Describe the rock up here, grain size, colour, particle colour? Locate the plaque on the mountain. What type of rock (specifically) is it attached to? (Careful! A bit of a trick question!)

Further Notes:

With these questions completed, please send me an email with your answers. I am just a geology enthusiast, and certainly not a geologist, so if you find a mistake that I have made, please let me know so I can fix it! Similarly, I do not expect for every answer to be completely correct either. The main thing that I am looking for is a serious attempt where I can correct if necessary, and feel free to correct me!

Kayak is most definately the preferred craft. The necessary water travel in one is about 15-20km. I took the best part of a day to do this at a pretty relaxed pace. Make sure to pack provisions for unforeseen weather/swell conditions, and check weather/tides/swell before leaving!

Parking for this is a little tricky.
Kayakers: If you have a 4x4 or even a Forrester or RAV4 (preferably one of the old generations with more ground clearance), a relatively easy 4x4 carpark is located at "P1". If you have not driven on sand before, probably a good idea to try somewhere a little closer to civilisation first. 15psi and byo air compressor. For those with 2wd Dark point "P2" is next best. A good idea to have some wheels for the kayak as it is a decent trek to the beach from here.
Poweboat/Sailboat: Launch from Hawkes nest is closest to the island.

Although the guidelines do not require photos to be part of a log, I'm sure that you will be completely ecstatic about your trip to the island, and will want to share your experience with a decent size log and maybe some "visual aids"to accompany (entirely optional of course!) As this isn't quite a park and grab, feel free to email me in regards to any helpful tips/useful information to help plan the trip!

Happy Caching!!!

Additional Hints (Decrypt)

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Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)

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Broughton Island EarthCache

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