Cannonball Concretions EarthCache

“Artillery Rocks”

B first became aware of this fabulous location on a photography tour a few years ago and has been wanting to place an EC here for some time to bring it to the attention of others (beyond the local fisherman who know it rather well...)

Geological Features of Artillery Rocks

Artillery Rocks is a wonderful example of two geological phenomenon: Honeycomb weathering, and Cannonball Concretions. Today's lesson will focus on the latter.

Safety Precautions

This area of the coast can bring dangerous exposure to the elements, in the form of both tides and swell. Please check the conditions before descending from the carpark as high tides and large swells can made this area extremely dangerous. If the conditions are not friendly, please stay safe and come back at another time. Please also be aware that to get from the carpark to GZ you will need to descend a stone staircase and traverse the coastal rock. It is not a strenuous exercise but may present a challenge for cachers with certain physical restrictions. The terrain rating of this cache has been set accordingly. Sturdy footwear is strongly recommended.

Cannonball Concretions

A 'cannonball concretion' present as a spherical piece of rock. Occasionally, an object such as a fossil, shell or similar object may be surrounded by groundwater rich in calcite. This leads to the calcite filling the gaps in the sandstone, working outwards from the object leading to formation of a concentric and hardened section of the original sandstone. Over time, the softer, surrounding sandstone erodes aware leaving only the spherical, mineralised concretion behind. The concretion, which started out as sandstone will now have a makeup of approximately 50% calcite. Ironically, given we are used to geological phenomena evolving over significant time periods, the formation of cannonball concretions can be quite rapid. In Lincolnshire in the UK concretions have been discovered to have formed around military shrapnel deposited in the area during both World War I and II.

Logging Requirements

In order to claim a find on this cache you will need to do two things: Read the cache page, and visit the two cannonball concretions at the posted coordinates (shown in the pic above). This will allow you to complete the logging requirements. Answers to questions should be forwarded through message center or email to BFMCgeocachers@gmail.com. Please do not include answers to any question in your log however the required photograph must be attached to your log. Feel free to log your find immediately but please send answers through within a reasonable timeframe (which I would class as 3-5 days). Logs without sending answers or without the required photograph may be deleted. Given the large volume of tourists through this area if you are visiting from overseas and will be sending through answers upon your return home please note this in your log so I know to allow you extra time.

1. Question 1: Given what you have learned, approximately how many % of the concretions in front if you is calcite?
2. Question 2: These concretions have formed in sandstone. Compare the 2 concretions at GZ to the sandstone supporting them. Does the concretion maintain the same appearance as the original sandstone, or is it altered. If it is altered, in what way is it visually different?
3. Question 3: Do you think these concretions will remain where they are, or will something happen to set them free? Explain your reasoning behind your choice. There is evidence to support what will happen in the immediate area around GZ if you have a look around.
4. Photo requirement: You must attach a picture to your found it log that contains the two cannonball concretions at GZ as well as either your caching name or yourself. You can write in on a piece of paper, a namebadge (I often use my lanyards from previous mega events to good effect in these situations) or any other means available to you but it must be an original part of the photograph (not added after the fact) and be clearly visible (so small items may not be suitable). Keep in mind I mentioned above that I found this location on a photography expedition, I can spot a photoshop job at 20 paces without too much difficulty!