After seeing the article in the Nanaimo News Bulletin by Chris Bush about the "cannonballs" in Nanaimo sandstone cliffs we thought they would be a great topic for an Earthcache. We visited one of the sites and did some research and wanted to share this extraordinary place. The location is in Blue Heron Community Park in Ladysmith and is open dawn to dusk. Please be gentle with the site, take only pictures, and leave only footprints.
This earthcache may not be accessible at very high tides so please check before trying to visit. https://www.tides.gc.ca/en/stations/7917
A concretion is a hard, compact mass formed by the precipitation of minerals cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin concretio "(act of) compacting, condensing, congealing, uniting", itself from con meaning 'together' and crescere meaning "to grow". They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. They typically form when a mineral precipitates and cements sediment around a nucleus, which is often organic, such as a leaf, tooth, or piece of shell. Concretions are found in a variety of rocks but are particularly common in shales, siltstones, and sandstones.
Spherical rock formations are sometimes referred to as cannonballs and are commonly found where wave and weather erosion has worn away the softer debris and sandstone revealing the formations. Notice on this beach they are similarly shaped but each is distinctive with cracks and scars from glacial processes and weathering. They also vary in size, from quite large to quite a bit smaller. They’re one of the oldest geological features people come across in the region. Shoreline concretions in the Yellow Point area formed in the sandstone from 85 to 65 million years ago, according to Jerome-Etienne Lesemann, professor at Vancouver Island University’s Earth science department.
To log this earthcache, read the description and visit the site then send the answers to the owner. Please do not include them in your log.
1. What size are the concretions and how many do you see?
2. Describe the shape and colour of the concretions.
3. What type of rock are these concretions formed in?
Please post pictures of yourself at GZ or of anything of interest. Please DO NOT post the answers to these questions in your log. You also do not need to wait for a response before logging your find.
https://www.nanaimobulletin.com/news/natures-cannonballs-protrude-from-nanaimos-sandstone-cliffs-and-beaches/?utm_source=second-street&utm_medium=email&utm_campaign=NBU+-+Morning+Alert&emailmd5=BB64C8AB5981BC90DADEE2CDDE00111F&emailsha1=22976153102224452491604811512512037176577511819252&emailsha256=34fc2a7b4c65c2f62ea267c61c76f250c68308ad1f1a4ba418009cb4cbd49113
https://en.wikipedia.org/wiki/Concretion#:~:text=In%20concentric%20growth%2C%20the%20concretion,concretions%20that%20grow%20with%20time.