This Earthcache is accessible via boat, paddleboard, kayak, or canoe. While the area is beautiful it can be quite dangerous. Always pay attention to wind and weather patterns before heading out and make sure you have all of the appropriate safety equipment with you at all times. Recommended launch for your watercraft is from Charles Daley Park, however limited parking can also be found on South Service Road. You do not need to exit your watercraft to answer the questions. You do need to physically visit GZ to log your visit. Approaching from Fourth Ave MAY be possible, but would be extremely steep, with limited parking, and an unknown water depth under the bridge. This method of approaching GZ is not recommended.
Today, the GPA43 group was out paddling and we came across a rather interesting phenomenon - something we affectionately referred to as rusticles! However, are they actually "rusticles" or is this just a fun word that I made up? This Earthcache will explain the different between Rusticles and Calthemites, and allow you to make observations at GZ to determine what these growths actually are.
PLEASE do not actually touch the growths! Let's preserve them so future geocachers can explore them as well.
What is a Rusticle?
A rusticle is a formation of rust similar to an icicle or stalactite in appearance that occurs in WET environments (such as underwater) when wrought iron oxidizes. They may be familiar from underwater photographs of shipwrecks, such as the RMS Titanic and the German battleship Bismarck. Rusticles are created by microbial organisms that consume iron.
The word rusticle is a portmanteau of the words rust and icicle and was coined by Robert Ballard, who first observed them on the wreck of the Titanic in 1986. Rusticles can form on any steel object and have been seen on other subsea structures such as mooring chains and subsea equipment. They form more rapidly in warmer climates and can form in water with little to no dissolved oxygen.
The rusticle consists of up to 35% iron compounds including iron oxides, iron carbonates and iron hydroxides. Rusticles are found in a tube shapes of iron oxides which are vertical to one another. Rusticles are found to grow at approximately 1 cm (0.39 in) a year and are most often found in areas of sunken hulls underwater.
Rusticles have been found to most often be composed of iron, calcium, chloride, magnesium, silica, sodium and sulphate while there are other chemical compositions of rusticles but in much smaller quantities.
Structurally, rusticles contain channels to allow water to flow through, and they seem to be built up in a ring structure similar to the growth rings of a tree. The outer surface of a rusticle is smooth red in appearance from the iron(III) oxide, while the core is bright orange due to the presence of crystals of goethite. There are several morphologies of the rusticle, some of which are conical, cylindrical and rusticles on the seafloor.
What is a Calthemite?
Calthemite is a secondary deposit, derived from concrete, lime, mortar or other calcareous material outside the cave environment. Calthemites grow on or under, man-made structures and mimic the shapes and forms of cave speleothems, such as stalactites, stalagmites, flowstone etc.
Calthemite stalactites can form on concrete structures and "artificial caves" lined with concrete (e.g. mines and tunnels) significantly faster than those in limestone, marble or dolomite caves. This is because the majority of calthemites are created by chemical reactions which are different to normal "speleothem" chemistry.
Calthemites are usually the result of hyperalkaline solution (pH 9–14) seeping through a calcareous man-made structure until it comes into contact with the atmosphere on the underside of the structure, where carbon dioxide (CO2) from the surrounding air facilitates the reactions to deposit calcium carbonate as a secondary deposit.
Calthemite flowstone coloured orange by Iron Oxide (from rusting steel reinforcing) deposited along with calcium carbonate (CaCO3).
Calthemites are generally composed of calcium carbonate (CaCO3) which is predominantly coloured white, but may be coloured red, orange or yellow due to iron oxide (from rusting reinforcing) being transported by the leachate and deposited along with the CaCO3. Copper oxide from copper pipes may cause calthemites to be coloured green or blue. Calthemites may also contain minerals such as gypsum.
Tasks and Required Info
After enjoying a lovely paddle from the recommended put-in Coordinates, you should now be paddling under a large concrete tunnel. This is where you will make your observations from. You do NOT need to exit your vessel to gather the answers.
1. Read the above description and state, in your own words, the difference between rusticles and calthemites.
2. Looking inside the tunnel, you will see several sections of growth. Choose one and describe it - is it wet? dry? smooth? shiny? bumpy? slimy? what colour is it? is it made up of many sections, or one large growth?
3. Are they well developed, or just starting to form? What is the approximate size of the largest one you see at GZ?
4. Based on the above description and your observations, what are these (rusticles or calthemites?)
5. Mandatory: Include a photograph of yourself, your GPS, a signature item, thumbs up, etc with your favourite sample. You do not need to show your face in the photo, but your photo must be unique to you.
Please send me the answers using the Geocaching Message Center or send me an email with your answers to the above questions, then go ahead and log this earthcache. You do not need to wait for my response to log. I will contact you if there are any issues with your answers. Feel free to post additional pictures as well, but please do not post your answers with your log.
This EarthCache has been prepared by a proud:
