Parking is free at GZ but is often full, plenty more free parking in the Five Foot Way Car Park, waypoint provided
A stalactite is a of formation that hangs from the ceiling of caves, hot springs, or manmade structures such as bridges and mines. Stalactites may be composed of lava, minerals, mud, peat, pitch, sand, sinter and amberat (crystallized urine of pack rats).
Limestone Stalactites
Limestone caves, where most stalactites are found, are mainly composed of calcium carbonate. When rainwater falls over a cave and trickles through rocks, it carries some of the dissolved calcite contained in the calcium carbonate, through the cracks of the roof of the cave. Once water comes into contact with the air inside the cave, the calcite starts to form around the crack. As water continues to drip, the length and thickness of the calcite grows, and eventually a stalactite forms on the ceiling. It can take a very long time for most stalactites to form - they usually grow anywhere between a quarter-inch and an inch every century.
Lava Stalactites
Lava stalactites form while lava is still active. Lava stalactites formation happens very quickly in only a matter of hours, days, or weeks. A key difference with lava stalactites is that once the lava has ceased flowing, so too will the stalactites cease to grow. This means that if the stalactite were to be broken it would never grow back.
Concrete Stalactites
Stalactites can also form on concrete and on plumbing where there is a slow leak. The way stalactites form on concrete is due to different chemistry than those that form naturally in limestone caves and is due of the presence of calcium oxide in cement. Concrete is made from aggregate, sand and cement. When water is added to the mix, the calcium oxide in the cement reacts with water to form calcium hydroxide which is carried by rainwater through cracks in the cement. Stalactites can form when the solution emerges on the underside of the concrete structure. A straw shaped stalactite which has formed under a concrete structure can grow as much as 2 mm per day in length.
To log this Earthcache
Send the answers to the following questions to me through my profile BEFORE you log the cache. If you feel you have the answers correct please go ahead and log it, I will contact you if there is a problem.
1. At GZ look up at the walls of the old fort, it was completed in 1743, if you found stalactites here how long do you think they would be?
2. At the waypoint you will see an entrance to a small tunnel, it’s half way up the steps and on the other side of the railings. Look into the tunnel from the grassy bank, do you see stalactites ? I hope you can, are they the same length as your answer to Q1?
3. From what you see and the length of them do you think these stalactites are limestone, lava or cement ones?
4. How much do you think they will grow, if at all, over the next 100 years?
Photos are welcome, but no spoilers please.