Stalactites in Tunnel of Ketchikan
Photo: Tunnel of Kechikan
This Earth cache will show you stalactites located within the Tunnel of Ketchikan that was finished in 1954.
Here in this tunnel at GZ you can observe various geological processes that are common in older concrete structures, in humid environments.
One of these processes is the formation of stalactites and the presence of iron oxide from rusting reinforcements in older cement structures.
Together, let's take a closer look at how to identify traces of iron oxide inside or outside stalactites, as well as where stalactites grow in tunnels and bunkers.
A stalactite is a formation that grows or has grown downward from the ceiling, in contrast to a stalagmite, which grows upward from the floor.
It is important to note that stalactites are fragile and vulnerable, and they can withstand very little. Therefore, care should be taken and only use the eyes to observe the stalactites and avoid touching them with your fingers.
There are differences in the formation of calthimite and speleothem, which are two types of stalactites.
Calthinite forms on concrete and is the result of chemical reactions different from the chemical reactions that form speleothems.
There are several chemical formulas and reactions that can lead to the formation of stalactites and this varies depending on the degradation processes that occur on old or new concrete structures. There are no uniform decomposition processes.
On the other hand, speleothemes, which are also stalactites, are formed in caverns. They are formed mainly from calcium carbonate (CaCO3) found in rocks such as limestone or dolomite. The calcium carbonate is more soluble in water with higher carbon dioxide (CO2) and lower temperature.
When the rainwater reacts with CO2 in the soil, weakly acidic water is formed via the reaction: H2O + CO2 → H2CO3. This acidic water penetrates the bedrock and dissolves the calcium carbonate via the reaction: CaCO3 + H2CO3 → Ca2+ + 2 HCO3-.
When this solution reaches a cave, the precipitation of CaCO3 occurs due to lower CO2 levels in the cave via the reaction: Ca2+ + 2 HCO3- → CaCO3 + H2O + CO2.
Over time, these precipitates accumulate and form stalactites such as stalactites, stalagmites, and floating stones, which are the most common forms of speleothems.
Calthemite, or stalactite that grows on man-made structures, grows significantly faster than speleothems.
This is because concrete contains more calcium oxide, which is an important component for stalactite formation.
Under favorable conditions, calthmite can grow at the rate of about 2 mm per day.
Calthermite (Soda sraw) is mainly white, but can acquire colors such as black, red, brown, orange, or yellow due to the presence of iron oxide.
When it comes to identifying traces of iron oxide inside or outside stalactites, color changes can be looked for.
The iron oxide gives the stalactite a characteristic rusty color, which is usually red, brown or orange.
These colors may be clearly visible either as stains or as a coating on the surface of the stalactite. It is important to note that not all stalactites will have traces of iron oxide, and there may be variations depending on geological conditions and the presence of metal components in the structures.
As for the places where stalactites grows, they will usually be found in areas with high humidity and sufficient water supply. This includes areas near entrances or openings where moisture can penetrate, as well as places where there are leaks or drips from the ceiling or walls.
Stalactites can also be found in areas where there are natural sources of water, such as if there is an underground river or water flow nearby. When exploring tunnels, bunkers or caves and looking for stalactites, it is important to respect and preserve the natural formation.
Stalactites take a long time to form, and it is part of the unique environment that exists where they form. Avoid touching the stalactite or disturbing it in any other way. Feel free to use a flashlight to illuminate areas where stalactites may be visible, and enjoy the natural beauty and geology found in the tunnel.
Also, stay safe when walking in the tunnel, Only use the sidewalk when you observe.
- Based on your observations, wich type of stalactites is growing here?
- Based on your observations, how long is the longest stalactite you can find?
- Based on the fact that this tunnelwas finnish in 1954, what is the max growth rate in mm/yr for the observed stalactites?
- How does the answer in Q2 compare to the growth rate of a typical concret based stalactite?
- Is there any miscoloring in the stalacites?
- Include a photo in the log without spoiler effects.
Sources: wikipedia.no, no.wikipedia.org, snl.no, ngu.no and maintech.no.
Photo: Stalactites Shasta Caverns