Research - Basic Cave Chemistry
STEP 1
In the first step, rain water falls through the atmosphere where it combines with carbon dioxide. Carbon dioxide is a gas but it dissolves into the rain water, making it slightly acidic. Most people are familiar with soda water. This is just water with lots of carbon dioxide dissolved into it. The most important thing to note is that this step produces a hydrogen ion.
In the first step, rain water falls through the atmosphere where it combines with carbon dioxide. Carbon dioxide is a gas but it dissolves into the rain water, making it slightly acidic. Most people are familiar with soda water. This is just water with lots of carbon dioxide dissolved into it. The most important thing to note is that this step produces a hydrogen ion.
STEP 2
In the next step the hydrogen ion comes in contact with calcium carbonate, which is the prime constituent of limestone. When it does, it liberates a calcium ion and another hydrogen carbonate ion. It is this process that starts to dissolve the rock away. Although there are other minerals in limestone, when the calcium carbonate dissolves away the other minerals are loosened within the rock matrix and so they start to crumble away too.
In the next step the hydrogen ion comes in contact with calcium carbonate, which is the prime constituent of limestone. When it does, it liberates a calcium ion and another hydrogen carbonate ion. It is this process that starts to dissolve the rock away. Although there are other minerals in limestone, when the calcium carbonate dissolves away the other minerals are loosened within the rock matrix and so they start to crumble away too.
STEP 3
In the final step, two hydrogen carbonate ions come back in contact with a calcium ion to reform calcium carbonate. Water and carbon dioxide is liberated in this process. When the calcium carbonate forms it is as a crystal and this is what constitutes the familiar cave formations. The process can be accelerated by removing water from the reaction or the carbon dioxide. For instance, if the atmosphere is very dry, such as near the surface, water loss will be significant, driving the reaction forward. If carbon dioxide levels build up in a cave, such as from lots of people exhaling, then it can actually drive the reaction in reverse, causing calcium carbonate to be dissolved.
In the final step, two hydrogen carbonate ions come back in contact with a calcium ion to reform calcium carbonate. Water and carbon dioxide is liberated in this process. When the calcium carbonate forms it is as a crystal and this is what constitutes the familiar cave formations. The process can be accelerated by removing water from the reaction or the carbon dioxide. For instance, if the atmosphere is very dry, such as near the surface, water loss will be significant, driving the reaction forward. If carbon dioxide levels build up in a cave, such as from lots of people exhaling, then it can actually drive the reaction in reverse, causing calcium carbonate to be dissolved.