Limestone: what is limestone? Limestone is a sedimentary rock widely distributed in New Zealand. The rock is made up of more than 50% calcium carbonate (CaCO3), derived from the shells of tiny marine fossils. Limestone commonly forms in shallow marine waters from an accumulation of fossils of marine organisms. In the Waikato there are two main quarries where limestone is formed, one at Te Kuiti and another at Otorohanga, close to where the Waitomo Caves are located. In this report I will investigate and analyze the chemical processes involved in the formation of limestone caves and the consequences these chemical processes have on the environment. Limestone formation: In New Zealand most limestones are made up of shell fragments and limestone muds that were originally deposited in shallow marine waters. These fragments are loose sediments, which undergo diagenesis to form a hard limestone sedimentary rock. The loose sediment is buried underground, which puts a lot of pressure on the calcium carbonate sediment. This application of pressure is called pressure dissolution. Through this pressure the calcium carbonate actually begins to dissolve. It then seeps into the pores and re-precipitates as cement, which provides the solid characteristic of limestone. Formation of Limestone Caves: Limestone forms when carbonic acid reacts with limestone bedrock. However, we must first see how this carbonic acid was formed: Co2 + H2O H2CO3. The word for this equation is carbon dioxide + water carbonic acid. This reaction occurs when evaporated water combines with carbon dioxide in the atmosphere to produce carbonic acid. Include soil Co2. The carbonic acid escapes... into the middle of the paper... into the cave atmosphere. The air we breathe contains carbon dioxide, so Waitomo Cave's decision to limit the number of daily visitors to some caves is a great way to reduce the impact on the balance. (http://books.google.co.nz/books?id=IBESYmQcb0sC&pg=PA119&lpg=PA119&dq=chemical+equilibrium+in+caves&source=bl&ots=XQ9_hSQ5GP&sig=0i8oZ2Z IAyqHOSKd9R2wr3yo7_I&hl=en&sa=X&ei=gLB4U53tMbKp7 AbSwIGQBA&ved=0CCcQ6AEwAA#v=onepage&q= chemical%20equilibrium%20in%20caves&f=false)Another The impact on caves is the extensive roadworks and agriculture that produce an urban lifestyle. Water plays an important role in the process of formation of caves and mineral crystallites. Due to toxic chemicals produced by urbanization, this water is contaminated and poses a threat to the continuity of the caves. (http://www2.nature.nps.gov/views/KCs/CaveKarst/HTML/ET_Threats.htm)