Limestone and Karst Landscape
Any landscape which characteristics derive primarily from the dissolution of limestone rock is termed a karst landscape. Limestone is a type of sedimentary rock that is formed in the ocean by chemical processes that result in the precipitation of calcium carbonate. Over thousands to millions of years, the calcium carbonate can accumulate to form layers of limestone rock hundreds of meters thick. The shells of many animals, that live in the sea, consist of calcium carbonate (calcite and aragonite). When the animals die, their shells are left as fossils on the ocean floor where they may accumulate into thick deposits. Once this rock is uplifted above sea level by geologic forces, ground water percolates through it and slowly dissolves it, creating a variety of solution features, e.g. tower karst. This feature is dominating the landscape of peninsular Thailand.
The dissolution of the limestone often creates sinkholes and caves. Thick, resistant limestone is also necessary for tower karst to develop and caves are also common in tower karst regions; however, the towers that characterize tower karst can only develop in the tropics because it is only there that the right conditions of rock and climate interact to create these magnificent features.
Consistent with the fact that tower karst can only develop in the humid tropics, it has been determined that tower karst development requires a minimum of 1,2 m of precipitation per year and an average temperature of 18° C. Peninsular Thailand, with a minimum rainfall of 1,3 m per year and an average annual temperature of about 27° C clearly meets these climate requirements. Consequently, the tower karst in this area is well-developed and sometimes spectacular.
Types of Limestone
• Coquina: Limestone that contains large pieces of shells or coral
• Chalk: Limestone that is formed from microscopic marine organisms
• Travertine: Limestone formed around a spring or a waterfall
• Oolite: Limestone that is formed around high-temperature areas such as tropical seas or lagoons
Pure limestone is snow white. Other colors are caused by other rocks:
• Limonite and siderite cause yellow-brown shades
• Hematite causes red
• Glauconite and chlorite cause green
• Bitumen causes gray to black
Questions:
• From here can you witness any formation of karst towers?
• Which kind of limestone is this? Please explain your choice.
• Limestone on Koh Sichang is marine in origin. Please examine the stones and describe which evidence of that you can find.
