Fig.1: Kawah Putih Lake
Kawah Putih, which means "White Crater" in Indonesian, is a volcanic crater lake located in West Java. The lake is known for its striking turqoise color and the surrounding white landscape, which is caused by the high sulfur content of the area. Kawah Putih Lake is one of the two craters that make up Mount Patuha. The local climate is often quite chilly; the temperatures are frequently around 10o Celsius. This makes a brisk change from the humidity of the north Java plain and the capital city of Jakarta. Kawah Putih is a sizeable highly acid lake (pH 0,5 - 1,3) that changes colour from bluish to whitish green, or brown, depending on the concentration of sulfur and the temperature or the oxidation state. The sand and rocks surrounding the lake have been also leached into whitish colours through interaction with the acidic lake waters (with possible mineral precipitation as well).
While the area is now a popular torist attraction, it has a history of sulfur mining. It was primarily carried out by local miners who worked under difficult and hazardous conditions. These miners extracted sulfur manually using basic tools and transported it on their backs or using makeshift carriers. The work was physically demanding and dangerous due to the toxic fumes and the unstable terrain.
In the early 1900s the crater was Indonesia's most productive volcano-hosted sulfur mine (total production 133000ton). A sulfur plant known as the Zwavel Ontgining Kawah Putih was first established near the lake during the period of Dutch rule in Java. The plant was later taken over during World War II by the Japanese Military. Sulfur, being an essential material for various industrial and military purposes, including the production of gunpowder and other explosives, would have been a valuable resource.
The practice of sulfur mining in Kawah Putih has significantly decreased in recent years as tourism has become the main focus of the area. However, it is the local miners and their arduous labor that have played a significant role in the history of Kawah Putih's sulfur extraction. Entry points of various tunnels which represent the remnants of these mining activities can be seen at several points around the current site.
Fig.2: Former tunnel entrance to a sulfur mine
Sulfur is an essential element for all life, almost always in the form of organosulfur compounds or metal sulfides. Amino acids and two vitamins (biotin and thiamine) are organosulfur compounds crucial for life. Sulfur is one of the core chemical elements needed for biochemical functioning and is an elemental macronutrient for all living organisms.
Fig. 3: Sulfur deposits on a stone
Here's a bit more detail on the different colors of sulfur and the conditions under which they appear:
1. Yellow: The most common color of sulfur, seen in its orthorhombic crystalline form and as a fine powder. This bright yellow is characteristic of elemental sulfur.
2. White: When sulfur vapor condenses rapidly, it can form a fine white powder known as "flowers of sulfur". Additionally, sulfur dioxide (SO2), a gas formed from burning sulfur, can also appear white when condensed into a solid form.
3. Red: Sulfur appears red when it is in a molten state. This color can also be seen in certain allotropes and when molton sulfur cools and transitions through different states.
4. Brown: Amorphous or "plastic" sulfur, formed by rapidly cooling molton sulfur, can appear brown or dark red. This form is less crystalline and has a rubbery texture.
5. Black: Sulfur can appear black in certain chemical compounds, such as when it is combined with other elements or when it is burned, producing a black residue of sulfur compounds like sulfur dioxide and sulfur trioxide.
These colors demonstrate sulfur's versatility and the variety of forms it can take depending on temperature, pressure, and its physical or chemical state.
Crater lakes of active volcanoes represent one of the most extreme natural chemical environments at the Earth's surface. Kawah Putih's lake levels and element concentrations show strong seasonal fluctuations, indicative of a short water residence time in the lake as well. Very low pH values and high concentrations of sulfate, chloride and rock-forming cations are typical of crater-lake water. The lake water is considered highly toxic because the concentrations of Al, As, B, Cl, Cr, Fe, Pb, Mn, Se and SO4 approach or exceed WHO guidelines for portable water. The composition of these fluids is generally considered to be controlled by magmatic degassing and subaqueous influx of such volatiles, although various stages of interaction between a magma-hydrothermal system, meteoric waters and gases can occur. Fluctuations in lake composition may reflect changes in the subaqueous fumaroles, and thus provide insight into the level of volcanic activity.
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Stage 1:
Task 1: According to the listing, sulfur can appear in different colors. Below the green area in Fig. 1 you find rock with some deposits. Which (several?) colors can you find ? Draw conclusions about the concentration of the deposits.
Stage 2:
Task 2: Are there signs of volcanic activity (such as gas bubbles) in the lake ? Look at the vergetation around the lake. Why is it in this condition ?
Task 3: Can you see sulfur deposits on the shore ? Where do this come from ? And finally: What's the smell like ?
Sources:
Fig. 1 - 3: Own
Wikipedia
Geochemistry of the acid Kawah Putih lake, Patuha Volcano. West Java, Indonesia; Journal of Volcanology and Geothermal Research, Volume 97, April 2000, Pages 77 - 104