Karakteristik kimiawi air danau kawah Gunung Api Kelud, Jawa Timur pasca letusan tahun 1990
Authors: EKA KADARSETIA, SOFYAN PRIMULYANA, PRETINA SITINJAK, and UGAN BOYSON SAING
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Kelud is a strato type volcano characterized by phreatomagmatic and magmatic eruptions. Since
last eruption in 1990, the volcano has showed no-more signifi cant volcanism. Currently, there is an
opened westward crater lake as a remained eruption crater containing meteoric water and volcanic
gases condensate generated from subsurface.
Analysis result of lake water exhibits that its chemical composition was fl uctuated due to an
infl uence of factors such as seasons, rates of volcanism activity and reactivity of internal chemical
elements within the lake water.
The volume of lake water increases during the wet season and experiences dilution to make
declination of chemical components within the water. Temperature of the lake water increases as
well as volcanic intensity, simultaneously to make addition of dissolved chemical compounds and
elements such as SO4, Cl, B, and F and creates acidic water. Fumarole/solfatara released anykind
of gases, such as H2O, CO2, CO, HCl, SO2, H2S, HF, H2, HBr, NH3, CH4, H3BO3, and N2. Moreover
interaction of andesitic rock and acidic water apparently produces ionic source of Na, K, Ca. Mg,
Fe, Al including trace elements such as Zn, Li, Sr, As, Rb, Cr, Pb, Ti, Ni, Cu, Ce, and Be.
The composition of crater lake water of the Kelud volcano is included into an immature water category with HCO3. The fl uctuation of element, compound and gas contents within the lake water with
their depletion trend during the period of 1990 – 2005 may be related to decreasing of volcanism activity
in the duration of 1990 post-eruption.
Keywords: Kelud, chemical composition gas, crater lake water, volcanic activity, post 1990 eruption