What are the reasons for the change of the colors of the three lakes of
the volcano Kelimutu on Flores (Indonesia)?
Peter Lorenz
Hi Mr. Lorenz,
I'm only going to be able to give you a general answer because I don't
know the details. The coloration comes from suspended particles of
sediment in the lakes. That only generates the question of why there are
different colors of sediment in the lakes. The sediment color depends on
the minerals that make it up, and most of the minerals in a volcanic
setting such as this are going to be secondary alterations of the original
lava and ash. The nature of these secondary minerals is very sensitive to
all kinds of chemical conditions including the acidity of the area, the
temperature, the amount of sulfur getting into the system, and lots of
other things. It takes only a small change in one or more of these for
one alteration mineral to be produced rather than another.
An example I can think of would be that perhaps one lake has a few more
streams draining into it so that it gets slightly more diluted by rain
water. This will make the chemistry different and will probably also
lower the temperature. One lake might have many more hot sub-surface
fumaroles, causing a higher input of acid gases as well as a higher
temperature. You can hypothetically change all the variables in order to
get the particular set of water chemistry and sediment chemistry you want.
I know this hasn't been a specific answer. For more details you might try
looking through a recent article by Gregory Pasternack and Johan Varekamp
in volume 28 of "Geochemical Journal" (pages 243-262).
Sincerely,
Scott Rowland, University of Hawaii
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