Re: Volcano lake turns from blue to red


"Aidan Karley" <doIlookDAFTenoughTOpost@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
skrev i en meddelelse
news:VA.00000ed4.13371c22@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
http://news.yahoo.com/s/ap/20060529/ap_on_re_au_an/vanuatu_volcano_1

WELLINGTON, New Zealand - A lake atop a rumbling volcano on the South
Pacific island of Ambae has changed color from blue to bright red,
puzzling scientists.

Mount Manaro, one of four active volcanos on the island nation of
Vanuatu, has been showing signs of erupting for only the second time
in 122 years.

"We are still ... trying to understand this change of color in the
lake from blue to red," Geology and Mines Department director Esline
Garae said by telephone Monday from Vanuatu's capital, Port Vila.

She said two scientists on Ambae Island were monitoring Lake Vui as
well as seismic activity on the 5,000-foot Mount Manaro.

If the change of color "comes from new activity in the ground or just
chemical change in the lake - these are two things I want to know from
those guys before I can say anything" about the danger posed by the
volcano, she said.

Mount Manaro last erupted in November 2005, forcing half the island's
10,000 inhabitants to evacuate their villages. An 1884 eruption killed
scores of villagers.

New Zealand volcanologist Brad Scott said Lake Vui's color was "quite
a spectacular red," but what had caused it "is the $64,000-question."

He said water samples from the lake would help determine what was
happening in the crater and below it.

The color change could be a chemical process or gas from molten
volcanic rock or something else coming into the lake, he said.

Three other volcanos in Vanuatu - Lopevi, Yasur and a two-crater volcano
on Ambryn Island called Marum and Benbow - have spewed rocks, ash, smoke
and steam in recent weeks.

Vanuatu, formerly the New Hebrides Islands, is made up of 13 main
islands located about 1,400 miles east of Australia.

Hmm, from the symptoms, my first guess would be to look at the iron
content of the water, and particularly of the sediment settling from a
random
water sample. It would be nice to compare with analysis results from
*before*
the change, but in the real world there won't be appropriate data.

Odd. Are they trying to boost a story out of nothing? I mean .. Clear water
may be nice and blue, ironstained water somewhat turbidite. It seems too
obvious to be what's behind the headline.

Carsten

Sources? Well the #1 contender would be a hydrothermal water stream
having started coming into the lake from somewhere below. Which would
suggest
the possibility, at least, of there being colour gradients visible on
satellite
and/or aerial photography that could indicate localisation of the input,
flow
rates and concentrations, *without* putting people at prolonged risk.

--
Aidan Karley, FGS
Aberdeen, Scotland
Written at Mon, 29 May 2006 08:51 +0100, but posted later.



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