石化湖

真實的冥河！坦尚尼亞「石化湖」

如果地球上真有冥河(Styx)存在，一定就是位於坦尚尼亞的「納特龍湖」。這片看似靜止不動的水域隱藏一個致命秘密，它可以使任何碰觸到湖水的動物化為石頭，因此被科學家稱為「石化湖」。

「石化湖」水溫高達攝氏60度，且因溶入附近大裂谷的火山灰，水裡全是一種名為「泡鹼」的天然化合物；這種化合物由碳酸鈉和微量小蘇打組成，使水的酸鹼值落在pH9至pH10.5之間，逼近強鹼標準。

即使在極端嚴苛環境中仍能生存的鹼性羅非魚，也很難在「石化湖」裡存活。對於其他動物來說更為致命，牠們一旦浸泡到水裡，沒過多久便會死亡，並且鈣化成一具具栩栩如生的石雕。

http://www.newscientist.com/article/mg21929360.100-deadly-lake-turns-animals-into-statues.html#.UkzPbBBmM1L

Deadly lake turns animals into statues

• 01 October 2013 by Rowan Hooper
• Magazine issue 2936. Subscribe and save
• For similar stories, visit the Picture of the day Topic Guide

(Images: Nick Brandt)

ACCORDING to Dante, the Styx is not just a river but a vast, deathly swamp filling the entire fifth circle of hell. Perhaps the staff of New Scientist will see it when our time comes but, until then, Lake Natron in northern Tanzania does a pretty good job of illustrating Dante's vision.

Unless you are an alkaline tilapia (Alcolapia alcalica) – an extremophile fish adapted to the harsh conditions – it is not the best place to live. Temperatures in the lake can reach 60 °C, and its alkalinity is between pH 9 and pH 10.5.

The lake takes its name from natron, a naturally occurring compound made mainly of sodium carbonate, with a bit of baking soda (sodium bicarbonate) thrown in. Here, this has come from volcanic ash, accumulated from the Great Rift valley. Animals that become immersed in the water die and are calcified.

Photographer Nick Brandt, who has a long association with east Africa – he directed the video for Michael Jackson's Earth Song there in 1995 – took a detour from his usual work when he discovered perfectly preserved birds and bats on the shoreline. "I could not help but photograph them," he says. "No one knows for certain exactly how they die, but it appears that the extreme reflective nature of the lake's surface confuses them, and like birds crashing into plate glass windows, they crash into the lake."

When salt islands form in the lake, lesser flamingos take the opportunity to nest – but it is a risky business, as this calcified bird (top) illustrates. The animals are all arranged in poses by the photographer. Above, on the right we have a sea eagle and on the left a dove, in what is surely the most horrific depiction of the "bird of peace" since Picasso's Guernica.

Brandt's new collection of photos featuring animals in east Africa, Across the Ravaged Land, is published by Abrams Books.

This article appeared in print under the headline "The lake that petrifies"