A Perfect Murder

Lake Nyos, Cameroon

Fact: Lake Nyos is a crater lake above a magma chamber

Volcanic eruptions release large quantities of poisonous gases such as CO2

Under normal conditions CO2 is released gradually from the magma chamber into the lake

Fact: Lake Nyos lies above a constructive plate boundary

Large events such as earthquakes and landslides can causes gases

to come out of solution

There are 3 lakes in the world saturated with CO2

Fact: underwater volcanoes heat overlying water and disturb sediment

The bottom 80m of water was free of sediment

Lake temperature was found to be unchanged

Fact: the lake was turned red/brown in colour following the disaster

Lake sediment had a high iron content

But - only the top 10m of water was discoloured

Fact: survivors reported feeling warm and smells of rotten eggs

Tests on US fighter pilots have revealed that CO2 at

concentrations of >6% acts as a sensory hallucinogen.

Fact: victims’ bodies were found to be covered in burns

Deep water is very cold.

Dry ice

Fact: people travelling on the back of a pick-up truck survived but the driver died

CO2 is more 1.5 times as dense than air

Fact: dead bodies showed no sign of struggle

Many people and animals appear to have died in their sleep

"I could not speak. I became unconscious. I could not open my mouth because then I smelled something terrible . . . I heard my daughter snoring in a terrible way, very abnormal . . . When crossing to my daughter's bed . . . I collapsed and fell. I was there till nine o'clock in the (Friday) morning . . . until a friend of mine came and knocked at my door . . . I was surprised to see that my trousers were red, had some stains like honey. I saw some . . . starchy mess on my body. My arms had some wounds . . . I didn't really know how I got these wounds . . .I opened the door . . . I wanted to speak, my breath would not come out . . . My daughter was already dead . . . I went into my daughter's bed, thinking that she was still sleeping. I slept till it was 4:30 p.m. in the afternoon . . . on Friday. (Then) I managed to go on my motorcycle . . . As I rode . . . through Nyos I didn't see any sign of any living thing . . . I was unable to walk, even to talk . . . my body was completely weak.“ a survivor’s report

1700 people died4000 livestock diedAll animal life diedIncluding insects

Fact: people living nearby reported hearing a loud explosion

A storm resulted in a long period of heavy rain

and/or

Fact: low level white cloud was observed above the lake and surrounding countryside

The cloud remained very close to ground level and seemed to

‘flow’ like water

Fact: usually CO2 is naturally dissipated into the atmosphere by currents in the water

Crater lakes are often very deep and surrounded by steep sides