In the Oku volcanic plain, 200 miles northwest of Yaounde, Cameroon, lies a body of water known to local villagers as “the Bad Lake.”
Lake Nyos sits within a silent crater amid miles of mountainous farmland. For centuries, inhabitants of the region knew its waters to run deep and still. But on the night of Aug 21, 1986, its surface suddenly erupted in a 300-foot-tall toxic spray that sent a lethal mist roiling through the countryside.
Overnight, 1,746 people suffocated.
Joseph Nkwain was the first survivor to emerge from Subum, a farming settlement located three miles from Lake Nyos. Of the residents in the village, 400 lived. His daughter was among the 400 who did not. In March of 1987, less than a year after the catastrophe, Joseph recounted his experience to interpreter Dr. E. Shanklin.
On the night of the explosion, while his daughter slept, Joseph sensed a dense heat lingering in the air and believed that the first rains of the wet season were finally upon them.
“I heard some sound… Like an airplane… It was as if I was in a dream… All of a sudden, my skin became very hot and I perceived something making some dry smell. I could not speak… I could not open my mouth. I heard my daughter snoring in a terrible way, very abnormal. So I forced myself to stand up from the bed, I was already weak… When crossing to my daughter’s bed, in the middle of the floor, I collapsed and fell.”
Joseph remained unconscious until the following morning, when he was roused by a neighbor pounding on his door. His body was covered in open wounds that he could not account for.
“I wanted to speak, my breath would not come out… My daughter was already dead… I went to [her] bed, thinking that she was still sleeping. I never knew what was happening until I went outside. Everywhere was quiet, I managed to go over to my neighbors’ houses. They were all dead. I tried [their] doors, they were bolted inside, I shouted through a window, I saw them lying.”
Those who were alive remained in an intoxicated slumber until the following evening. Surmising that the event must have happened all over, Joseph set out on his motorcycle to find his remaining family.
“As I rode from Subum, passing through Nyos, I didn’t see any sign of any living thing.”
This was a nightmare shared by thousands of locals who watched their family members and neighbors die inexplicably. Those who rushed outside to investigate the source of the explosion collapsed within seconds as a chemical cloud stories high swept through the streets. In the surrounding fields, roughly 3,500 livestock died within minutes.
Over the course of the next two days, travelers and aid workers came upon roads littered with the bodies of men, women, and children who had perished in their tracks.
Denizens of the Oku volcanic region attributed the disaster to a vengeful female spirit they have long believed to haunt the lakes and rivers of the region. Scientists sought another explanation.
For many years, the actual cause of the eruption remained a mystery. The volcanic activity that formed the lake’s crater some 400 years ago is no longer active. So how did a still body of water explode without warning?
Researchers found that high levels of CO2 were dissolved in groundwaters as a result of fissures in the lakebed. Most crater lakes degas in natural intervals, restoring their chemical state to some degree of stability. Lake Nyos does not. As a result, its CO2 concentration reached more than five gallons of CO2 dissolved in every gallon of water.
According to the Environmental Protection Agency, the normal CO2 content in fresh air is only .03 percent. When Lake Nyos erupted, it shot roughly 1.2 cubic kilometers of CO2 into the air in 20 seconds, assaulting nearby inhabitants with air saturated at over 17 percent of noxious gases.
Since the 1986 disaster, pipes have been installed within the lake that siphon water from the CO2-rich lower layers up to the surface. By allowing the gas to vent itself at regular intervals, scientists hope to prevent the massive accumulation and inevitable overturn of toxins within the water.
Concern remains, however, about nearby Lake Kivu, a geologically similar crater lake situated in the Virunga volcanic field. With 1,000 times the amount of CO2 in Lake Nyos, and with a history of toxicity that previously caused the extinction of its marine life roughly every thousand years, a volcanic disturbance could result in a devastating event of epic scale.
Scientists continue to closely monitor the lakes in these volcanic regions and are taking measures to prevent similar tragedies in the future.
Feature photo courtesy of Wikimedia Commons.