charangk said:
Dam the link is blocked at my office
. can anyone post it here.. plz
trangely on August 17, causing a misty cloud to form above the surface of the water. Then without warning, on August 22, the lake suddenly exploded; water and gas shot a couple of hundred feet into the air. The CO2 had taken up so much space in the lake that when it was finally released 1.2 cubic kilometers of CO2—enough to fill 10 football stadiums—in as little as 20 seconds. (Are you old enough to remember the huge volume of ash that Mt. Saint Helens released when it erupted in 1980? That eruption released only 1/3 of one cubic kilometer of ash—a quarter of Lake Nyos’s emission.)
CLOUD OF DOOM
Grazing cattle killed in the 1986 Lake Nyos disaster (Image Credit: Water Encyclopedia)
Cattle herders graze their animals on the hills above Lake Nyos, and after the lake disgorged as much as 80% of its massive store of CO2 in one big burst, dead cattle were found as high as 300 feet above the lake, indicating that the suffocating cloud shot at least that high before settling back onto the surface. Then the gas poured over the crater’s edge into the valley below, traveling at an estimated 45 miles per hour.
For people living in the village closest to the lake, death was almost inevitable. A few people on hillsides had the presence of mind to climb to higher ground; one man who saw his neighbors drop like flies jumped on his motorcycle and managed to keep ahead of the gas as he sped to safety. There were the lucky few. Most people didn’t realize the danger until they were being overcome by the gas. Even if they had, it would have been impossible to outrun such a fast-moving cloud.
CURIOSITY KILLED THE CAT
In villages father away from the lake, people had a better chance of survival, especially if they ignored the noise the lake made as it disgorged its CO2. Some survivors said it sounded like a gunshot or an explosion; others described it as a rumble. But people who stepped outside their homes to see where the noise had come from, or to see what had caused the rotten egg smell (a common smell “hallucination” associated with CO2 poisoning) quickly collapsed and died right on their own doorsteps. The sight of these first victims passing out often brought other members of the household to the door, where they, too, were overcome…and killed.
People who were inside with their windows and doors shut had a better chance of surviving. There were even cases where enough CO2 seeped into homes to smother people who were lying down asleep, but not enough to kill the people who were standing up and had their heads above the gas. Some of these survivors did not even realize anything unusual had happened until they checked on their sleeping loved ones and discovered they were already dead.
AN OUNCE OF PREVENTION
The disaster at Lake Nyos was only the second such incident in the recorded history—the 1984 incident at Lake Monoun was the first. To date, scientists believe that only three lakes in the entire world, Nyos, Monoun, and a third lake called Lake Kivu on the border of Congo and Rwanda, accumulate deadly amounts of dissolved CO2 at great depths.
It had taken about a year to figure out what had happened at Nyos. Then, when it became clear that the lake was filling with CO2 again, the government of Cameroon evacuated all the villages within 18 miles of the lake and razed them to prevent their inhabitants from coming back until the lake could be made safe.
Scientists spent the next decade trying to figure out a way to safely release the gas before disaster struck again. They eventually settled on a plan to sink a 51/2-inch diameter tube down more than 600 feet, to just above the floor of the lake. Then when some of the water from the bottom was up to the top of the tube, it would rise high enough in the tube for the CO2 to come out of solution and form bubbles, which would cause it to shoot out the top of the tube, blasting water and gas more than 150 feet into the sky. Once it got started, the siphon effect would cause the reaction to continue indefinitely, or at least until the CO2 ran out. A prototype was installed and tested in 1995, and after it proved to be safe, a permanent tube was installed in 2001.
RACE AGAINST TIME
As of the fall of 2006 the tube was still in place releasing more than 700 million cubic feet of CO2 into the air each year. That’s a little bit more than enters the lake in the same amount of time. Between 2001 and 2006, the CO2 levels in Lake Nyos dropped 13%.
But the scientists who study the lake are concerned that 13% is still too small an amount. The lake still contains more CO2 than was released in the 1986 disaster, and as if that’s not bad enough, a natural dam on the north side of the lake is eroding and could fail in as little as five years. If the dam collapses, the disaster of 1986 may prove to be just a small taste of things to come: In the event of a dam failure, 50 million cubic meters of water could pour out of the lake, drowning as many as 10,000 as it washed through the valleys below. That’s only the beginning—releasing that much water from the lake would cause the level of the lake to drop as much as 130 feet, removing the water pressure that keeps the CO2 at the bottom of the lake and causing a release of gas even more catastrophic than the devastation of 1986.
SOLUTION
Degassing Lake Nyos (Image Credit: Michel Halbwachs Degassing Nyos)
Scientists and engineers have devised a plan for shoring up the natural dam with concrete, and it’s believed that the installation of as few as for more siphon tubes could reduce the CO2 in the lake to safe levels in as little as four years. The scientists are hard at work trying to find the funding to do it, and there’s no time to waste: “We could have a gas burst tomorrow that is bigger than either (the Lake Monoun or Lake Nyos) disaster,“ says Dr. George Kling, a University of Michigan ecologist who has been studying the lake for 20 years. “Every day we wait is just an accumulation of the probability that something bad is going to happen.
The article above was reprinted with permission from Uncle John’s Bathroom Reader Wonderful World of Odd.
This book focuses on the odd-side of life and features articles like the strangest TV shows never made, the creepiest insect on Earth, odd medical conditions, and many, many more.
Since 1988, the Bathroom Reader Institute had published a series of popular books containing irresistible bits of trivia and obscure yet fascinating facts. Check out their website here: Bathroom Reader Institute
