Watch the Lake Nyos Demonstration 
Volcanism, steam explosions, dissolved
gases, gas densities. . . Take your pick. The
story of a unique environmental disaster at
Lake Nyos can motivate your students to learn
about any of these. "A Volcanic
Lake"
Located in the west African
nation of Cameroon, Nyos is one of several
volcanic lakes, formed centuries ago as
rising plumes of magma encountered
groundwater. Heat from the plumes triggered
steam explosions, forming craters that would
become the lakes. Since their violent birth, the
lakes have been tranquil, keeping secret the
strange volcanic danger hidden in their
depths. Legends tell of past disasters, and in
1984 a neighboring lake killed 37 people. . .
But these pale in comparison to what
happened at Lake Nyos in 1986. The
Tragedy
On the evening of August
21st, the quiet waters of Nyos awakened
violently, as a lethal cloud of carbon dioxide
gas erupted from its depths, killing over 1,700
people in a valley below. Most experts believe
that tremendous amounts of the gas,
dissolved in the cold, deep waters of the lake,
were released as this water was brought to
the surface. As the water rose, decreasing
pressure caused bubbles to form just as they
do when a bottle of cola is opened. The
eruption spewed a column of water and gas
over 80 meters into the air, expelling so much
gas that the level of water in the lake was
lowered by over a meter. Because carbon
dioxide is more dense than air, the invisible
gas descended into the populated valley,
causing the deaths. Teaching
Tool
Although it happened in 1986, the tale of this disaster is strange
enough to capture the attention of even your
sleepiest students. . . Then, as they try to
make sense of this horrible night, you will find
their intrigue especially helpful in teaching
them about two important concepts. For one,
Nyos provides a memorable introduction to
the concept that water contains dissolved
gases, and will help them understand the
influence of pressure and temperature. This
provides the basis for understanding such
phenomena as the bends, carbonation, radon
in groundwater, and dissolved oxygen content
(an important consideration in water quality).
Secondly, the downward flow of carbon
dioxide from the lake will bring the realization
that gases vary in density just as aluminum
and lead do. This explains why ammonia and
helium float in air, whereas carbon dioxide
and propane sink. Still another use of the
Nyos situation, would be to have students
propose ways that future eruptions could be
prevented as the storage of gas refills the
deep waters of the lake. National
Geographic
To gain a general
understanding of the disaster, read the article
featured in the September 1987 National
Geographic Magazine . . . "Silent Death at
Cameroon's Killer Lake', by Curt Stager. The
magazine, which devotes over ten pages to
the event, includes several photos,
illustrations, and maps. Stager also
examines the link between the gases and the
lake's volcanic past, and presents ideas
about what may have triggered the upwelling.
Several other magazines have also featured
articles. Lake Nyos Lab
Activity
For those seeking a hands
on approach, WARD'S offers a lab-kit, called
"What Happened at Lake Nyos?".
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