Introduction
Flash to Iceland, 1783. Dotted with
vast basaltic lava fields, glaciers, and a
varied ecosystem, the island now serves as a
great tourist attraction. The basaltic lava
fields come from the many volcanoes
throughout Iceland, fueled by a hotspot,
similar to that of Hawaii’s hotspot. Of
course, being such a volcanically active
island, there’s bound to be one or two large
volcanic eruptions. One such large eruption
had begun on the 8th of June, 1783, when a
several-kilometer wide fissure suddenly
opened up near the volcano of Grimsvotn,
located in the southeastern portion of
Iceland. Lava effusion rates were some of
the most rapid of the entire millennium, and
eventually 580 km2 of land were covered by
basalt from the eruption. The most
devastating aspect of the eruption was not
the lava itself, however, but the gasses that
were emitted as a result.
Approximately “122 Mt. i.e.
122,000,000 tonnes of sulfur dioxide”
(Hellman 19) were released over the few
months that the eruption took place. Much
of this sulfur dioxide reached the upper
troposphere, a section of the atmosphere that
extends to around 10 kilometers above sea
level in Iceland. Penetrating the
stratosphere, much of this SO2 was blown by
winds to cover a large portion of continental
Europe. The consequences were felt at large.
Iceland itself lost 10,000 people due to this
poisonous gas (11), and Europe was left
under a sulphuric haze. This haze would kill
thousands of more people across Europe,
and even go on to affect North America and
portions of Asia.
Volcanic Gasses
Volcanic gasses are gasses released
during volcanic eruptions; these gasses
include CO2 (carbon dioxide), SO2 (sulfur
dioxide), and H2O (water). The most
devastating of these gasses are CO2 and SO2.
Carbon dioxide is a compound that humans
breathe out; although it is a greenhouse gas
expelled by volcanic eruptions, the CO2
content is not great enough in most
eruptions to cause any significant amount of
global warming, as the expulsion of CO2
from volcanic eruptions is merely a part of a
natural carbon cycle.
SO2 is much more notable, in that
many volcanic eruptions are capable of
ejecting large quantities of this gas,
depending on the geographic location of the
volcano. Volcanoes like El Chichon in
Southeastern Mexico are capable of
releasing large quantities of SO2 as a result
of the volcano being adjacent to the
Chicxulub impact crater, where large
amounts of sulfur were deposited on impact
(Albert). SO2 can spread globally if enough
is ejected via volcanic eruptions or winds
permit the spread of SO2 across the planet. It
is worth mentioning that SO2 can dissolve
into water in the stratosphere to form
sulfuric acid; sulfuric acid can reflect
sunlight (ca.gov), and volcanic eruptions
that eject significant quantities of SO2 (on
the order of tens of millions of tons) have
been noted to drastically reduce global
temperatures.
SO2 is an incredibly toxic gas, and if
inhaled, it can cause “burning of the nose
and throat, breathing difficulties, and severe
airway obstructions” (ATSDR); if significant
quantities of SO2 are inhaled, the situation
can become life-threatening. However, one
doesn’t need to get a large immediate dosage
of SO2 to see the health effects. Many
miners are subject to a constant dosage of
SO2 during work, and this can cause damage
to their lungs over time. This is especially
true with those who have asthma, as their
lungs are more sensitive to damage by SO2
(ATSDR). Sulfur dioxide can also poison
water if dispelled in an environment rich
with water; SO2 dissolves in water to form
sulfuric acid, which can contaminate
ground-water. If water is not filtered
properly, this contamination can negatively
affect human health.
CO2 is also a dangerous gas,
especially in high concentrations. Its most
devastating hazard as a volcanic gas comes
in the form of limnic eruptions. These
eruptions involve lakes, and occur when
large quantities of CO2 are suddenly released
in an explosion (SATREPS). The CO2 stays
relatively close to the ground, and it can
cause asphyxiation/suffocation by pushing
away O2 molecules, leaving less air to
breathe. Although these eruptions are rare,
they can be devastating when near populated
areas. Historical limnic eruptions have been
known to kill thousands, and if proper
preventative measures are not taken,
thousands more can be put at risk of a limnic
eruption.
Current Hazards
Volcanic-induced gasses still pose a
threat today, although the threat is not
exactly with SO2. Large volume effusive
volcanic eruptions (eruptions that erupt lava
in fountains and lava flows) such that which
occurred in Iceland in 1783, are unlikely to
happen in our lifetimes. It is possible that
one may occur, but no signs now point to a
significant effusive eruption occurring
anytime soon.
Limnic eruptions, on the other hand,
pose a much more significant threat; due to a
lack of proper monitoring and little
mitigation efforts, the chance of a limnic
eruption occurring in close proximity with
large population centers is prominent. Lake
Kivu, a lake capable of producing a limnic
eruption, is close to the densely populated
area in Africa, “nestled between the
Democratic Republic of the Congo and
Rwanda” (Jones). A limnic eruption from
Lake Kivu, which can produce millions of
tons of CO2, would be devastating to the
surrounding area. And, due to the densely
populated region surrounding the lake, death
tolls can number in the hundreds of
thousands.
Of course, a limnic eruption at Lake
Kivu is not guaranteed and can be
successfully mitigated using human-made
degassing mechanisms (Jones). This can
allow for CO2 beneath the lake to be
released in a peaceful manner, preventing a
sudden outburst of CO2. In that sense, efforts
must be taken to prevent large-scale limnic
eruptions from occurring near areas with
large populations, and areas at risk of large
limnic eruptions must be more actively
monitored to assure that these lakes are
degassing properly.
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