El Chichón, also known as Chichonal, is an active volcano in
Francisco León, north-western Chiapas, Mexico. El Chichón is part of a geologic zone known as the Chiapanecan Volcanic Arc. El Chichón is a complex of domes with a tuff ring, made of ejected volcanic material, located between the
Trans-Mexican Volcanic Belt
The Trans-Mexican Volcanic Belt ( es, Eje Volcánico Transversal), also known as the Transvolcanic Belt and locally as the (''Snowy Mountain Range''), is an active volcanic belt that covers central-southern Mexico. Several of its highest peaks h ...
and the
Central America Volcanic Arc
The Central American Volcanic Arc (often abbreviated to CAVA) is a chain of volcanoes which extends parallel to the Pacific coastline of the Central American Isthmus, from Mexico to Panama. This volcanic arc, which has a length of 1,100 kilometer ...
.
[Robock, Alan, 2001: Volcanic eruption, El Chichón. in ''Encyclopedia of Global Environmental Change'', vol. 1, Ted Munn, Ed., (John Wiley and Sons, London), 736.] El Chichón erupted in 1982; prior to this, activity had not occurred since 1360, although debates in literature occur around an eruption occurring in 1850.
El Chichón became famous for its 1982 eruption. In little under a week, the presumed dormant volcano produced three
plinian eruptions (March 29, April 3, and April 4).
The eruptions released a substantial amount of sulfur dioxide and particulates into the atmosphere. While the total volume of the eruption was much smaller than the famous eruption of
Pinatubo in 1991, El Chichón's impacts were equally significant on global climate.
[Robock, A. (2000). Volcanic eruptions and climate. Reviews of Geophysics, 38(2), 191-219] El Chichón is often overlooked in comparison to other historic eruptions, yet the 1982 eruptions provide important lessons on preparation for volcanic disasters and the influence volcanoes can have on climate.
1982 eruption
The 1982 eruption of El Chichón is the largest disaster in modern Mexican history.
The powerful 1982 explosive eruptions of high-sulfur, anhydrite-bearing magma destroyed the summit lava dome and were accompanied by
pyroclastic flows
A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
and surges that devastated an area extending about 8 km around the volcano.
[Francis, P., and Oppenheimer, C., 2004, Volcanoes, Oxford University Press, 521pp] A total of 9 villages were completely destroyed, killing 1,900 people.
A new 1-km-wide, 300-m-deep crater that now contains an acidic
crater lake
Crater Lake ( Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fill ...
was created.
The landscape was covered in ash up to 40 cm in depth.
Over 24,000 km
2 of countryside was affected,
devastating coffee, cocoa, banana crops, and cattle ranches. The eruption caused natural dams to form along the Rio Magdalena river, inducing
lahars
A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley.
Lahars are extremel ...
, which destroyed key infrastructure. The total damage caused by the 1982 eruption is believed to amount to $55 million
(equivalent to $132 million in present-day US dollars).
Lack of preparation
With more than 600 years since the last major eruption of El Chichón, few people were aware of the volcanic risk. Most presumed it to be a
dormant volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
or extinct. Throughout 1980 and 1981 earthquakes were felt in the surrounding regions, and geologists
hazard mapped the region highlighting risks, no increases were seen in monitoring activity.
Climate impacts
It was a
VEI-5 eruption, injecting 7 million metric tonnes of
sulfur dioxide and 20 million metric tonnes total of particulate material into the
stratosphere,
[Robock, Alan, 1984: Climate model simulations of the effects of the El Chichón eruption. ''Geofísica Internacional'', 23, 403-414.] which circulated the Earth in three weeks.
[Robock, Alan and Michael Matson, 1983: Circumglobal transport of the El Chichón volcanic dust cloud. ''Science'', 221, 195-197.] The amount of sulfur dioxide is comparable to the 20 million tonnes of the 1991 eruption of
Mount Pinatubo
Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive histor ...
.
The eruption occurred just as the
1982–83 El Niño event
The 1982–1983 El Niño event was one of the strongest El Niño events since records were kept.
It led to droughts in Indonesia and Australia, widespread flooding across the southern United States, lack of snow in the northern United States ...
was initiating; because of this several scientists suggested that the El Chichón eruption caused the El Niño.
However, climate modeling and detailed studies of past eruptions and El Niño have shown that there are no plausible theories connecting these two events, and that the timing was merely a coincidence.
As a result of the simultaneous eruption and El Niño, the climate felt the impacts of both, making it challenging to separate their effects on temperature.
Generally a volcanic event would induce global cooling, particularly in summer months, however no cooling was seen in the first year after the El Chichón eruption, because the El Niño produced large compensating warming.
The climatic effects also triggered winter warming patterns observed within northern hemisphere continents in 1982 and 1983, with temperatures increasing over North America, Europe, and Siberia. During the same winter, Alaska, Greenland, the Middle East, and China witnessed colder temperatures than normal, highlighting regional variation.
The variation is said to be a result of
volcanic aerosols impact on the atmospheric wind patterns, including the Arctic Oscillation.
Ash properties
The deposition of ash in the surroundings of the volcano varies with distance from the volcano since the ash particles vary in size. This is problematic, since ash samples are collected from the ground in order for the optical and chemical properties to be measured which too will vary with distance from the volcano. Therefore, one can only measure certain relevant parameters for samples collected from the air or from the ground. However, some samples are of greater interest than others. Thus, the most important samples are the ones furthest from the volcano (80 km,
100 km,
) due to the fact that they are the most likely to reach the
stratosphere. In particular, the 80 km one has shown similarities with stratospheric ash samples.
Chemical properties
For ash samples around 100 km away from the volcano, the presence of the soluble and non soluble components has been identified.
The water-soluble components present in the highest concentration are
Ca2+ and
. There have also been traces of
Na+,
K+,
Mg2+,
and
Cl−.
The non-soluble part consists mostly of
SiO2 (around 59%) and
Al2O3 (around 18%) along with trace amounts (less than 5%) of other components, such as
CaO,
Na2O and
Fe2O3.
Optical properties
For the El Chichón cloud, the
optical depth
In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to ''transmitted'' radiant power through a material.
Thus, the larger the optical depth, the smaller the amount of transmitted radiant power throu ...
has been measured to be around 0.3 around mid-visible wavelengths.
The
imaginary part of the refractive index, describing the attenuation of radiation for the 80 km sample, varies between 0.004 at 300 nm and 0.001 at 700 nm. Based on these results, the real part of the refractive index of the stratospheric El Chichón ash is estimated around 1.52, while the imaginary part is expected to be slightly less than the one measured for the ground samples.
See also
*
List of volcanoes in Mexico
References
*
Further reading
*
External links
*
Photo of El Chichón in March 1981, prior to eruption
{{DEFAULTSORT:El Chichon
Volcanoes of Chiapas
Volcanic crater lakes
VEI-5 volcanoes
20th-century volcanic events
Landforms of Chiapas