April 5, 1815
On Mount Tambora in the eastern part of Indonesia
The earth’s biggest eruption within historic times hit Indonesia in
1815. This eruption had a VEI of 7 and it not only devastated
Indonesia but also changed climates all over the world for years
The area we now know as Indonesia experienced earth’s two most
powerful volcanic eruptions. The first, Toba, the biggest within the
last two million years, had a VEI of 8 and was located in western
Sumatra. It erupted 74,000 years ago. The second was Tambora,
which had a VEI of 7 and was located east of Java. Tambora erupted
in April of 1815 and was the biggest in all of recorded human history.
It is likely that the tsunami of 2004, also in Indonesia, will go
down in history as the most destructive tsunami ever experienced.
Thus, Indonesia has come to be known as the locale of the world’s
most deadly earthquakes and eruptions. When Tambora erupted,
two million tons of debris rose upwards to a height of twenty-eight
miles. The heavier parts fell back to earth but the lighter particles
stayed aloft, circling the earth and blocking out much of the sunlight.
Temperatures dropped in every country of the world and
many people subsequently referred to the year 1816 as the one
without a summer.
Some sense of the immensity of this event can be gleaned from the dimensions
of the mountain before and after the eruption. It was approximately
thirteen thousand feet high before and nine thousand afterward and this
loss of four thousand feet of height occurred in a mountain that was thirtyeight
miles wide at its base. The total weight of the material that rose
into the atmosphere was ten times greater than that of Krakatau in 1883
and one hundred times more than the amount ejected from Mount St.
Helens in 1980. The sound of the explosion was heard in Western Sumatra,
a thousand miles away. The heavier fragments of lava fell back into
the ocean and the combination of heat and impact with the water created
mini eruptions from which the finer quantities of dust were added to the
already darkened atmosphere. The actual volume of ash produced by these
secondary was ten times greater than the amount generated by the original
eruption. For years, the average amount of sunshine reaching the earth
was reduced. More than ninety thousand were killed by the eruption, most
of them indirectly through the starvation and disease that followed as everything
around them was obliterated. The mountain itself continued to
burn for three months before finally coming to rest.
The local devastation in places within a hundred miles of the eruption
is well illustrated in the experiences of the villagers of Bima, a small community
at the eastern end of Sumbawa, the island on which Tambora previously
stood. For several days following the eruption they were shaken
day and night by the ongoing explosions that followed the main eruption.
A dense ash cloud in the atmosphere above Bima completely shut out the
sun for four days, similar to Vesuvius when the people there also experienced
total darkness at midday. The weight of fallen ash was too much
for most of the homes and they collapsed. At the same time, throughout
the early hours following the eruption, tsunamis flooded the village just
as they had done elsewhere on the Island of Sumbawa. Later, government
officials found innumerable numbers of corpses of people and animals on
the ground around Bima or floating nearby on the sea. In different places
around the world the impact of Tambora was not as dramatic as it was in
Bima but nonetheless enormously destructive.
Reports from northern Europe described the harvests for the year that
followed as being so poor that starvation was common among poorer families.
The industrial revolution was still young and most people were still
totally dependent on what they could wrest from the soil. Many were
reduced to eating rats. Grain prices rose four-fold in that part of the world
and, when other countries tried to be capitalize on the shortage, the price
of grain on the international market rose extremely high. France suffered
more than other countries of Western Europe because it had been involved
in Napoleonic wars right up to the year 1815 and the whole social life of
the country had been severely strained from the stresses of warfare. In the
year 1816, farmers were afraid to take their produce to market because of
the dangers of being robbed by hungry people along the way. Government
troops had to be called in frequently to protect these farmers. In the
United States, farmers in New England had so many crop failures over
such large areas that many of them migrated westward to Ohio and elsewhere.
All over Indonesia, in addition to the immediate destructive effects of
the eruption, masses of ash, rock particles, and sulfur dioxide gas were
deposited everywhere and they continued to give trouble year after year
for some time. Sulfur dioxide is a poisonous gas used in the manufacture
of sulfuric acid, a highly toxic substance. An invisible gas, the presence of
sulfuric acid in the air created complications for the digestive system of
both humans and animals and many died as a result. Lack of rain was
another consequence of the disaster. Since all vegetation was destroyed,
transpiration activity stopped. Normally new soil forms quickly in tropical
areas that experience volcanic eruptions and the eruptions contribute
to much of the tropical rainfall that comes frequently in latitudes such as
those in Indonesia. Accordingly, population there is always dense and
crops can be grown two or three times a year in such soil. However, it
took several years before Indonesia was able to grow crops of the kind and
quality needed to feed its huge population.
The collection of thousands of islands that we now call the nation of
Indonesia always had a fascination for the people of Europe, largely the
result of the value of spices in centuries past. Marco Polo was the first to
acquaint the West with what was then called the Spice Islands. That was
about eight hundred years ago but it was considerably later when the importance
of spices appeared. By the middle of the nineteenth century and
after considerable success in both farming and stock rearing, Europeans
were faced with the problem of preserving meat in winter. Animals were
slaughtered in the fall to reduce the cost of feeding them and the meat
was then salted away in iceboxes to preserve it for six or more months.
The taste of salted meat after all that time was, to say the least, not very
attractive and Europeans discovered that one specific item from the Spice
Islands, pepper, was the thing that would profoundly enhance its flavor.
Trade in pepper between Indonesia and Europe became a top priority. So
great was the value of this commodity that a single peppercorn was considered
to be worth its weight in gold and this became evident in the rules
governing stevedores at European ports. Whenever they had to handle peppercorn
shipments from Indonesia their pockets were sewn up to minimize
theft.
The island chain that is Indonesia extends in a curved form for more
than 4,000 miles. Closely following the islands on their south side but
deep below sea level stands the tectonic boundary between the Indo-
Australian Tectonic Plate and the Eurasian one. The Indo-Australian Plate
is moving northeastward beneath and at a slightly faster rate than the
movement of the larger Eurasian Plate and this subduction is the main
cause of the numerous volcanic eruptions and earthquakes we hear about
from Indonesia. Within the overall picture of these two huge tectonic
plates, there are smaller components of each that can at times be extraordinarily
destructive. The gigantic earthquake of 2004 off the coast of Sumatra
was caused by the Indian portion of the Indo-Australian Plate subducting
under the Burma portion of the Eurasian Plate and creating one of
the most powerful earthquakes of all time. The tsunami that accompanied
this event and radiated outward from the entire 750 miles of plate that
had been displaced is also likely to go down in history as the most destructive.
It was literally an earth-shattering wave and it took several minutes
for the displacement to be completed.
The island on which Tambora stood is more than two hundred miles
north of the tectonic boundary. The magma that rises from below this
boundary has to travel upward about one hundred miles from that boundary
and from far below it to reach the summit of Tambora and cause the
eruption. It is the work of geologists to trace as completely as they can
both the source of the magma and its age. Only by doing this can information
be found on the past history of volcanic activity as big as Tambora’s
and thereby be able to predict when another one might occur. The sea
floor is the top of the outermost solid layer of the earth’s surface, known
as the crust, often several miles thick. Below the crust is where the
magma exists and there have weaknesses or fault lines in that crust if
the magma is going to rise to the surface. One such fault line stretches
northwestward for 150 miles from the Island of Sumba across the tectonic
boundary to the Island of Sumbawa, the site of Tambora.
It was through breaks in this fault line that magma built up over the
centuries. Geologists did not know very much about either tectonic plates
or subduction at the time of Tambora’s eruption and it was about 150
years later that the secrets of earth’s mosaic of tectonic plates became
known. Ever since that time geologists have been busy making use of this
new knowledge to trace the history of earthquakes and volcanic eruptions.
The age of the oldest lava on the site of Tambora is about 50,000 years
and the youngest are the layers of ash and rock that were deposited on
Indonesia in 1815. Beneath these deposits are some older rocks, about
5,000 years old. This discovery, while inconclusive, gave geologists at
least one clue to the likelihood of another Tambora-type eruption arriving
soon. If the time difference between the 1815 event and the one that came
before it is 5,000 years, then one possibility is that there will not be another
one before another 5,000 years.
More work needs to be done by geologists on the history of eruptions
in this part of Indonesia in order to obtain the average time between these
destructive events over the millions of years through which they have
occurred. Only when armed with data of that kind can we estimate the
future with some degree of accuracy. The final phase of the 1815 event
seems to have begun three years earlier. Reports from local observers tell
of noisy steam eruptions, sometimes followed by dark clouds of volcanic
ash, happening from time to time between 1812 and 1815. These things
were the result of hot magma encountering moisture as it rose within the
mountain. Overall, in the course of the three years, there was a two-inch
layer of ash on the sides of the volcano and on the ground.
References for Further Study
de Boer, Jelle Zeilinga, and Sanders, Donald T. 2002. Volcanoes in Human
History: The Far-Reaching Effects of Major Eruptions. Princeton, NJ:
Princeton University Press.
Decker, R., and Decker, B. 1989. Volcanoes. New York: W. H. Freeman.
Harrington, C. R. 1992. The Year Without a Summer? World Climate in 1816.
Ottawa: Canadian Museum of Nature.
Simkin, T, and Siebert, L. 1994. Volcanoes of the World. Tucson, AZ: Geoscience
Press.
Stommel, Henry M., and Stommel, Elizabeth. 1983. Volcano Weather: The
Story of 1816, The Year Without a Summer. Newport, RI: Seven Seas
Press.
Sumber:
Angus M. Gunn., Encyclopedia of disasters : environmental catastrophes and human
tragedies, GREENWOOD PRESS, Westport, Connecticut, London, hal. 98 – 102.
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