Biggest
Volcanic Eruption
YELLOWSTONE CALDERA
A
Giant Eruption
Caldera volcanoes are the Extreme
Volcanoes. These are the most powerful and catastrophic types of volcanoes
in a category by themselves because of the unique way in which they
form. This type of volcano is shaped more like an inverse volcano. An
enormous magma chamber bulges up beneath the ground from the extremely
high pressures of the trapped gases within. Ring-shaped cracks form
outward from the magma chamber toward the surface and these act as relief
valves for the magma to escape. Once the accumulated pressure has been
sufficiently released through a serious of extremely powerful pyroclastic
and plinian eruptions, the ground above the magma chamber subsides or
caves in, leaving a large depression. Caldera volcanoes are the largest
on earth, with some calderas measuring from 15 to 100 kilometers wide.
Scientists are just beginning to understand
these types of volcanoes and have only recently identified the characteristics of this type
of eruption. Since this type of eruption has not occurred anytime during
recorded history there have been no human witnesses to record observations
of this type of event. The lack of a real-world example makes it even
more difficult for scientists to study this type of volcano and very
little about them is understood. But from the evidence that scientists
have been able to gather about caldera eruptions in earth's past, all
signs point to events so cataclysmic that they may have changed the
course of the evolution of life on earth. Witness the following eruptions:
Toba Eruption
Approximately 74,000 years ago on the island of Sumatra, Indonesia,
a volcanic eruption so violent occurred that it proved to be apocalyptic
for the human race. Scientists estimate that the eruption may have ejected
up to 6,000 km3 of magma and pulverized rock and sufficient sulfur gases
to form 5,000 megatons of stratospheric sulfuric acid aerosols. The
suspension of so much material in the earth's atmosphere resulted in
a Volcanic Winter that lasted all year long, every year for several
years. The severe drop in global temperatures had catastrophic effects
on vegetation and the food chain dependent upon it for survival - including
humans.
Scientists have examined the genetic
codes of seemingly disparate and distant races of people and found there's
actually very little genetic variability in the entire human race. The
evidence indicates that something happened to the human gene pool approximately
74,000 years ago where only a very few humans remained alive on the
planet (say 5,000 to 10,000), and the current population has grown from
these selectively few genotypes. Our existence in such great
numbers today (over 6 billion strong) is a testament to our tenacious
ability to survive. But could an eruption like that happen again? Some
scientists are studying the evidence and believe that there's a real
possibility it could happen in the Yellowstone Caldera…
The Yellowstone Caldera
Yellowstone National Park in Wyoming, USA is a haven for vacationers
and tourists coming to
appreciate the area's rugged natural beauty. It is also an attraction
because of its mysterious volcanic activity. In the last 50 years scientists
have been closely studying the volcanic activity in the Yellowstone
area to understand the source of this smoldering cauldron and how it
has behaved in the past. By studying the pattern of eruptions in the
past, scientists hope to predict what it will do in the future.
Scientists estimate that approximately
2.1 million years ago the first large caldera-forming eruption occurred
in the Yellowstone area. From the evidence they have gathered it appears
there have been three such cataclysmic eruptions in the Yellowstone
area in the last 2.1 million years, each occurring at intervals of 600,00
to 800,00 years apart. The most recent eruption in the Yellowstone Caldera
occurred 640,000 years ago.
According
to the U.S. Geological Survey…
"The three caldera-forming eruptions, respectively,
were about 2,500, 280, and 1,000 times larger than the May 18, 1980
eruption of Mt. St. Helens in Washington State. Together, the three
catastrophic eruptions expelled enough ash and lava to fill the Grand
Canyon."
The initial eruption of 2.1 million
years ago was 2,500 times more powerful than the Mt. St. Helens eruption
and perhaps was the largest, most violent volcanic eruption in the history
of earth. Enough ash and volcanic debris exploded from the eruptions
to cover the entire western half of the United States with about a four-foot
deep layer of ash. Roughly 600 cubic miles of material were thrown into
the atmosphere. Unlike many of the world's caldera-forming volcanoes
that are found over subducting tectonic
plates, the Yellowstone Caldera is fed by what geologists call a
hotspot beneath the crust. This is the theory that explains
how volcanic activity can occur in the middle of tectonic plates, away
from geologically active plate margins.
An enormous magma chamber 40 by 80
kilometers lies in wait beneath the giant Yellowstone Caldera. Scientists
have recently surveyed the ground in the enormous caldera and have found
the ground seems to be bulging upward, indicating the magma chamber
is on the move. Since there are no historical precedents for this type
of eruption, scientists do not know how to predict if a giant caldera-forming
eruption will occur again. One thing they do know is that the Yellowstone
eruptions were far, far more powerful and violent than the Toba eruption
of 74,000 years ago. If the Toba eruption could reduce the human species
to a few scrappy survivors, can you imagine what another eruption of
the Yellowstone Caldera could do to us?
