Aniakchak Caldera., Alaska
The
subject of Volcanoes is so vast that it is hard to know where to start.
I had toyed with the idea of doing a page on volcanoes but not being
an expert I didn't know by which end to start and I didn'r really
want to do "Another" page about Hawaian Volcanoes
or Pinatubo... until one day.
I
was watching the TV one evening and switching channels when I came
across a BBC documentary about Super volcanoes. Having switched over
after the the start I missed the title and the theme of the documentary
and was half watching and half toying with the idea of switching channels
again when I actually started
listening. The narrator was explaining how a palaeontologist, studying
fossils in Antelope county, Nebraska , stumbled across what was probably
one of the most astounding and intriguing sights a palaeontologist
could ever expect to find. It was the sight of a sudden cataclysm.
Hundreds of fossilized prehistoric animals enveloped in volcanic ash¹.This
was intriguing because there are no volcanoes in Nebraska and it is
a known fact that volcano eruptions, such as Mount St Helens (Wa)
considered a strong eruption, only spread ash as far as ± 30
miles from the initial point of eruption.
(¦ In fact this had happened at least twice
before in prehistoric times. Once 11 million years ago when the 'Bruneau-Jarbridge'
eruption occurred and once ±750 000 years ago when the cataclysmic
Long Valley, Ca, volcanic
eruption blew out 150 cubic miles of magma as far east as Nebraska)
( By
now I was beginning to follow the documentary with some interest).
All things considered the scientists
where starting to look further afield and determined that the ash
actually came from a volcanic eruption some 1000 miles to the west!*
(NOAA
map of the USA). If this was indeed the
case the scientists where discovering the existence of a geological
force of such dimensions it would relegate a lot of other geological
or meteorological phenomena to a lesser degree of importance.
The
geologists had backtracked the ash, from Nebraska, to the initial
point of eruption. They had found a depression,
or caldera¹
, in the ground and estimated that the caldera was the result of a
geological implosion, measuring, in the process, the caldera to be
of ± 50 sq miles in size.
¹ Caldera: The Spanish word for cauldron,
a basin-shaped volcanic depression; by definition, at least a mile in diameter.
Such large depressions are typically formed by the subsidence of volcanoes.
Crater Lake ² (Or) occupies
the best-known caldera in the Cascades.
² The Crater
lake Landsat scene in southern Oregon (just below the bottom of the
mosaic) contains several features of special interest both within
and east of the Cascades. The
focal point in the Landsat image is the circular lake known as Crater
Lake. This 12 km wide (8 miles) lake lies within a volcano, known
as Mt. Mazama, that collapsed and erupted violently about 10000 years
ago, probably before humans had settled in the region, expulsing thick
ash beds ( much more than expelled from Mt. St. Helens in 1980).
Klamath Lake lies near the bottom of the image. The blue lake to the
east is Summer Lake. The Great Sandy Desert (dark blue) is a series
of volcanic flows that are roughly coeval with the Snake River Plains
to the east.
Striking also is the conspicuous large elliptical feature northeast
of Crater Lake. It resembles a huge volcanic caldera. The western
part is known as the 'Walker Rim' is a cliff composed of volcanic
flows however solid evidence for a caldera was not obvious. This may
be a coincidental artifact of several topographic features that because
of vegetation distribution gives the impression of ellipticity.
By
sounding the ground under the caldera², as well as in the vicinity,
the geologists found traces of a subterranean chamber. Traces of vertical
shafts in the earth's core were also found and it was deduced that
these shafts had been formed by magma pushing up through faults in
the earths crust allowing the magma to flow into the subterranean
chamber and gradually fill it until it had completely
filled the chamber and could apparently fill the chamber no further.
However the magma had apparently continued to pour into the chamber
causing the ceiling of the chamber to convex upwards. This continued
until the pressure was so great that the roof of the chamber eventually
exploded propulsing lava
and rock over such as distance as to reach Nebraska ± 1000
miles to the east.
² Volcanoes
containing tephra sheets, such as the composite cones, are more prone
to forming calderas once an eruption occurs.
At
this point in the documentary the narration switches back to Yellowstone
explaining how one particular geologist has been monitoring the Yellowstone
Park since the 60s and had noticed variations in the seismological readings.
Tourist attraction that it is and being strategically placed towards the
western rim of the North American
Tectonic plate the Yellowstone National park is closely monitored and
has been since the 1920s, and since that time the geologists have been seeing
that the surface of the Yellowstone National park has been imperceptibly
rising to such a point that by the mid 1980s a rise of 3 foot had been measured.
Yellowstone
and the NASA
Apart
from monitoring the seismological activity in the Yellowstone National
Park, geologists have also been studying the actual layout of the
park itself. This study of the Park took on a new dimension when they
had the chance to collaborate with the NASA. The NASA were wanting
to test a new camera for their next expedition to Mars and the camera
was destined to study the Martian floor and what better way to test
real-time and under relatively similar conditions than to combine
their testings with the geological studies underway in the park. (NB.
Since then the Park is under
Satellite observation).
The scientists had known
about the different geological periods of the Park and where looking
for ways to develope their existing knowledge so when the chance to
work with the NASA presented itself it was seized upon. Before the
testing started the scientists had no idea just how beneficial this
joint venture was going to be and what the long term impact would
be.
The testing started and the NASA's Turboprop flew long and large over the
Park and took a series photographs. Once the photographs were developed
the revelation was immediate. The photographs clearly illustrated not one
caldera but 3 overlapping calderas.
The scientists were astounded. They totally, but naturally,
ignored the existence of any such caldera in the Park. Seen from ground,
with all the trees, mountains, valleys , rivers, etc. it was impossible
to spot any such calderas as they are totally hidden to the eye at ground
level . However once alerted and with the help of the aerial photography
the scientists set about studying the overlapping calderas. They were able
to determine that each of the 3 calderas corresponded with a distinct period
of volcanic activity and they were able to date each activity at intervals
of ± 600 00 years. The 01st and oldest caldera being dated ±2
000 000 years ago (Huckleberry Ridge Tuff ¹),
the 02nd at ±1 300 000 years and the 03rd ±630 000 years ago
(Lava Creek Tuff), sweeping volcanic ash, pumice, and gases across an area
of more than 3,000 sq miles².
(¹ Tuff :
Rock formed of pyroclastic material.)
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This
left the scientists with a dilemma. If the 3 eruptions had occurred
at intervals of ±600 000 years and the last one was ±600
000 years ago then it could be reasonably supposed that another eruption
in the Yellowstone National Park was imminent, if not overdue. The
thought was frightening. Should
a Super Volcano erupt today the result would be a continental catastrophe
with global consequences.
The 'Crater lake' and 'Long valley' supervolcanoes had exploded in
prehistoric times ( ± 11 million years
and 750 000 years ago). . The planet was different then and
above all it was void of human life. When it is considered that ash
from the 'Crater lake' eruption was found ± 1000 miles from
the point of eruption should the Yellowstone park erupt ,
in Wyoming, today lava and rock
would be sent as far as Los Angeles and San Francisco with such devastating
effect that not even the 1906 San Francisco earthquake combined with
the Mt St Helens eruption could compare with the after effects of
a super volcanic eruption.
Super volcano "Yellowstone
Park" today
click to see full size
Aerial view toward
the south of thick intracaldera lava flows of the forested Madison and Pitchstone
Plateaus, burying the west rim of the Yellowstone caldera. The plateaus
preserve the characteristic form of these thick flows, The Teton Range rises
beyond the caldera to the distant skyline.
Although
the planet is covered , from Iceland to New Zealand and all around the Pacific
ring of fire, with innumerable volcanoes that punctuate the planet's
tectonic plates, there are, however, only an estimated 50 "Hotsots"
that could be classified as "Super Volcanoes" and the Yellowstone
National is one of these.
(NB.
The term "Super volcano" is recent and is apparently attributed
to the BBC's Horizon team)
It
is fairly logical to think that a certain number of the other super
volcanos are submarine it may be supposed that there are others, possibly
active on the surface of the earth that are still to be identified,
possibly for the same reason that the 'Crater lake' and 'Yellowstone'
calderas took so long to be identified.
*****************************
Alaskan Earthquakes affect Yellowstone
A
brief excursion to Alaska illustrates
the interactivity of tectonic plates, in this case the North American
plate. According to reports in 2002 a major earthquake in Alaska
set off a chain of smaller earthquakes in the Yellowstone National
Park more than 2,000 miles away. Within hours geysers in the park
changed their eruption patterns, according to the journal "Geology".
Researchers believe that earthquakes keep geysers alive by periodically
shaking loose clogged channels. The Alaskan earthquake was one of
the strongest in North America in the past 150 years.
Thousand smaller quakes
Robert
Smith of the University of Utah says that this study shows that large
earthquakes at large distances can have profound effects on the Yellowstone
geysers and that they did not expect to see these prolonged changes
in the hydrothermal system. The geysers showed changes just a few
hours after the shock waves from the 3 November Alaskan earthquake
passed through triggering more than a thousand minor local earthquakes
with the shock waves, many of them near hot springs and geysers, altering
water and steam pressure in the geysers, opening new channels and
unclogging others.
In
the study, the researchers looked at the eruption patterns of 22 geysers
during the winter of 2002-3 noticing that eight geysers showed major
changes. One of them - Daisy Geyser
- erupted more often but returned to its normal pattern after a few
weeks. The geysers Castle, Plate and Plume also displayed short-term
irregularities that lasted for a few days. Several small hot springs,
not known to have geysered before, suddenly surged into a heavy boil
with eruptions as high as one metre. The temperature at one of these
springs increased from about 42C to 93C in a very short period of
time and became much more acidic than normal. In the same area, another
hot spring, usually cristal clear, turned muddy.
NB. Scientists once believed that an earthquake in one location could
not trigger earthquakes at distant sites. That view was altered after
the 1992 Landers Earthquake (magnitude 7.3) in California's Mojave
Desert triggered a spate of quakes more than 800 miles away at Yellowstone.
Researchers believe that the Alaskan quake focused its energy southeast
towards Yellowstone meaning that the stresses rippling through the
ground at Yellowstone were 200-300 times greater than if the quakes's
waves were aimed elsewhere. So when you think that a super volcano
eruption is due anytime now in the Yellowstone park it makes one wonder
just what exactly would it take to set the super volcano eruption
off?
Information courtesy of the BBC
*****************************
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Toba caldera- Sumatra
- Yesterday
One
Super volcano that has, however, been identified is Lake Toba in Sumatra.
The 'Lake Toba' Super volcano exploded ± 75 000 years ago covering
the entire planet with volcanic clouds. The result was radical for
planet. The clouds were loaded with mineral that deflected the sunlight
and caused the temperature of the planet to drop globally by ±5
degrees F and at certain latitudes, by ± 15 degrees F (Some
estimates put the average world widedrop in temperature to be about
21 degrees). An estimated 75 per cent of the northern hemisphere's
plants are thought to have died. Six years of this dramatic cooling
triggered a thousand-year ice age causing a volcanic winter but most
importantly it all but eradicated the human race, such as it was at
the time, from the face of the planet.
Following various studies (see below) scientists estimate that following
the 'Lake Toba' Super volcano eruption the number of our ancestors
dropped to as low as ±5 to 10 thousand... in the whole world!
To corroborate this hypothesis geneticists, studying the Human DNA,
had realized that there is, in fact, very little variation in the
DNA of the 6 billion humans alive today and remarking this lack of
variety the geneticists undertook to elucidate this phenomenon. Due
to the fact the geneticists can study DNA mutation, allowing them
to chronicle all the major events of our past, they were able to establish
the fact that the Human race had experienced a catastrophic reduction
in the size of its population at a given point in its past. It appears
that a genetic 'Bottleneck' had occurred highlighting not only a radical
reduction in the human population but also that our collective DNA
had diminished in variety for some unknown reason.
The
reason was not long in finding. A geologist visiting a university
in North-central USA was attending a genetics seminar given by a geneticist.
At the end of the seminar the geologist was talking to the geneticist
and mentioned 'Super volcanos'. The geologist explained about the
Lake Toba super volcano eruption some 75 000 years ago and the scientists
were able to make the connection between the Lake Toba Super volcano
eruption and the cataclysmic reduction in variety of the human DNA,
estimated to have occurred some ± 70 000 ago as well! an so
it was established that the Lake Toba Super volcano eruption was responsible
for the volcanic winter, that lasted for an estimated 1000 thousand
years, and which lead to the near annihilation of the entire human
race and the modification of the human DNA today.
click to enlargen
The Lake Toba caldera is 18 x 60
miles (30 by 100 km) and has a total relief of 5,100 feet (1700 m).
The caldera probably formed in stages. Large eruptions occurred 840,000,
± 700,000, and 75,000 years ago.
The eruption 75,000 years ago produced the Young Toba Tuff. The Young
Toba Tuff was erupted from ring fractures that surround most or all
of the present-day lake. There have been no eruptions at Toba in historical
time. The area is seismically active with major earthquakes in 1892,
1916, 1920-1922, and 1987.
Conclusion - The future
The
Yellowstone super volcano is under close watch but what if the eruption
come from another, as yet unknown, supervolcano? What would the impact
be? What if the eruption came from a submarine supervolcano? The sizes
of the resulting Tsunamis would be such
that whole, densely populated (not to say overpopulated) regions of
our planet (Bangla Desh , Hong Kong, Japan, California, Europe...)
would be submerged.
The Lake Toba eruption produced the largest
eruption in the last 2 million years and even with this knowledge combined
with data from the other known supervolcanoes, the scientists have no way
of preparing for them, they have no precedence, no factual, historical data
to work from only projections and theories.
While
it is true that scientists have no idea exactly what the impact of
such an eruption would be it does not need imagining what the after
effect of such a cataclysm today would actually be. If the Yellowstone
super volcano explodes¹, or any other on this planet for that
matter, not only would virtually the whole of the USA be devastated
but the entire planet would be immersed in a volcanic winter lasting
perhaps another 1000 years. While it is true that there are 6 Billion
people alive today, much more than 75 000 years ago, the consequence
of such a cataclysm would put an enormous strain on the human race,
reshaping geographical and political boundaries,wasting global agriculture
and ruining whole economies.
(¹ Scientists are all apparently unanimous
in saying that it is not a case of 'if' a super volcano explodes but
'when')
Final word.
The
documentary drew to it's end on this rather pessimistic note leaving
the viewer to reflect on the future. It did tend to relegate everyday
worries to a secondary role. However the human being is a resilient
creature and the house payments have to be paid so, being an optimistic
soul I do not doubt that scientists are working on solutions at the
moment and we will not have to leave the earth to populate another
planet just yet.
Thanks.
A very special thanks to the NASA, the NOAA, the Yellowstone
national park for the technical data and of course the BBC,,
after having watched what was a very intriguing and interesting documentary,
for the idea. I have tried not to copy the script itself but be influenced
by the theme.
© Nicholas Richards 2004
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