Yellowstone National Park is America’s first National Park; Ulysses S. Grant
signed a law in 1872 stating it would be dedicated, and set apart as a public park or
pleasuring ground for the benefit and enjoyment of the people. It is located in three
different states: Wyoming, Montana, and Idaho. It is the largest National park in the
lower 48 states encompassing about 2,221,776 acres. Located on the continental
divide in the Rocky Mountains, the national park sits at 8,000 feet above sea level.
This is a popular spot for many people around the globe, with more than 3,000,000
visitors every year. (Griffith, Carr, 2012)
Long before any tourist had stepped foot in Yellowstone National Park, this
super volcano erupted, and sent massive amounts of lava, ash, and debris into the
atmosphere. This covered all the Western States, much of the Mid-West and
Northern Mexico, and some of the Eastern States.
The well-known “Old Faithful”
geyser in Yellowstone National Park is
proof that this super volcano is still active
and will one day erupt. This is the most
famous and celebrated geyser in the
world, and erupts an average of
Old Faithful Geyser
seventeen times per day. The eruptions
last between 1.5-5 minutes, and it reaches heights between 110-185 feet. It was
named “Old Faithful” from its frequent and predictable eruptions. For example, if it
erupted for less than four minutes the next eruption would happen 40-60 minutes
later; if it erupted for more than four minutes, it would be between 60-100 minutes
later. (Uhler, 1995)
Geysers have water circulating deep in the earth’s crust. Water temperatures
can exceed 200°F from the magma below; as the water boils the steam rises closer
to the narrow passages that connect to the surface. As the water gets hotter, and
boils faster the bubbles flowing through the passages get to large to pass freely,
when this occurs the bubbles lift the water above, causing the geyser to splash.
With the escape of some water the geyser loses pressure, which causes violent
boiling. An immense amount of steam forces water out, causing the eruption. Once
it begins to erupt the heat and pressure slowly decrease. It will stop when the water
reservoir is empty, or the gas bubbles can escape without lifting the water. (Good,
Pierce, 1998)
Yellowstone is a Caldera volcano, which are the most dangerous, and have
very violent eruptions. These volcanoes do not look like the usual ‘mountain shape’
volcano because of what is going on
underground. Under the surface, there is
Caldera volcano depression
a huge magma chamber that is creating an
extreme amount of pressure. This
pressure causes the ground to crack in
circular patterns, and after powerful
eruptions and the dissipation of pressure,
the circular cracks cave in, leaving large depressions in the crust. (Keller, 1998)
The reason this volcano formed lies deep under the crust in the mantle.
Material from the mantle is rising through the upper mantle and bringing heat to the
surface, which is called a ‘hot spot’. This hot spot raises right along the North
American Plate, this plate is moving about 1.8 inches per year in a southwest
direction, and as it moves, the material from the mantle accumulates, and sits under
the crust. The heat from the magma is melting the surrounding crust causing more
and more magma to accumulate. The crust is rich in feldspar and silica, when it
melts it contaminates the magma-forming felsic rich magma. Felsic rich magma
causes the most dangerous, and explosive eruptions.
This hot spot has been interacting with the North American Plate for nearly
17 million years, and there have been some catastrophic eruptions. The
Yellowstone super volcano has
erupted three times in its lifetime.
Read in National Geographic, the most
recent eruption happened about
640,000 years ago, with power a
thousand times stronger than Mount
St. Helens in 1980, this super
explosion is estimated to have shot
ash and debris 100,000 feet in the air. This buried much of the Western United
States, and down to the Gulf of Mexico. The Dense pyroclastic flow was superheated
to 1400° F, and destroyed everything in it’s path. The dense, hot material cooled
over the landscape; leaving nothing but hardened lava for miles. Yellowstone Lake
sits in the depression made from this eruption, and is the largest Alpine lake in the
world.
The largest eruption happened
about 2.1 million years ago. It was the
largest volcanic explosion in history, more
Yellowstone Lake
than doubling the intensity and strength of
the eruption 640,000 years ago. This
explosion sent over 600 cubic miles of rock
and ash into the atmosphere, gas mixing
with water vapor created sulfate aerosols,
dimming sunlight and drastically changing the climate around the world. This
explosion buried much of the United States in ash, the Western US ranged from 4-10
feet, and there were inches found all the way to the east coast. With all the magma
and pressure that escaped, the ground caved in leaving a depression 50 miles long,
and 40 miles wide. This eruption killed off much of the human population- it is
estimated it reduced to the thousands.
The smallest eruption coming from Yellowstone National Park happened
about 1.3 million years ago. Although it is the smallest, it exploded with
catastrophic results. (Achenbach, 2009)
This brings a question to mind, “When’s the next time it’ll erupt?”
Predictions have been made it could happen in the near future, since 2004 the
ground has been rising at an unusual rate. In the past three years alone it has raised
nine inches.
In an article it reads: if this massive super-volcano exploded, it would erupt
with power a thousand times stronger than Mt. St. Helens in 1980. Lava would be
pouring out, and ash would fan out and bury everything with ten feet of ash up to
1,000 miles away. Two-thirds of the US would be inhabitable from the toxic air,
millions of American’s would have no choice but to leave their homes, and air traffic
could be down for an extensive period of time.
However, scientists are unable to put a date on when this could happen, and
since the magma is nearly 6.5 miles below the surface, it brings more peace to mind.
They are unsure how full this cauldron will get before it erupts, it could be in the
near future-or centuries away. (Bates, 2011)
At a depth of about four hundred miles sits the ‘hot spot,’ which rises to
about 30 miles before spreading out to a width of three hundred miles. This is
where the volcano sits, waiting to explode. Since the conditions are so extreme, it is
hard to fully understand what is happening at these depths, but scientist think the
ground is rising due to the increase of magma 6.5 miles below the surface.
Yellowstone is a massive volcano, and if it erupted in this day and age it
would come with catastrophic consequences. Even though scientists are unable to
put a date on when this explosion will take place, we do know it brings millions of
tourists every year, and is a place that many people enjoy… for now.
References
Achenbach, J. “Will Yellowstone Blow Again?” National Geographic. 216 (2): 56-57
(2009)
Bates, D. “Could Yellowstone National Park’s caldera super-volcano be close to
eruption?” Mail Online. (2011)
Blanton, D. “Yellowstone National Park”. U.S. National Park Service Website.
Geology field notes. (2011)
Dzurisin, Christiansen, and Pierce. “VOLCANO HAZARDS FACT SHEET”. Yellowstone:
Restless Volcanic Giant. (1995)
Good, J. and Pierce, K. “Geysers”. Geology of Grand Teton & Yellowstone National
Park. (1998)
Griffith,C and Carr, F. “National Park Conservation Association”. Protecting
our parks. (2012)
Keller, E. “Caldera Volcanoes”. Extreme Science. (1998)
Uhler, J. “The Total Yellowstone Page”. Old Faithful Changes – Naturally
and Constantly. (1995)
Ward, D. “An overview of Yellowstone Geologic History”. Thermal Biology Institute
(TBI). (2006)