Yellowstone Volcano

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2004-8-10

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VOICE ONE:

This is Faith Lapidus.

VOICE TWO:

And this is Doug Johnson with EXPLORATIONS in VOA Special
English. Today we tell about Yellowstone National Park. It is one of
the most beautiful national parks in the United States. However, an
ancient and extremely violent volcano created the great beauty of
Yellowstone. The ancient volcano that formed Yellowstone is not
dead. It is only sleeping. And some experts say it could become very
dangerous in the future.

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VOICE ONE:

Yellowstone National Park is in
the western state of Wyoming. It is one of the most unusual places
in the world. Extremely hot water shoots out of the ground in
several hundred places. Small lakes contain water that is so hot it
is dangerous to come too close.

Visitors can watch bubbles coming up through boiling, hot mud.
They can see rocks that were once liquid and have cooled into
strange shapes.

Yellowstone is built on an ancient volcano. A lake of hot liquid
rock is about six kilometers under the park. This lake is about
sixty-five kilometers wide. Experts say this lake is under huge
amounts of pressure. The pressure and heat cause hot water to shoot
out of the ground and mud to boil at Yellowstone.

VOICE TWO:

The Yellowstone volcano has often been called a super volcano
because it is so big. Scientists believe major volcanic activity in
the Yellowstone area began about two million years ago. This
activity created violent explosions and built mountains and valleys.
Experts believe this super volcano had three major explosions called
eruptions. Each of those three eruptions may have been more powerful
than any in recorded history.

Each eruption threw out millions of tons of ash and rock. The
last eruption was so huge it covered much of North America with ash.
Some of this ash traveled high into the atmosphere and was carried
by strong winds around the world.

This cloud of volcanic ash circled the Earth many times. It
affected the climate by limiting the amount of sunlight that reached
Earth's lower atmosphere and surface. This last eruption formed the
mountains and valleys that visitors can see today in Yellowstone.

VOICE ONE:

When a volcano erupts, a huge amount of material explodes out of
the volcano. This leaves a giant circular hole in the ground, called
a caldera. Experts have known for many years that Yellowstone was
formed by volcanic activity. However they could not find the
caldera. Many experts searched a huge area in and around Yellowstone
Park looking for the remains of the caldera. A few years ago, the
National Aeronautics and Space Agency tested new satellite cameras.
They offered Yellowstone Park officials photographs of the park
taken from space.

VOICE TWO:

A national park expert was
extremely surprised when he looked at the photographs taken from
space. He immediately saw the caldera they had been searching for.
The photographs showed that Yellowstone National Park is the
caldera. The caldera is about seventy kilometers long and thirty
kilometers wide.

In fact, the park is a system of calderas formed within the past
sixteen million years. Experts now believe that as many fifteen or
twenty smaller eruptions also formed calderas.

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VOICE ONE:

Scientists know the volcanic heart of Yellowstone is deep within
the Earth. This area is called a hot spot. It is only one of a few
such places on Earth.

Extreme pressure deep in the Earth forces liquid rock up through
the hot spot to the lake of hot material that is below the surface.
This causes the extreme heat that is found in Yellowstone.

Scientists also know the Yellowstone hot spot is linked to the
activity of the North American plate. The North American plate is
one of several plates that make up the surface of the Earth. These
plates move a few centimeters each year. The hot spot does not move.
Very often the action between the hot spots and the plate causes
great earthquakes as plates move against each other. The plates
often split apart. And often after earthquakes, the hot spot forces
liquid rock to the surface. This has not happened for several
thousand years.

VOICE TWO:

The Yellowstone hot spot has been linked with the North American
plate for as long as seventeen million years. At many different
times, the hot spot has caused a kind of liquid rock called basalt
to explode to the surface.

This basalt rock from the Yellowstone hot spot can be found in
the western states of Washington, Oregon, California, Nevada and
Idaho. Evidence of this basalt rock can be found in an area as large
as three hundred twenty-two thousand square kilometers.

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VOICE ONE:

Yellowstone National Park is the oldest national park in the
world. About three million people visit it each year. Its great
natural beauty has made it one of the most popular national
parks.Most visitors like to see "Old Faithful", the world's most
famous geyser. A geyser shoots hot water high into the air. There
are more than three hundred geysers in Yellowstone.

Old Faithful is not the biggest or
the most beautiful geyser. But it is the most popular. Visitors
gather around Old Faithful before each eruption. Experts at the park
are able to predict when these will happen. The average time between
eruptions is about ninety minutes. Old Faithful shoots water an
average of forty meters into the air. This eruption lasts between
two and five minutes. Old Faithful releases up to about thirty
thousand liters of water into the air each time.

VOICE TWO:

The hot spot deep under the ground produces geysers like Old
Faithful. Old Faithful is evidence of the volcanic activity at
Yellowstone. But will the Yellowstone volcano erupt again? Most
experts think the answer is yes. But no one knows when. The most
recent of the three extremely powerful eruptions was about six
hundred fifty thousand years ago.

Experts say at least thirty smaller volcanic eruptions have taken
place at Yellowstone. Some of these were perhaps as big as the
nineteen ninety-one eruption at Mount Pinatubo in the Philippines.
Several are believed to have been much larger. The most recent of
these smaller eruptions took place about seventy thousand years ago.

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VOICE ONE:

Volcano experts say it is extremely difficult to tell when
Yellowstone might become an active volcano again. However,
earthquakes near a volcano are usually good evidence that a volcano
might become active again. For example, Mount Saint Helens in the
northwestern state of Washington exploded in nineteen eighty.
Several earthquakes took place near the volcano before that time. On
the morning that it exploded, Mount Saint Helens experienced an
earthquake of five point one on the Richter scale.

Yellowstone National Park experiences several thousand
earthquakes each year. Most are very small. They cannot be felt.
They can only be measured by scientific instruments. However, in
August of nineteen fifty-nine, an earthquake at Yellowstone measured
seven point five on the Richter scale. Twenty-eight people were
killed.

It was one of the strongest earthquakes ever recorded in the
United States. But Yellowstone's sleeping giant volcano did not
erupt.

VOICE TWO:

In two thousand one, the United States Geological Survey,
Yellowstone National Park and the University of Utah signed an
agreement.

That agreement established the Yellowstone Volcano Observatory.
Under the agreement, the park, the Geological Survey and the
university are responsible for improving efforts to study the
volcanic system of Yellowstone.

The observatory uses information from many different instruments
on the ground and from satellites to study the volcano. The
information will help officials decided if Yellowstone's huge
volcano is becoming a danger. Then they could warn the public
quickly if necessary.

Experts at the observatory say Yellowstone represents some danger
to the public. It always has. However, its natural beauty also makes
it a treasure that could not be possible without the sleeping giant
volcano that is under Yellowstone National Park.

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VOICE ONE:

This program was written by Paul Thompson. It was produced by
Mario Ritter. This is Doug Johnson.

VOICE TWO:

And this is Faith Lapidus. Join us again next week for another
EXPLORATIONS program in VOA Special English.


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