Transcript Living with a Volcano

By Alexia Louvieris
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Mount St Helens is a composite
volcano in the Cascade
mountains, 153 km south of
Seattle, Washington, USA.
Its major eruption happened on
the 18th of May 1980. 57 people
died and it caused millions of
dollars worth of damage to the
surrounding area. Hot ash and
rocks started forest fires and
melted the snow on caps of the
mountains. The resulting floods
and mudslides washed away
buildings, roads and houses. The
eruptions also spread a thick
layer of volcanic ash over a wide
area, destroying crops, wildlife
and blanketing cities.
This is the eruption in 1980. The pillar of
ash moved eastward, growing into a vast
dark cloud that plunged towns 85 miles
away into darkness. Most of northern
Idaho, western Montana, and eastern
Washington came to a halt because of the
ash fall.
In 1980 it was the first time it was
possible for volcanologists to use
modern technology to monitor Mount
St. Helens as it built up to its eruption.
They gathered lots of information and
data, but it was still impossible to say
the exact time it would erupt.
It had been dormant for 123 years. On
20th of March a series of small
earthquakes shook the region. The
following few days the magnitude and
frequency shock waves began to
increase and then the small gas
eruptions began, they observed these
as erupting volcanoes give off large
amounts of sulphur dioxide gas
beforehand. Volcanologists regarded
the volcano as a hazard. Warnings
were issued to citizens in the area and
mountain roads were
closed.Thousands evacuated the area
and their lives were saved.
Volcanologists installed highly
sophisticated equipment on the
mountain. They constantly
monitored the chemical
composition of groundwater
and escaping gasses, they
used laser surveying
techniques to look for any
expansion of the ground, and
recorded the constant seismic
activity. The side of the
mountain was clearly beginning
to expand as pressure began to
increase. By late April there
was a bulge 1000m wide and
over 2000m long. It was rising
at a steady rate of about 1.5m
every day as the mountain
began to fill with magma being
forced up from below.
This is the lava dome in Mount St.
Helens before it erupted.
The eruption started with an
earthquake which had a
magnitude of 5 on the Richter
scale. The pressured magma
exploded and flattened forests.
The speed of moving air and
debris overtook cars and
people as they tried to escape.
Superheated steam and ash
caused mudflows and
ashclouds were formed,
burning everything in their
paths.
If the 1980 eruption follows the
patterns of the previous
eruptions, it will be active for
the next ten to twenty years,
before it quietens down.
This is what Mount St. Helens looked like before the eruption. It
reduced its height from 2,950 metres to...
...2,569 metres. This is what Mount St. Helens and its
surroundings looked like after the eruption.
Mount Vesuvius is a complex
volcano in southern Italy, about
11km south-east of the city of
Naples. It is a cone within the
rim of Mount Somma, a large
crater formed when the top of
the mountain collapsed in the
eruption in 79AD.
It is the only active volcano on
the mainland of Europe. It has
been studied more than any
other volcano because it erupts
frequently and is easy to reach.
The top of the active cone is a
cup-shaped crater, ranging from
15 to 120 metres across.
Mt. Vesuvius's most famous
eruption was in 79 A.D. when it
destroyed the cities of
Herculaneum and Pompeii.
When Vesuvius erupted it
covered the cities of
Herculaneum and Pompeii with
20 feet of volcanic debris.
During this eruption about
2000 people were killed. That
eruption was called a plinian
explosion. This means that
extremely gas-rich, viscous
magma explodes deep inside a
volcano and a blast shoots
straight up at twice the speed
of sound, creating a vertical
column of ash as much as 20miles high. Since then it has
erupted over 50 times and is
still active.
Bird’s eye view of Mt.
Vesuvius.
The height of Vesuvius
changes with each eruption.
In 1900 it was 1,303 metres
high but after several
eruptions, its height dropped
to 1,227. Vesuvius spouts
columns of steam, cinders,
and sometimes small
amounts of lava into the air.
Many people live on the
lower slopes of the mountain
and on the plains at its foot,
in spite of Vesuvius' history of
disastrous eruptions. The
volcanic soil is extremely
fertile and the area is famous
for its vineyards of wine
grapes.
Mt. Vesuvius is still active
today. Its last recent eruption
was in 1944. About 2 million
people live near Mt. Vesuvius
and they could be in danger.
However, a plug indicates that
the once-threatening magma
deep below Vesuvius has
cooled and hardened into a
dormant, harmless mass.
But the plug’s presence also
means that the next eruption is
likely to be explosive
producing, deadly, avalanchelike pyroclastic flow of gas,
rocks, and hot ash, rather than
an eruption of hot but slowmoving lava, which is less
dangerous.
No volcanologist knows when
exactly Mt. Vesuvius will
erupt, but they know it might
erupt any time soon as it is
active. It has erupted many
times before, so there is no
saying that it won’t.
Volcanologists are using
seismographs, which are very
accurate when for-telling
eruptions. They monitor the
force and direction of
earthquakes, as most
eruptions start off with one or
even many earthquakes. The
history of eruptions also helps.
The crater of Vesuvius.
The people of Pompeii were
wiped out by this eruption.
The volcano blew on the
24th of August at 1pm. The
day darkened and soon it
was raining pumice stones
on the city. The roofs on
buildings collapsed, killing
people and doorways were
blocked. A man called Plinny
the Younger recorded these
events. He noticed a cloud
of molten rock and ashwhich today is known as a
pyroclastic surge. It’s so hot
it burns people instantly.
Bodies lay under 25m
metres of debris.
The ruins of Pompeii.
THIS SLIDESHOW IS MADE FOR PRIMARY SCHOOL
CHILDREN!!!
WHAT IS A VOLCANO????
A volcano is an
opening in the
earth’s surface.
It is in
mountain
the edge
tectonic
When they
erupt, gases,
rock fragments
and lava burst
out.
the form of a
as they are on
of the earth’s
plates.
HOW DOES A VOLCANO WORK????
•MOUNT ST HELENS
IS A VOLCANO IN
WASHINGTON, USA.
•IT’S MAJOR
ERUPTION
HAPPENED IN MAY
1980.
•57 PEOPLE DIED
IN THE ERUPTION
AND NEARBY TOWNS
WERE SERIOUSLY
DAMAGED.
• MOUNT VESUVIUS
IS A VOLCANO,
NEAR NAPLES IN
ITALY.
• ITS MOST
FAMOUS ERUPTION
HAPPENED IN
79AD.
• IN THAT
ERUPTION, ALL
THE CITIZENS OF
POMPEII WERE
BURNT OR
KILLED.
Tectonic plates - the
earth’s crust is broken up
into pieces. These pieces
are called plates. Imagine
the earth as an apple. The
earth’s crust would be the
apple’s skin.
Erupt - burst out suddenly
or dramatically
Magma - lava when it is
underground
I HOPE YOU HAVE ENJOYED MY SLIDESHOW