volcanic eruption (nicholas chin ee karng)

DEFINITION

Volcanic eruptions happen
when lava and gas are
discharged from a volcanic
vent. The most common
consequences of this are
population movements as
large numbers of people are
often forced to flee the
moving lava flow. Volcanic
eruptions often cause
temporary food shortages
and volcanic ash landslides
called Lahar.

How Do Volcanic Erupt?

Deep within the Earth it is so hot that some rocks
slowly melt and become a thick flowing substance
called magma. Since it is lighter than the solid rock
around it, magma rises and collects in magma
chambers. Eventually, some of the magma pushes
through vents and fissures to the Earth's surface.
Magma that has erupted is called lava.

Some volcanic eruptions are explosive and others
are not. The explosivity of an eruption depends on the
composition of the magma. If magma is thin and runny,
gases can escape easily from it. When this type of
magma erupts, it flows out of the volcano. Lava
flows rarely kill people because they move slowly
enough for people to get out of their way. If magma is
thick and sticky, gases cannot escape easily. Pressure
builds up until the gases escape violently and explode.

How Do We Monitor
Volcanic Eruption

• Scientists use a wide variety of
techniques to monitor volcanoes,
including seismographic detection of
the earthquakes and tremor that almost
always precede eruptions, precise
measurements of ground deformation
that often accompanies the rise of
magma, changes in volcanic gas
emissions, and changes in gravity and
magnetic fields. Although not diagnostic
individually, these techniques, when
used in combination at well-monitored
volcanoes, have resulted in successful
predictions. At Pinatubo volcano
(Philippines) in 1991, a successful
forecast saved thousands of lives

The Most Dangerous Type Of Volcanic Eruption

• The most dangerous type of volcanic eruption is referred to as a 'glowing
avalanche'. This is when freshly erupted magma forms hot pyroclastic
flow which have temperatures of up to 1,200 degrees. The pyroclastic flow
is formed from rock fragments following a volcanic explosion , the flow
surges down the flanks of the volcano at speeds of up to several hundred
kilometres per hour, to distances often up to 10km and occasionally as far
as 40 km from the original disaster site.

Example Of Volcanic
Eruption-Mount Fuji

On December 16, 1707, scientists
recorded the last confirmed eruption of
Mount Fuji, Japan’s highest point. Fuji is
composed of several
overlapping volcanoes. The top two are
known as “Old Fuji” (Ko Fuji) and “Young
Fuji” (Shin Fuji). Fuji has erupted at various
times starting around 100,000 years ago—
and is still an active volcano today.
The damage—especially the deaths—from
these disasters, plus a tsunami, is hard to
untangle. But what can be attributed to
the Hoei eruption is the damage to homes
near Fuji. The tephra fallout also reduced
agricultural productivity in the region,
causing many people to starve to death.

1815 eruption of Mount • The 1815 eruption of
Tambora Mount Tambora was the
most powerful volcanic
eruption in recorded
human history, with
a Volcanic Explosivity
Index (VEI) of 7. The
eruption ejected 160–213
cubic kilometres (38–
51 cu mi) of material into
the atmosphere.[1] It is the
most recently known VEI-
7 event and the most
recent confirmed VEI-7
eruption.

Mayon Volcano
volcano, Philippines

• Popular with climbers and campers, the
volcano is the centre of Mayon Volcano
National Park (21 square miles [55 square
km]). There are large abaca plantations on
its lower slopes. There have been more than
30 eruptions recorded since 1616. An
eruption in 1993 caused 79 deaths.
Subsequent eruptions in 2000, 2006,
2009, 2014, and 2018 forced tens of
thousands of people in nearby villages to
evacuate. In December 2006, rains from
powerful Typhoon Durian caused
mudslides and floods at the foot of the
volcano that killed more than 1,000 people.
Its most destructive eruption was in 1814,
when the town of Cagsawa was buried and
approximately 1,200 people were killed.

1883 eruption • This 1883 eruption generated the
of Krakatoa loudest sound ever reported in
history. It was heard as far away
as Perth in Australia (around
1,930 miles away) and the island
of Rodrigues near Mauritius - a
whopping 3,000 miles from
Krakatoa!

• hen the volcano erupted, the
explosion fired up hot ash 50
miles into the air. The force was
about 13,000 times more
powerful than the bomb that
devastated Hiroshima in 1945.

• Official records held that 165
villages and towns surrounding
Krakatoa were destroyed and 132
more were seriously damaged.
Nearly 36,500 people died, and
many thousands injured, mostly
due to the vast tsunamis which
occurred following the explosion.