Mount Merapi
Introduction
Mount Merapi is one of Indonesia’s most active volcanoes; it
is located between central java and Yogyakarta. It rises 2930m high above sea
level and has been active since the 1500’s. It is approximately 28km north of
Yogyakarta city where thousands of Indonesians live, many towns and villages
can also be found at the base or on the volcano itself, putting the villages
1700m above sea level. Smoke can be seen from the crater for roughly 300 days
of the year hence Merapi is translated as “mountain of fire”.
The volcano
Mount Merapi is located along a
subduction zone of the Eurasian plate and the indo-Australian plate which
pushes sediment up allowing magma to rise up and makes Merapi a composite/stratovolcano.
It has steep sides unlike shield volcanoes and it is built from layers of
fallen tephra, ash, rubble and hardened lava. The lava produced by Merapi has
high-intermediate levels of silica making it very viscous and classifying it as
adesitic lava, because of the high viscosity it rarely creates devastating lava
flows, but as a result of that it does generate large gas build up so when it
erupts it ejects a lots of ash into the atmosphere often reaching heights of
5km and radii of 30km, this often means villages as far away as 15km often get
blanketed in thick ash. Occasionally lahars and mudflows can be produced
because Indonesia in a country abundant with rainforest it obviously receives a
lot of rainfall, creating mudflows or super-hot lahars which are a mixture of
mud, water, hot ash and other debris that obliterates anything. The high pressures also release volcanic
bombs and hot gases approximately 800 Celsius, these explosive features make
its eruptions Plinean, but whereas Plinean often implies infrequent eruptions
Merapi differs as it erupts frequently with its most powerful eruptions having
a five- ten year gap from previous and
the not so powerful occurring every other year (approximately) it has gotten
much more active over the years with only a handful of eruptions in the 1800’s
and over double in the 1900’s.
Positive effects
of the volcano
Focusing mainly on most recent
eruptions of 2010 and 2006 Merapi does generate some notable positive impacts,
following the 2010 eruption the government set up and exclusion zone in the
cangkringan district meaning people in
the 9 villages there were rehomed to safer locations and will protect them in
the future. In 2004 6410 hectares surrounding the volcano was declared a
national park this not only restricts infrastructure which would be damaged in
future eruptions but also allows for recreation during clam periods. Ash from
the volcano will make the volcano more fertile in the future helping the
farmers produce higher crop yields; the area now notorious for volcanic
activity generates tourism from volcano enthusiasts which also provides year
round secure jobs for locals. Furthermore the sulphur produced from the volcano
can be mined and sold despite its harmful effects on the human body and since
Indonesia is developing the safety precautions won’t be as thorough so this has
a negative tied to it sadly.
Negative effects
of the volcano
Evacuation is a primary response to volcanic activity or
earthquakes and this displaces thousands of residents yearly even more so in
some years, in 2006 eruption 17,000 were evacuated, this is a huge
inconvenience socially as it disrupts school life but also economically as
business shut temporarily and income isn’t generated. The death tolls from
mount Merapi’s eruptions are huge as the government isnt
as well equipped to deal with the disasters as developed governments, the poor
responses can sometimes put pressure on the political parties to do more or
invest in better precautions and management strategies. The damage the volcano
causes leaves a huge impact environmentally as the national park gets damaged,
animals and their habitats destroyed and plant life killed. Furthermore
economically as homes and volcanic measuring equipment is destroyed along with
cars and shops too.
Management/prediction
of eruptions
The Indonesian government along with many world scientists
use Merapi for study and it therefore has a lot of equipment, seismic
monitoring began in 1924 and is still carried out today. During the 50’s-60’s
the stations faced starvation with equipment and monitoring was poor but
improvement began a decade later. After an eruption in 1994 a station and its
equipment was moved further back due to threat on the personnel. Magnetic field
measuring and tilt measurement are also used as small local changes in earth’s
magnetic field is seen near eruptions.
Managing the impacts
of eruptions
These management strategies are from the
largest most recent eruption of 2010, 210 evacuation centres were set up in
schools, churches, stadiums or tents. 1600 people as volunteers or army aided
in the national air response, international charities like the Red Cross also
help with aid. Formal evacuation centres are also permanently in place as
schools or stadiums might be out of use, government is providing financial
relief to farmers that have livestock killed. The government has set up a
special task force to deal with people suffering with family deaths or lost
jobs and destroyed property.
Mount St.Helens
Introduction
Mount St.helens is located in
skamania country, Washington, USA.
Before its infamous 1980 eruption it was the 5th highest peak
in Washington at a height of 1500m, but it is now only 1300m on its
north-eastern face and 1200m elsewhere, before 1980 its cone was 4 miles wide.
Mount st.helens is 96 miles south of Seattle, Washington and 50 miles north of
Portland, Oregon. Mount st.helens is part of the famous pacific ring of fire,
and due to its extensive snow cover during winter it is often nicknamed the
“Fuji-san” of America.
The volcano
Mount st.helens is also located along a
subduction zone of the Juan del fuca plate and the North American plate which
pushes sediment up high allowing magma to rise up from the asthenosphere and
makes st.helens a composite/stratovolcano. It also has steep sides and it is
built from layers of fallen tephra, ash, rubble and hardened lava. The lava
produced by st.helens has high-intermediate levels of silica making it very
viscous and classifying it as andesitic lava, because of the relatively high
viscosity it is unlikely to create devastating lava flows, but as a result of
that it does generate large gas build up so when it erupts it ejects a lots of
ash into the atmosphere and creates deadly pyroclastic flows as it did with the
famous 1980 eruption. Mount st.helens is
a very young volcano and only formed within the last 40,000 years, it very
rarely erupts and its last huge eruption was 3500 years ago. It exhibited
volcanic activity in 1800 and a few times in early 1900’s but no major
eruptions and being that its latest eruption was 2008 which was very small it
has a very high eruption frequency of about 100-150 years for considerable
eruptions. Due to the fact Mount st Helens goes off over large periods of times
the features of the eruption are deadly with rock, ash, steam and gases ejected
at speeds above 300mph, lahars often appear in the rivers surrounding st.helens
as the hot ash gets into the streams and travels long distances at speeds of
50mph wiping out anything in its path.
Positive effects
of the volcano
Referring to the 1980 eruption, scientists discovered after
entering the blast zones which were wiped flat and layered in ash that species
that burrowed underground and sheltered in small ridges, beetles were one of
the first animals to begin to colonize the area again and the landscape has
been reset for colonization of animal and plant life again. The study showed
that some animals (mainly insects) have the ability to survive in the harshest
of climates. The abundance of ash increased the fertility of soil and in fact
the area returned to normal state much quicker than scientists expected, which
could be due to the fertility of the soil. Lastly the eruption has now released
the volcano of huge pressures so we can be certain that a devastating eruption
like that is unlikely to happen in our lifetimes.
Negative effects
of the eruption
The eruption killed 57 people which doesn’t put such a toll
on the local economy but can affect the social lives of select few radically,
the damages caused by the eruption costed in total nearly $1 billion which
would put massive impact on local economy as bridges over the river toutle had
to be rebuilt costing $145 million, furthermore shipping in the Colombia river
was stopped this effected local economies elsewhere too, the same was for the
highways as well, up to 5000 motorists ha to abandon their cars. The
environment was the biggest loser in all this as 12million salmon were killed
by lahars and ash in the river, 7000 big game, and nearly all life in the
direct blast zone was destroyed and those in the sear zone would have habitat destroyed
and food supplies gone and with no safe drinking water the animals would have
starved if the survived the eruption.
Management/prediction
of eruptions
An exclusion zone was set up the march of the eruption in
May 1980, with red zones allowing no body to enter and blue allowing access for
farmers, the volcano is constantly monitored by the USGS for activity in which
to warn nearby residents. Geodetic networks are set up to measure the changing
shape of the volcanoes’ surface caused by pressure and magma builds up.
Electronic distance measurements, tilt measurements and standard levelling
surveying are used to measure change in the elevation and also looking for
cracks or openings. Measurements in magnetic fields, electrical conductivity
and gravity are also used to predict an eruption, changes in fumaroles or S02
are noted as they can indicate lava activity. Changes in groundwater and levels
are used to detect groundwater’s role in predicting/ generating eruptions.
Managing the
impacts of eruptions
The National Guard flew helicopter missions up
to two weeks after the eruption rescuing people in the blast zone and
elsewhere, they saved 130 people. Clean water, food supplies and medical
equipment was issued by the US government and charities. 2 million gas masks
were handed out to protect people from breathing in ash and asphyxiating or to
protect rescuers and charities from the poisonous S02 that was released. The
ash was cleaned up from all the towns using diggers, sweepers and trucks and
all the ash was gone from town areas within 3 days.
