Volcanism refer s to the ejection of molten materials from a
volcano. A volcano is a mountain or a hill in a restricted vent in the
earth’s crust. Through this vent, gases and other hot materials are
expelled. These ejected materials accumulate around the vent and
form volcanic cone forms. The top of the volcano is called the
According to the Philippine Institute of Volcanologist and
Seismology, there are 32 volcanoes in the Philippines. The most
famous and beautiful of these volcanoes is Mt. Mayon in Albay
Province. Volcanologists fear that this eruption has changed the
perfect cone shape of the volcano.
Volcanic products are materials that come out of a
volcano. These eruptive products are a mixture of gaseous,
liquid and solid materials
The fragments of magma quickly solidify and for
pyroclastic( meaning fire-broken) fragments. When the
fragments are from 2 to 64mm in size, they are called
lapilli. When they are smaller than 2mm, the fragments
are called ash. It refers to tiny, powderlike fragments.
The most abundant are water vapor, carbon
dioxide, sulfur dioxideand hydrogen sulfide.
Sample from present day volcanoes indicate the 50% to 80%
of all volcanism gases are water vapor, with lesser amounts
of carbon dioxide, nitrogen, sulfur gases, especially sulfur
dioxide and hydrogen sulfide.
Formation of Lava
Melting of solid rock to form magma is controlled by three
physical parameters: its temperature, pressure, and
The surfaces produced by lavaflows often reflect
their internal movement in relation to their congealing
crust. Sheet- and pahoehoe lava flows result in continuous
surfaces. Aa- and block flows result
indiscontinuous surfaces. The
terms "pahoehoe" and "aa" are Hawaiian words.
Pahoehoe lavas are thin. They flow smoothly and are often
formed by small volumes of hot, fluid basalt. The higher the
volume of lava emitted the faster the current. Pahoehoe
flows move forwards in tongues or lobes and are
characterized by a glassy, plastic skin. They may embrace
obstacles at a rate of about 50m an hour. When
the pahoehoe lava flow cools, it often solidifies to a
Sheet lavas emerge from fissure systems forming flows
commonly ranging between 10m and 30m in thickness. They
flow out so fast that vast volumes of basalt are discharged
over an enormous area. Featurelesslava plateaus are formed.
During the eruption of Roza, Oregon, 14 million years ago,
1500km3 of sheet lavas were produced in about a week.
Aa flows are emitted from the vent at high rates ranging
to 50km an hour, often with much lava fountaining. They
are characteristic of viscousmagmas. Aa flows are
animated with sporadic bursts of energy. They may push
down houses, walls and forests. However, the hallmark
of aa lava flows is the very rough surface it produces
when it cools and solidifies.
Magma - Molten rock beneath Earth's surface.
Parasitic Cone - A small cone-shaped volcano formed by an accumulation of
Sill - A flat piece of rock formed when magma hardens in a crack in a
volcano.Vent - An opening in Earth's surface through which volcanic materials
Flank - The side of a volcano.
Lava - Molten rock that erupts from a volcano that solidifies as it cools.
Crater - Mouth of a volcano - surrounds a volcanic vent.
Conduit - An underground passage magma travels through.
Summit - Highest point; apex
Throat - Entrance of a volcano. The part of the conduit that ejects lava and
Ash - Fragments of lava or rock smaller than 2 mm in size that are blasted
into the air by volcanic explosions.
Ash Cloud - A cloud of ash formed by volcanic explosions.
3. Mount Vesuvius, Italy-Vesuvius' eruption in 79 A.D. covered the
cities of Pompeii and Herculaneum, preserving them for generations to
come. But this eruption also holds a place in history because of its
documentation. Pliny the Younger left a detailed description of the event
in two letters to Tacitus. A type of eruption -- the Plinian type -- is named
for Pliny the Elder who died in the catastrophe. The volcano is still active
and has had several eruptions -- the most deadly being in 1631. Check
out this Mount Vesuvius page. Picture: UPI/Corbis-Bettmann |
4. Mount Tambora, Indonesia-The largest eruption during the last
two centuries, as well as the deadliest volcano in recorded history,
Mount Tambora exploded April 10-11, 1815. It killed an estimated
92,000 people. Almost 80,000 of the victims died of starvation brought
on by the agricultural devastation in the volcano's wake. The eruption
and the resulting massive clouds of dust and ash affected most of the
Northern Hemisphere, causing unusually cool temperatures and failed
crops in 1816 -- sometimes referred to as "the year without a
5. Mount Krakatau, Indonesia-On August 27, 1883, Mount Krakatau
exploded with such force that it was heard in Australia, over 2,000 miles
away. The force of the eruption triggered a series of tsunamis that
reached the Hawaiian islands and the coast of South America, killing
more than 36,000 people. The five cubic miles of ejecta covered the
surrounding areas in darkness for over two days and caused a series of
dramatic sunsets around the world throughout the following year. The
explosion and subsequent collapse of the volcano left only a remnant of
the island above sea level. By 1928, another small island had emerged
from a rising volcanic cone. Visit Krakatau, Indonesia.
6. Mount Pelee, Martinique-The eruption on May 8, 1902, killed 29,000,
destroying the port town of Saint-Pierre four miles away. Almost all the deaths
were caused by the resulting pyroclastic flow -- a deadly, fast-moving cloud of
hot gas and dense liquidized volcanic particles.Only two residents of the town
survived the flow. Volcanology (also called Volcanism) was at best a primitive
science in 1902, and the existence of pyroclastic flows was unknown. After this
disaster a "new" type of eruption was named after Mount Pelee - the Pelean-
type eruption. See Mount Pelee eruption.Photograph of the remains of St.
Pierre by Heilprin, 1902.
7. Parícutin, Mexico-In February 1943, a pile of ash began to rise from
a corn field near the town of Parícutin, Mexico. A mountain began to
emerge from the earth, reaching a height of 1,200 feet in one year.
Although the ensuing nine-year eruption resulted in the destruction of
the town of Parícutin, it presented the modern world with a remarkable
opportunity to see the birth of a volcano. Only three people died, all by
lightning associated with the eruption.
8. Mount St. Helens, Washington-One of the more highly publicized
and studied volcanic explosions, Mount St. Helens erupted on May 18,
1980. The volcano, which had been dormant since 1857, began
erupting steam after a series of earthquakes in March 1980. The 1978
prediction of the U.S. Geological Survey that violent and intermittent
volcanic activity would begin, "within the next 100 years, and perhaps
even before the end of this century," had come true. Luckily, close
study of St. Helens prevented a major loss of life. Even so, 60 deaths
resulted from the May 18 eruption. Learn more about Mount St. Helens.
9. Nevada del Ruiz, Colombia-Although the eruption of Nevado del
Ruiz (or Mount Ruiz) on November 13, 1985, was relatively small, the
ensuing mudslides caused by melting ice and snow resulted in the the
death of 23,000 people and the destruction of the town of Armero.
Most of the residents would have survived had they moved to higher
ground. This eruption brought attention to the fact that growing
numbers of people live within the danger zones of the world's
volcanoes. A larger eruption of Ruiz in 1845 killed about 700 people.
VisitNevada del Ruiz.
10. Mount Pinatubo, Philippines-Killing almost 800 and leaving an
estimated 100,000 homeless, Mount Pinatubo's eruption in June 1991
was 10 times larger than the Mount St. Helens' eruption and one of the
biggest of the 20th century. It emitted a cloud of smoke and ash over
19 miles high. The evacuation of more than 70,000 people and the
volcanic event were broadcast worldwide, making Pinatubo (in)famous
throughout the world. Learn more about Mount Pinatubo.
Signs that a volcano is going to erupt.
The temperature of rocks in the volcanic
Changes in shape of the volcanic cone. Most of
the time the cone starts to swell or bulge just
before a eruption.
A number of increases in small earthquakes or
tremors around a volcano
Emission of gas and steam from a volcano.
The disadvantages of living
near a volcano
When the volcano erupts it can
do many things such as:
-Destroy crops and plantation
-Suffocate people from the
The benefits of living near volcanoes
Volcanic ash makes extremely fertile soil. Grape vines particularly grow extremely well in
volcanic ash-soil, aside from other regular crops. The Ancient Romans realised this, which is
the reason a lot of Roman vineyards are surrounded by volcanoes. Today, grapes grown in
volcanic regions produce the best-rated wine on the globe.
Crops can grow very well in volcanic soil, even if water isn't so common!
Volcanic Tuff, Pozzolona, Ignimbrite, Obsidian, Volcanic Glass, Pumice and so on. These are
different rock variations formed by volcanoes and lava. Pozzolona for example is even tougher
than concrete, and was used in many official and royal buildings throughout the Roman and
Pumice was, and still is today, used for personal hygiene.
There is archaeological evidence that prehistoric man used volcanic rock to produce stronger
weapons and tools than standard stone.
- Geothermal Energy
Free, renewable, infinite energy and heat.
In Iceland, a quarter of the country's electricity is produced by harvesting geothermal energy
from its many volcanoes.
It's also used to heat water for heating and hygiene.
the Vikings, Romans and Greeks in particular harvested geothermal heat from volcanoes,
usually for public baths.
The Romans used geothermal heat to invent the worlds first central heating, by channelling the
geothermal heat through complex plumbing underneath houses to provide underfloor-
heating(however that would mean the settlement has to be really close to the source otherwise the heated
Volcanoes erupt and adventurers get lost in volcanic mountains. This provides jobs for
local people, as specialist rescue experts would need to be on hand at all costs.
Volcanic mountains and volcanic islands are amongst some of the most beautiful places
on Earth. They provide a peaceful, serene and relaxed scenery for all to enjoy (until it
erupts of course).
Tahiti and Bora Bora, islands surrounded by volcanoes, are considered to be paradise
Pretty much the same as Aesthetics. The stunning scenery attracts tourists. Tourists
bring money. Volcano country gets rich.
Volcanoes help us understand how Earth was born, the stages which it developed
through, the magnetic field and so on. Wherever there's an active volcano, a scientists
facility will be nearby. Of course aside from contributing to science, the scientists can also
predict when eruptions will occur, providing locals with enough time to evacuate.