What is a volcano?
A volcano is a vent or 'chimney' that connects molten rock
(magma) to the Earth's surface. It includes the surrounding cone
of built-up material. Magma erupting from a volcano is called
lava. Gases and pieces of rock erupt from volcanoes too.
A volcano is active if it erupts lava, releases gas or shows
seismic activity. It is dormant if it hasn't erupted for a long time
but could again one day. An extinct volcano will never erupt
The explosiveness of a volcanic eruption depends on how easily
magma can flow and the amount of gas trapped in it. Large
amounts of water and carbon dioxide are dissolved in magma.
They behave like gas in fizzy drinks. After opening the bottle
the gas expands, forming bubbles that escape. This also
happens when magma rises quickly through the crust - gas
bubbles form and expand up to 1000 times their original size.
WHAT IS VOLCANIC ERUPTION ?
It is the sudden occurrence of a
violent discharge of steam and
volcanic material like volcanic
bombs, lapilli, ash and lava are
expelled violently in the land air and
List of active volcanoes in the Philippines
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Active volcanoes in the Philippines, as categorized by the Philippine Institute of
Volcanology and Seismology (PHIVOLCS), include volcanoes in the country having
erupted within historical times (within the last 600 years), with accounts of these
eruptions documented by man; or having erupted within the last 10,000 years
(holocene) based on analyses of datable materials. However, there is no consensus
among volcanologists on how to define an "active" volcano. As of 2012, PHIVOLCS
lists 23 volcanoes as active in the Philippines, 21 of which have historical eruptions
and two strongly fumarolic volcanoes - Cabalian and Leonard Kniaseff.[not in citation
given]; the Smithsonian Institution's Global Volcanism Program categories 20
Philippine volcanoes as "historical" and 59 as "holocene".
The Smithsonian Institution's Global Volcanism Program (GVP) list volcanoes with
historical, Holocene eruptions, or possibly older if strong signs of volcanism are still
evident through thermal features like fumaroles, hot springs, mud pots, etc. GVP
currently lists 50 Philippines volcanoes. The eruptions from the table below were
based more on GVP which gives a more detailed eruption history for a particular
mountain. The frequency of Historical Eruptions are based on definite historical
eruptions and excludes questionable or Uncertain accounts based on the two sources
The list below shows 25 active volcanoes in the Philippines was based more on the
PHIVOLCS list with some included from the GVP list. The number is not a definite
number and could depend on someone's definition of "active" or historical
timeframe. Also, volcanoes listed as inactive or potentially active could renew
activity after long periods of dormancy such as Mount Pinatubo in 1991
Active volcanoes in the Philippines
2,329 metres (7,641 ft)
1,080 metres (3,540 ft)
and Current Status
Explosions in 1952 is
with solfataras and
recorded in 1831, 1860
and 1913. Askedna Hot
Springs is located in
the southern base of
2,158 metres (7,080 ft)
uncertain during the
mudflows of 1730,
1743, 1843 and 1909.
1,301 metres (4,268 ft)
Phreatic eruption in
1939. Fumarolic with
Eruptions years are
from 1886 to 2011.
Eruption in 1860 and
activity in 1907.
Thermal areas are
located near the
summit and NW to
1,565 metres (5,135 ft)
1,133 metres (3,717 ft)
Its only recorded
eruption was in
1773, 1856, 1900,
1952, 1969 and
volcano till 1952
Eruption in years
1827, 1862, 1871
was in 1454.
Seismic swarm in
Davao del Norte
Lanao del Sur
The eruption in
eruption in 1897.
Listed as Bud
Dajo, a cinder
cone on Jolo
Island, in the
1886 to 2006.
was dated as
recorded in 1865
and 1882. The
1856 and 1858
646 metres (2,119 ft)
fumarolic on March
7, 1911, but if an
Thermal springs in
recorded from 1616
Eruptions in 1866 &
1867. Strong seismic
swarm in 1976.
on January 4, 1641.
Reawakened in 1991
producing the 2nd
largest eruption in
the 20th century.
Followed by milder
eruptions in 1992
Lanao del Sur,
are from 1765 to
were uncertain in
1915 and 1916.
Last activity was
the formation of
around 1350 AD
+/- 100 years
are from 1652 to
Claro on the GVP
Eruption years is
from 1572 to
signs of unrest
since 1991 and
eruptions in 1773,
1850 and 1854.
When does the volcanic eruption happen?
Volcanic eruptions happen when lava and gas are discharged from a
volcanic vent. What is the cause of volcanic eruption? Volcanic eruptions are caused
when magma from the magma chamber of the Earth rises up the pipe and out of the
vent. Magma is continuously supplied from the mantle of the Earth. Shield volcanoes
usually have a gentle eruption, as it contains basic lava. Acid-lava and composite
volcanoes usually have a violent eruption as it contains acidic lava. The vent of the
volcano might also be blocked, causing the magma to force its way out thus causing a
During a volcanic eruption, lava, tephra (ash, lapilli, volcanic bombs and blocks), and
various gases are expelled from a volcanic vent or fissure. Several types of volcanic
eruptions have been distinguished by volcanologists. These are often named after
famous volcanoes where that type of behavior has been observed. Some volcanoes may
exhibit only one characteristic type of eruption during a period of activity, while others
may display an entire sequence of types all in one eruptive series.
There are three different metatypes of eruptions. The most well-observed are magmatic
eruptions, which involve the decompression of gas within magma that propels it
forward. Phreatomagmatic eruptions are another type of volcanic eruption, driven by
the compression of gas within magma, the direct opposite of the process powering
magmatic activity. The last eruptive metatype is the phreatic eruption, which is driven
by the superheating of steam via contact with magma; these eruptive types often exhibit
no magmatic release, instead causing the granulation of existing rock.
Within these wide-defining eruptive types are several subtypes. The weakest are
Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The
stronger eruptive types are Pelean eruptions, followed by Plinian eruptions; the
strongest eruptions are called "Ultra Plinian." Subglacial and phreatic eruptions are
defined by their eruptive mechanism, and vary in strength. An important measure of
eruptive strength is Volcanic Explosivity Index (VEI), a magnitudic scale ranging from 0
to 8 that often correlates to eruptive types.
Volcanic eruptions arise through three main mechanisms:
Gas release under decompression causing magmatic eruptions.
Thermal contraction from chilling on contact with water causing phreatomagmatic
Ejection of entrained particles during steam eruptions causing phreatic eruptions.
There are two types of eruptions in terms of activity, explosive eruptions and effusive
eruptions. Explosive eruptions are characterized by gas-driven explosions that propels
magma and tephra. Effusive eruptions, meanwhile, are characterized by the
outpouring of lava without significant explosive eruption.
Volcanic eruptions vary widely in strength. On the one extreme there are effusive
Hawaiian eruptions, which are characterized by lava fountains and fluid lava
flows, which are typically not very dangerous. On the other extreme, Plinian eruptions
are large, violent, and highly dangerous explosive events. Volcanoes are not bound to
one eruptive style, and frequently display many different types, both passive and
explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt
vertically from a single crater near their peak, either. Some volcanoes exhibit lateral and
fissure eruptions. Notably, many Hawaiian eruptions start from rift zones, and some
of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed
that pulses of magma mixed together in the chamber before climbing upward -- a
process estimated to take several thousands of years. But Columbia University
volcanologists found that the eruption of Costa Rica‘s Irazú Volcano in 1963 was likely
2. Phreatomagmatic eruptions
Magmatic eruptions produce juvenile clasts during explosive decompression from gas
release. They range in intensity from the relatively small lava fountains on Hawaii to
catastrophic Ultra Plinian eruption columns more than 30 km (19 mi) high, bigger than
the AD 79 eruption that buried Pompeii.
Phreatomagmatic eruptions are eruptions that arise from interactions between water
and magma. They are driven from thermal contraction (as opposed to magmatic
eruptions, which are driven by thermal expansion) of magma when it comes in contact
with water. This temperature difference between the two causes violent water-lava
interactions that make up the eruption. The products of phreatomagmatic eruptions are
believed to be more regular in shape and finer grained than the products of magmatic
eruptions because of the differences in eruptive mechanisms.
There is debate about the exact nature of phreatomagmatic eruptions, and some
scientists believe that fuel-coolant reactions may be more critical to the explosive nature
than thermal contraction. Fuel coolant reactions may fragment the volcanic material
by propagating stress waves, widening cracks and increasing surface area that ultimetly
What Causes Volcanoes?
To understand what causes volcanoes, you need to understand how the earth is made
up. The earth has three main layers: the crust, the mantle and the core. The crust is made
up of solid rock and varies in thickness. It is more than 60km thick under mountain
chains like the Alps and Himalayas, but just 5km under the oceans. The mantle is a thick
layer of molten rock (called magma), and the core is made up of an outer liquid layer
and a solid centre.
Temperatures inside the earth are very high – over 5000‘C in the core. This means that
the planet on which we live is like a huge fiery ball of hot molten rock, surrounded by a
few kilometers of relatively cool, hard rock – the crust. Because heat rises, the magma in
the earth‘s mantle has to find a way to rise upwards though the crust above it, rather
like the way that hot air rises.
An erupting volcano
A volcano erupts when magma escapes from inside the earth. As the magma is escaping
from a confined space, a lot of energy is released with it, as happens with any other
explosion. This is why many eruptions also produce huge quantities of gases and dust.
Magma sometimes rises under enormous pressure, so it not only finds cracks in the
earth‘s crust, it can also create them. When magma reaches the earth‘s surface it is called
Tectonic plates and volcanoes
The earth‘s crust is its thinnest layer. It is broken up into large pieces, called tectonic
plates. These plates lie above the hot, liquid mantle. Each plate contains some
continental crust (land) and some oceanic crust (sea-bed). Huge currents of molten rock
This is no coincidence. Plate boundaries are among the most geologically active places
on earth. Here, new rock is being both created and destroyed, so this is where most of
the world‘s volcanic eruptions and earthquakes occur.
The Pacific ‘Ring of Fire’
More than half of all the world‘s volcanoes are found in the Pacific ‗Ring of Fire‘. This
area forms a circle stretching down the eastern side of the Pacific Ocean, from Alaska in
the north, through the Rocky Mountains of Canada and the USA, to the Andes
mountains of South America. It loops back around the western side of the Pacific, up
through New Zealand, Indonesia and Japan. Many of the world‘s most famous
volcanoes are found in this ‗Ring of Fire‘: Cotopaxi in Ecuador, which last erupted in
1928; Mount St Helens in the USA, which erupted spectacularly in 1980; and Krakatoa in
Indonesia, which killed 36000 people when it erupted in 1883.
Some plate boundaries follow the line of the land surface. For example, the eastern edge
of the Pacific Plate seems to run down the coast of the American continent. Others are
found at the bottom of the world‘s oceans. Here, hidden from view, lie extensive ranges
of mountains, canyons and volcanoes. New rock is being created here by volcanoes
spewing out lava underwater. Scientists estimate that between 2-5 cm of new crust is
created each year by volcanoes along the Mid-Atlantic Ocean Ridge.
How do volcanoes effect the weather?
The first is how the weather near an erupting volcano is being affected. The second is
how large eruptions will affect the weather/climate around the world. I think more
people are worried about the second issue than the first. As far as we know, the main
effect on weather right near a volcano is that there is often a lot of rain, lightning, and
thunder during an eruption. This is because all the ash particles that are thrown up into
the atmosphere are good at attracting/collecting water droplets. Another problem in
Hawaii is that involves the formation of volcanic fog. The ongoing eruption is very
quiet, with lava flowing through lava tubes and then into the ocean.
How do volcanoes effect people?
Volcanoes affect people in many ways, some are good and some are not. Some of the
bad ways are that houses, buildings, roads and fields can get covered with ash. As long
as you can get the ash off (especially if it is wet), your house may not collapse, but often
people leave because of the ash and are not around to continually clean off their roofs. If
the ash fall is really heavy it can make it impossible to breathe.
The good part of volcanoes
The main good effect that volcanoes have on the environment is to provide nutrients to
the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants,
and if it is very fine ash it is able to break down quickly and get mixed into the soil.
Key Facts About Preparing for a Volcanic Eruption
You can do many things to protect yourself and your family from the dangers a
volcanic eruption can cause. The best way to protect yourself and your family is
to follow the advice of local officials. Local authorities will give you
information on how to prepare for a volcanic eruption, and if necessary, on
how to evacuate (leave the area) or take shelter where you are.
How to prepare
Be prepared either to shelter or to evacuate. Develop an evacuation plan and a sheltering plan
for yourself, your family, and others in your household. Review the plans and make sure that
everyone understands them. If you haven‘t already done so, put together an emergency
supply kit . Supplies should include the following:
Flashlight and extra batteries
First aid kit and manual
Emergency food and water
Manual (nonelectric) can opener
Respiratory (breathing) protection
Eye protection (goggles)
Exposure to ash can harm your health, particularly the respiratory (breathing) tract. To
protect yourself while you are outdoors or while you are cleaning up ash that has gotten
indoors, use an N-95 disposable respirator (also known as an ―air purifying respirator‖). N-95
respirators can be purchased at businesses such as hardware stores. It is important to follow
directions for proper use of this respirator. For more information, see NIOSH-Approved
Disposable Particulate Respirators (Filtering Facepieces) . If you don‘t have an N-95
respirator, you can protect yourself by using a nuisance dust mask as a last resort, but you
should stay outdoors for only short periods while dust is falling. Nuisance dust masks can
provide comfort and relief from exposure to relatively non-hazardous contaminants such as
pollen, but they do not offer as much protection as an N-95 respirator. Cleanup or emergency
workers may need a different type of breathing protection.
If you are told to evacuate
Follow authorities‘ instructions if they tell you to leave the area. Though it may seem
safe to stay at home and wait out an eruption, doing so could be very dangerous.
Volcanoes spew hot, dangerous gases, ash, lava, and rock that are powerfully
Preparing to evacuate
• Tune in the radio or television for volcano updates.
• Listen for disaster sirens and warning signals.
• Review your emergency plan and gather your emergency supplies. Be sure to pack at least
a 1-week supply of prescription medications.
• Prepare an emergency kit for your vehicle with food, flares, booster cables, maps, tools, a
first aid kit, a fire extinguisher, sleeping bags, a flashlight, batteries, etc.
• Fill your vehicle‘s gas tank.
• If no vehicle is available, make arrangements with friends or family for transportation, or
follow authorities‘ instructions on where to obtain transportation.
• Place vehicles under cover, if at all possible.
• Put livestock in an enclosed area. Plan ahead to take pets with you, but be aware that
many emergency shelters cannot accept animals.
• Fill your clean water containers.
• Fill sinks and bathtubs with water as an extra supply for washing.
• Adjust the thermostat on refrigerators and freezers to the coolest possible temperature. If
the power goes out, food will stay cooler longer.
As you evacuate
• Take only essential items with you, including at least a 1-week supply of prescription
• If you have time, turn off the gas, electricity, and water.
• Disconnect appliances to reduce the likelihood of electrical shock when power is restored.
• Make sure your automobile‘s emergency kit is ready.
• Follow designated evacuation routes—others may be blocked—and expect heavy traffic
If you are told to take shelter where you are
Keep listening to your radio or television until you are told all is safe or you are told
to evacuate. Local authorities may evacuate specific areas at greatest risk in your
Close and lock all windows and outside doors.
Turn off all heating and air conditioning systems and fans.
Close the fireplace damper.
Organize your emergency supplies and make sure household members know where
the supplies are.
Make sure the radio is working.
Go to an interior room without windows that is above ground level.
Bring your pets with you, and be sure to bring additional food and water supplies for
It is ideal to have a hard-wired (non-portable) telephone in the room you select. Call
your emergency contact—a friend or family member who does not live near the
volcano—and have the phone available if you need to report a life-threatening
condition. Remember that telephone equipment may be overwhelmed or damaged
during an emergency.