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Chapter 6

Volcanoes

Introduction:- Like Earthquakes, Tsunamis, Tides and Clouds, Volcanoes are results

of another type of physical processes that take place inside the Earth. The word,

‘Volcano’ is named after the small island of Vulcano in the Mediterranean Sea of Sicily.

Vulcan is the blacksmith of the Roman Gods. Centuries ago the Romans believed that

Vulcano was the chimney of forge of Vulcan. It is believed that Vulcan used to prepare

weapons for Mars the God of wars on orders from Jupiter, the king of Gods. The molten

lava and the fragments that came out from the volcano, it is believed that they are from

the forge of Vulcan as he beat out thunderbolts in the preparation of weapons. The

people in Polynesia attributed the eruptive activity to the beautiful but wrathful Pele, the

Godess of volcanoes whenever she was angry or spiteful. The Maoris used to worship

Ruaumoko (see Fig. 3.1) the God of volcanoes and earthquakes in order to get

themselves protected from the fury of earthquakes and volcanoes.

6.3Many ancient accounts ascribe volcanoes to supernatural causes such as the

action of Gods or demigods. According to ancient Greeks, the capricious power of

volcanoes could only be explained as acts of Gods. The German astronomer, Johannes

Kepler (1571-1630) believed that volcanoes are the ducts for the earth’s tears. An early

idea counter to this was proposed by Jesuit Kircher (1602-1680), who witnessed the

eruption of Mount Etna and Stromboli, then visited the crater of Vesuvius and published

his view of an earth with a central fire connected to numerous others caused by the

burying of sulphur, bitumen and coal.

Today we know that there is nothing heavenly or divine in the earthquakes and

volcanoes. They are the result of physical processes that take place within the earth. A

volcano erupts and nobody on earth can stop it, that is, there is no prevention. Even

though it is disastrous, an erupting volcano is a beauty of nature.

As we talk of fire as a good servant and a bad master, volcanoes are the same.

They destroy and also they create. The awesome destructive power is revealed in the

catastrophic eruption of Mount St. Helens on 18 May 1980. But, for a long time

unknown to man, volcanoes have played a key role in forming and modifying the planet

upon which we live. According to geologists and oceanographers, about 75% of the

earth’s surface including that of the sea bed is of volcanic origin. It is believed that

gaseous emissions from volcanic vents over millions of years formed the earth’s oceans

and atmosphere, the vital necessities for human and animal life. The present majestic

land shapes and fertile soils are the results of several volcanic eruptions of the past.

6.1Going to the historical aspect of volcanoes, the eruption of Mount Vesuvius in Italy

on August, 79 AD is perhaps the earliest and the most famous volcanic eruption. It had

been dormant for generations, but when it suddenly exploded, it destroyed the Roman

cities of Pompeii, Stabiae and Herculaneum. Pompeii and Stabiae were buried under

ashes. Herculaneum was burnt under a mud flow. The volcano was almost extinct, but a

succession of earthquakes in 63 AD made one feel that it might erupt at any moment.

The one in 79 AD was a major one and repeated in the years 1631. 1794. 1872. 1906

and in 1944 in the midst of World War II.

In this chapter we shall briefly deal with the formation of volcanoes, its causes and

protection from the same.

REVIEW OF LITERATURE

A volcano! What is it?

6.2Volcanoes are cone-shaped hills or mountains around a vent connecting to

reservoir of molten rock, or magma below the surface of the Earth. Sometimes, the

molten rock is forced upwards by the pressure of the gas till it breaks through a weak

spot in the Earth’s crust. The eruption of magma is the lava and the same shoots into

the atmospheric air as clouds of lava fragments, ash and dust. The accumulation of

debris from eruptions causes the volcasno to grow in size.

6.3A volcano is an opening or rupture on the surface or crust of a planet which allows

hot magma, volcanic ash and gases to escape from the interior.

6.1Volcanoes, unlike mountains are built by the accumulation of their own eruptive

products - lava, bombs and volcanic ash. Volcano is essentially a conical hill or

mountain built around a vent that connects with the reservoir of molten rock below the

surface of Earth. In fact, the name volcano refers to the opening or vent through which

the products are expelled to the atmosphere.

The Physics of action of a volcano:

rocks being lighter than the surrounding solid rock, forces its way upward and tries to

find some weak point on the Earth’s crust and the eruption starts. The molten rock

comes out through the vent as lava and lighter ones may shoot out violently into the air

as thick clouds of lava fragments. Some larger and heavy ones fall back into the vent.

The lighter ones get accumulated around the vent. The accumulation of heavy

fragments around the vent start flowing downwards due to gravity. Some of the lighter

ejected ones are carried by the wind and later fall on the ground many kilometers away.

The finest gas-like particles escape to the atmosphere and may reach any part of the

globe by stratospheric winds before getting settled.

The magma consists of crystals, fragments of surround

dissolved gases, but it is basically a liquid composed mainly of oxygen, silicon,

aluminium, magnesium, calcium, sodium, potassium, titanium and manganese. After

getting solidified, it forms a huge magmatic rock.

Types of Volcanoes:- According to geologists, there are four main types of volcanoes.

They are:

(i) Composite Volcanoes:6.1Composite volcanoes also

known as Strato volcanoes are

some of the Earth’s grandest

mountains in the wcorld.

Majestic and very beautiful to

look at. They are built of

alternate layers of lava, volcanic

ash, cinders, blocks and bombs,

steep-sided, height about 8000

feet above the ground. They

have a crater at the given an

illustrative diagram of a

Fig. 6.1 Cross Section of a Composite

Volcano (Picture Credit : 6.3)

1. Large Magma chamber 2. Bedrock 3. Conduit pipe 4. Base 5. Sill 6. Dike

7. Layers of ash emitted by the volcano 8. Flank 9. Layers of Lava 10. Throat 11. Parasit

12. Lava flow 13. Vent 14. Crater 15. Ash cloud.


the products are expelled to the atmosphere.

The Physics of action of a volcano: - Due to buoyancy and gas pressure, the molten

han the surrounding solid rock, forces its way upward and tries to



f lava fragments. Some larger and heavy ones fall back into the vent.



by the wind and later fall on the ground many kilometers away.

like particles escape to the atmosphere and may reach any part of the

globe by stratospheric winds before getting settled.

The magma consists of crystals, fragments of surrounding un



getting solidified, it forms a huge magmatic rock.

According to geologists, there are four main types of volcanoes.

Composite Volcanoes: -

Composite volcanoes also

known as Strato volcanoes are

some of the Earth’s grandest

mountains in the wcorld.

Majestic and very beautiful to

look at. They are built of

alternate layers of lava, volcanic

ash, cinders, blocks and bombs,

out 8000

feet above the ground. They

have a crater at the given an

illustrative diagram of a

Fig. 6.1 Cross Section of a Composite

(Picture Credit : 6.3)

1. Large Magma chamber 2. Bedrock 3. Conduit pipe 4. Base 5. Sill 6. Dike

7. Layers of ash emitted by the volcano 8. Flank 9. Layers of Lava 10. Throat 11. Parasitic cone

12. Lava flow 13. Vent 14. Crater 15. Ash cloud.


Due to buoyancy and gas pressure, the molten

han the surrounding solid rock, forces its way upward and tries to



f lava fragments. Some larger and heavy ones fall back into the vent.



by the wind and later fall on the ground many kilometers away.

like particles escape to the atmosphere and may reach any part of the

ing un-melted rocks and



According to geologists, there are four main types of volcanoes.

Fig. 6.2 Cinder Cone Volcano (Credit : 6.4)

composite volcano and the same is shown in Fig. 6.1. Looking upon the past, these

volcanoes posed a great hazard to civilization because of the volcanic ash by an

explosive action. Famous composite volcanoes include Mount Fiji in Japan, Mount

Shasta and Mount Larsen in California, Mount St. Helens And Mount Rainier in

Washington State, Mount Hood in Oregon, Mayon volcano. In the Philippines, Mount

Etna, Mount Vesuvius and Stromboli in Italy and Mount Cotopaxi in Equador.

(ii) Cinder Cones:- 6.3Cinder Cones also known as Volcanic Cones are the result of

eruptions consisting of small pieces of scoria and pyroclastics. T

and hence the name. They get accumulated near the vent. These are due to short

eruptions creating a cone

volcano is shown in Fig. 6.2.

shaped crater. Here is an interesting episode in a village in Paricutin in Mexico where a

Cinder Cone started growing on a farm in 1943. The cone acquired a height of about

1200 feet. At the top of the cone was a funnel

Paricutin built a prominent cone covering about 100 square miles with ashes, and

destroyed the town of San Juan. Geologists from many parts of the world came to

Paricutin to study volcanism, its products and the modification of a v

erosion.

There are many Cinder Cone volcanoes in West

Mexico, the one in the middle of Crater Lake in Oregon, Sunset Crater in Arizona are

Cinder Cone Volcanoes. In New Mexico, Caja del Rio is a volcanic

Cinder Cones.

Fig. 6.2 Cinder Cone Volcano






us and Stromboli in Italy and Mount Cotopaxi in Equador.

Cinder Cones also known as Volcanic Cones are the result of

eruptions consisting of small pieces of scoria and pyroclastics. They resemble cinders

and hence the name. They get accumulated near the vent. These are due to short

eruptions creating a cone-shaped hill of some 300 to 400 m high. A Cinder Cone

volcano is shown in Fig. 6.2.

They usually erupt only once. But

sometimes form larger volcanoes. 6.1Cinder Cones are the simplest type of

volcanoes. They are built around a single

vent and forming the Fig. 6.2 Cinder Cone

Volcano (Credit:6.4) shape of a circular or

oval cone.

Most Cinder Cones



1200 feet. At the top of the cone was a funnel-shaped crater. In about 9 years time,



Paricutin to study volcanism, its products and the modification of a v

There are many Cinder Cone volcanoes in West-Northern America, Paricutin in


Cinder Cone Volcanoes. In New Mexico, Caja del Rio is a volcanic

Cinders






us and Stromboli in Italy and Mount Cotopaxi in Equador.

Cinder Cones also known as Volcanic Cones are the result of

hey resemble cinders

and hence the name. They get accumulated near the vent. These are due to short-lived

shaped hill of some 300 to 400 m high. A Cinder Cone

They usually erupt only once. But

sometimes form larger volcanoes.

Cinder Cones are the simplest type of

volcanoes. They are built around a single

vent and forming the Fig. 6.2 Cinder Cone

shape of a circular or

nder Cones have a bowl-



. In about 9 years time,



Paricutin to study volcanism, its products and the modification of a volcanic landform by

Northern America, Paricutin in


Cinder Cone Volcanoes. In New Mexico, Caja del Rio is a volcanic field of over sixty

(iii) Shield Volcanoes: -

volcano can grow to be very big. The

oldest continental regions of the Earth

are supposed to be the remains of Shield

Volcanoes. A diagram of a Shield

Volcano is shown Fig. 6.3. They are tall

and broad with flat rounded shapes and

have a large crater at the summit. They

are built due to countless out

from the vent. As no pyroclastic material acc

volcanoes are comparatively safe.

6.1Shield Volcanoes are built almost entirely of fluid lava. Several flows in all

directions build a domical shape looking something like a warrior’s shield hence the

name. The lava from such volcanoes consist mainly of Basalt lava. Some of the largest

volcanoes in the world are of this type with diameters 3 to 4 miles and height about

2000 feet. 6.3These volcanoes generally do not explode catastrophically. They are more

common in ocean in oceanic than in continental stings. There are many shield

volcanoes in the world. Mauna Loa, a Shield Volcano on the ‘Big’ island of Hawaii is the

largest single mountain in the world rising over 30,000 feet above sea level and about

100 miles across the base. The Kilauea in Hawaii and Olympus Mons of Mars and

some are in Iceland.

(iv) Lava domes:- 6.2Lava domes are made of viscous pasty lava squeezed like tooth

paste from a tube. 6.1The lava being too viscous gets spread around the neck of the

vent. The dome grows due to the thermal expansion taking place inside. As it builds up,

the outer ones cool and become hardened. Volcanic domes sometimes occur within the

craters. Examples of this type of volcanoes are: Mount Pelee in Martiniaue. Lesser

Antilles and Lessen peak and Mono domes in California.

An extremely destructive explosion accompanied the growth of a dome at Mount

Pelee in 1902. The coastal town of St. Pierre was demolished and about 30,000 people

were killed by the incandescent, high velocity ash f

Other type of Volcanoes: -

Fig. 6.3 A Shield Volcano

- 6.4A shield

volcano can grow to be very big. The

oldest continental regions of the Earth

remains of Shield

Volcanoes. A diagram of a Shield

Volcano is shown Fig. 6.3. They are tall

and broad with flat rounded shapes and

have a large crater at the summit. They

are built due to countless out-pourings

from the vent. As no pyroclastic material accompanies the out

volcanoes are comparatively safe.

Shield Volcanoes are built almost entirely of fluid lava. Several flows in all


uch volcanoes consist mainly of Basalt lava. Some of the largest


These volcanoes generally do not explode catastrophically. They are more

oceanic than in continental stings. There are many shield



ase. The Kilauea in Hawaii and Olympus Mons of Mars and

Lava domes are made of viscous pasty lava squeezed like tooth

The lava being too viscous gets spread around the neck of the

me grows due to the thermal expansion taking place inside. As it builds up,



essen peak and Mono domes in California.



were killed by the incandescent, high velocity ash flow and volcanic dust.

-

Lava flow

Crater

Fig. 6.3 A Shield Volcano (Credit : 6.4)

ompanies the out-pourings, these

Shield Volcanoes are built almost entirely of fluid lava. Several flows in all


uch volcanoes consist mainly of Basalt lava. Some of the largest


These volcanoes generally do not explode catastrophically. They are more

oceanic than in continental stings. There are many shield



ase. The Kilauea in Hawaii and Olympus Mons of Mars and

Lava domes are made of viscous pasty lava squeezed like tooth

The lava being too viscous gets spread around the neck of the

me grows due to the thermal expansion taking place inside. As it builds up,





low and volcanic dust.

Vent

(i) Super volcanoes:- 6.3lt is a large dangerous volcano with a large caldera and can

potentially produce devastation on an enormous, sometimes continental scale. Due to

the eruption of sulphur and ash, a global cooling effect is produced after many years of

eruption. Examples of this type of volcanoes are: Yellowstone Caldera in Yellowstone

National Park and Valles Caldera in New Mexico both in the western US. Lake Taupo in

New Zealand, Lake Toba in Sumatra in Indonesia and Ngorogoro Crater in Tanzania,

Krakatoa near Java, Sumatra, Indonesia,

(ii) Submarine Volcanoes:- “These volcanoes are situated in the ocean floor. Some of

them are active and some are not active. Those which lie in the deep ocean, the

explosion is prevented by the enormous quantity of water above. Those which lie in

shallow water, a mixture of sand and water enter through the vent and later come out

and again get mixed with the sand outside on the shore. The famous black sand in the

beaches of Hawaii is due to the submarine volcano in shallow waters. Geologists and

oceanographers have found the presence of spectacular high temperature hydrothermal

plumes and vents called “Smokers” in the deep ocean. 6.3These volcanoes are situated

in the ocean floor. Some are at great depths and some in shallow water. The deep

ocean volcanoes can be detected by hydrophones and also by the discoloration of

water because of volcanic gases. Pillow lava is a common emotive product of these

volcanoes.

(iii) Subglacial Volcanoes:- These are found underneath icecaps and called table

mountains. They are made up of lava which flows at the top. When the icecap melts, the

lava at the top collapse and form a flat-topped mountain. Examples of this type of

volcanoes are found in Iceland, Tuyas in British Columbia.

(iv) Mud Volcanoes:- Also called mud domes are formations created by geo-excreted

liquids and gases, although there are several processes which may cause such activity.

The largest structures are kilometers in diameter and height about 700 meters.

Composition of Lava:- The composition of lava is the factor to decide the type of

volcano. There are four different compositions.

(i) Felsic:- If the erupted magma contains 60% and more silica, it is called felsic.

Lassen Peak in California is of felsic lava. Sometimes there is pyroclastic flows which

are more dangerous.

(ii) Intermediate:- If the erupted magma contains 50 to 60% silica, they are said to be

intermediate. Lava of Mount in Merapi in Indonesia is of intermediate type.

(iii) Mafic:- When the erupted magma contains between 45 to 50% silica, it is called

mafic. It contains large quantities of iron and magnesium.

(iv) Ultramafic lava:- When the erupted magma contains less than 45% silica, it is

ultramafic lava.

Classification of Volcanoes:-

There are three classifications: (i) Active, (ii) Extinct and (iii) Dormant.

(i) Active:- Active volcanoes are those which erupt regularly. The word, ‘regularly’ is a

relative term. The life span may vary from months to years. Presently there are about

500 active volcanoes in the world many of them situated along the Pacific “Ring of Fire”.

Among this 500, about 50 of them erupt each year. The US has about 50 active

volcanoes. An estimated 500 million people live near active volcanoes.

(ii) Extinct:- Those volcanoes which have not erupted in historical times is called

‘Extinct’. They are extinct because there is no supply of lava. Again the term, ‘Extinct’ is

relative. Due to the change in physical processes inside the earth, a volcano which is

thought to be extinct, can become active; only thing is that the present generation may

not live to witness the eruption. Examples of extinct volcanoes are: Many volcanoes in

the Hawaiian - Emperor Seamount chain in the Pacific Ocean, Hohentwiel, Shiprock

and the Zuidwal volcano in Netherlands, Edinburgh Castle in Scotland is famously

located atop an extinct volcano.

(ii) Dormant:- Those which have erupted in the past, but now quiet are called ‘dormant’

or ‘inactive’. There is no much difference between an extinct volcano and a dormant

one. It all depends on for how much long time a volcano is inactive. If it is dormant for

appreciably long time, then it is said to be extinct. If the time for which it is inactive is

short, then we may say it is dormant. Examples are Soufriere Hills volcano in the island

of Montserrat considered to be extinct became active in the year 1995.

Plate Tectonic Theory (Cause of Volcanoes):- 6.1Cause of volcanoes can be

explained on the basis of Plate Tectonic Theory which is a generally acceptable by

geologists and specially volcanologists. According to this theory, the surface of the earth

is broken into a number of shifting slabs or plates which average about 50 miles in

thickness. These plates move relative to each other above a hotter, deeper, more

mobile zone at an average rate of few inches per year. Most of the world’s active

volcanoes are located along or near the boundary between shifting plates and are

called “Plate boundary volcanoes”. In the plate tectonics, there are two aspects. (i)

Divergent plate boundary and (ii) Convergent plate boundary.

(i) Divergent plate boundary:- Two tectonic plates diverge from one another at the

mid-oceanic ridges. Due to the cooling and solidifying of the molten rock, new oceanic

crust is formed. Due to the pull exerted by the tectonic plates, the crust becomes very

thin at the mid-oceanic ridges. The thinning of crust creates a pressure leading to an

adiabatic expansion and partial melting of the mantle thus causing ‘volcanism’. Most

divergent boundaries lie at the bottom of the ocean and hence most volcanic activity is

submarine, forming new sea floor. This is certainly a great boon by almighty by freeing

humans of the danger from many volcanoes. Black smokers or deep sea vents are

examples of this kind of volcanic activity. When the mid-oceanic ridge is above sea

level, volcanic islands are formed, for example, Iceland is a volcanic island.

(ii) Convergent Plate boundaries:- When an oceanic plate and a continental plate

collide, subduction zones are formed. That is the oceanic plate subducts or submerges

under the continental plate forming a deep ocean trench just offshore. The melting

temperature of mantle wedge decreased due to water released from the subducting

plate thus creating magma which is highly viscous because of the silica content. Many

times it is cooled at depth, but when it reaches the surface, a volcano is formed.

Example of such a volcano is the Mount Etna and all the volcanoes in the Pacific Ring

of Fire.

In the following Fig.6.46.5 is shown Plate tectonics, Convergent and Divergent

boundaries.

Fig. 6.4 Plate Tectonics (Credit: 6.5) Hot Spots:- There are some volcanic provinces postulated to be formed by mantle

plumes. They are called “Hot Spots”. Large columns of hot material rise from the core-

mantle boundary. As the tectonic plates move across them, each volcano becomes

dormant after a while and a new volcano is formed as the plate gets further shifted. The

Hawaiian islands have been formed in this manner and also the Snake River Plain with

the Yellowstone Caldera being the part of North American Plate currently above the Hot

Spot.

Types of Volcanic Eruptions:- Each volcano is different from the other one from the

point of view of the type of eruption. Each one shows a distinctive pattern of behavior.

Some erupts mildly simply discharge steam and other gases whereas others extrude

molten lava. The most spectacular one consists of violent explosion that blast great

clouds of gas-laden debris into the air. Any volcano erupting anywhere is compared with

the one already taken place elsewhere and the names are given accordingly. For

example, “Strombolian”, “Vulcanian”, “Vesuvian”, “Pelean”, “Hawaiian”, etc. The most

powerful eruption is called “Plinian” and is really a dangerous one because of the

pyroclastic flows from the vent.

Volcano Monitoring:- Volcano monitoring involves the following:

(i) Keeping a diary of changes taking in the volcano and also in the surroundings.

(ii) Searching for and observing ground cracks, if any.

(iii) Observing plant life.

(iv) Make temperature measurements of lava and gas.

(v) Collect the eruptive products for research.

(vi) Study by special instruments some phenomenon not visible to the human eye.

(vii) Record any ground movements, if any such as earthquake tremor taking place with

the help of precise seismic network.

(viii) Recording of changes in terrestrial magnetism during eruption.

(ix) Thorough chemical analysis of products of eruption.

(x) Measurement of changes in atmospheric temperature, humidity, etc. in the

neighborhood of volcano in action.

Damages from volcanoes and protection from it:- 6.8An article from the internet

published in March 2007 has extensively dealt with damages and protection from

volcanoes. The protection will depend upon the type of damage created by volcanoes.

Let us first deal with the damages.

Damages:- When volcanoes erupt, the possibilities are that high speed avalanches of

hot ash and rock with pyroclastic flows, lava and landslides can devastate areas 15

kilometers or more away, and huge mudflows of volcanic mud and debris can inundate

stream valleys at speeds of 30 to 60 kilometers per hour and can travel about 80 km

downstream.

Volcanic ash can affect people and equipment many kilometers away from a

volcano. Inhaling volcanic ash can create many respiratory problems. Explosive

eruption columns pose a serious threat to civil aviation as the ash from the explosion

can reach to a height of about 20 kilometers in less than half an hour. As the

temperature of erupting lava is between 500 to 1000°C and the flow destroys everything

in its path sometimes causing dangerous fires. The eruption is sometimes accompanied

by mild earthquakes or tremors. The other hazards are mudflows, flash floods, rock falls

and landslides, wild land fires and sometimes tsunamis.

Protection from Volcanoes:- This is enumerated in the following:

(i) One should know the volcano nearby, i.e. from its past history.

(ii) Try to understand and follow the government’s warning system through radio or

television.

(iii) Prepare for an evacuation plan and do not go by ‘hear-say’ from people not knowing

anything.

(iv) Keep handy a pair of goggles and dust mask for each member of your family to

protect from volcanic ash.

(v) Follow mudflow and landslide safety measures as instructed by the authorities.

(vi) When you are indoors, keep the windows, doors and dampers closed so as to avoid

the volcanic ash entering the house.

(vii) Keep all the household items, machinery or any other items duly covered with tarps.

(viii) If you are outdoors, take shelter indoors.

(ix) Running away is not a solution as the volcanic ash can travel many kilometers from

the volcano. Find some house and be inside.

(x) Avoid low-lying areas such as river valleys as the volcanic ash can settle in such

places by gravity action.

(xi) Wear a dust mask, goggles and try to cover your entire body.

(xii) Bring your domestic animals and cattle to closed shelters.

(xiii) So be prepared and remember the saying: “Do not dig well when the house is on

Fire”

What is to be done after an eruption?

(i) The volcanic ash and fine glassy particles remain in air for few days after the

eruption. Hence, wear goggles and keep your body covered till further instructions from

authorities.

(ii) Remove ash and volcanic dust from the roofs of your house.

(iii) Avoid driving for few days.

(iv) Clean your domestic animals and cattle. Give them a good wash.

Fig.6.5 (Credit: 6.3) a, b, c, d, e, f, g, h, i, j and k give pictures of volcanoes and other

related topics. In Fig. 6.66.4 is shown a Fissure Volcano.

Fig. 6.5 (a) Cleveland Volcano in the

Aleutian Islands of Alaska

photog raphed from the International

Space Station, May 2006

Fig. 6.5 (c) Lakagigar fissure vent in

Iceland, source of the major world

climate alteration of 1783

Fig. 6.5 (e) Pahoehoe Lava flow on

Fig. 6.5 (a) Cleveland Volcano in the

Aleutian Islands of Alaska

raphed from the International

Space Station, May 2006

Fig. 6.5 (b) Ash plumes reaching a

height of 19 km during the climactic

eruption of Mount Pinatubo, Philippines

in 1991

Fig. 6.5 (c) Lakagigar fissure vent in

Iceland, source of the major world

climate alteration of 1783 -84.

Fig. 6.5 (d) Skjaldbreiour, a shield

volcano whose name means “broad

shield”.

Fig. 6.5 (e) Pahoehoe Lava flow on Fig. 6.5 (f) The Stromboii stratovolcano

Fig. 6.5 (b) Ash plumes reaching a

height of 19 km during the climactic

eruption of Mount Pinatubo, Philippines

in 1991

Fig. 6.5 (d) Skjaldbreiour, a shield

volcano whose name means “broad

shield”.

Fig. 6.5 (f) The Stromboii stratovolcano

Hawaii. The picture shows overflows of

a main Lava channel.

Fig. 6.5 (g) Sarychev Peak eruption, Matua

Island, oblique satellite view.

Fig. 6.5 (i) Fresco with Mount Vesuvius

behind Bacchus and Agathodaimon as

seen in Pompeii’s House of the Centenary.

Hawaii. The picture shows overflows of

a main Lava channel.

off t he coast of Sicily has erupted

continuously for thousands of years,

giving rise to the term, “Strombolian

Eruption”.

Fig. 6.5 (g) Sarychev Peak eruption, Matua

Island, oblique satellite view.

Fig. 6.5 (h) Four- peaked volcano, Alaska in

September 2007 after being thought extinct

for over 10,000 years.

Fig. 6.5 (i) Fresco with Mount Vesuvius

behind Bacchus and Agathodaimon as

seen in Pompeii’s House of the Centenary.

Fig. 6.5 (j) Koryaksky volcano towering

over Petropavlovsk- Kamchatka Peninsula,

Far Eastern Russia.

he coast of Sicily has erupted

continuously for thousands of years,

giving rise to the term, “Strombolian

Eruption”.

peaked volcano, Alaska in

after being thought extinct

for over 10,000 years.

Fig. 6.5 (j) Koryaksky volcano towering

Kamchatka Peninsula,

ar Eastern Russia.

Fig. 6.5 (k) Schematic of volcano injection

of aerosols and gases.

6.6Lindsay Martin has stressed the importance of monitoring volcanoes in the

Eastern Sierra Nevada because

According to him, future eruptions can be predicted by comparing the previous data

already obtained with the one obtained from the measurements of gas emissions,

detecting crustal deformation, measuring sei

systems. The Eastern Sierra Nevada has a long history of volcanic eruption right from

28 million years ago. The area from Los Angeles to Nebraska will be affected as shown

in Fig. 6.7. The volcano, even though dorman

Records show that the

Eastern Sierra Nevada has been

quiet for the last 250 years, but

the caldera found in 1980

showed the possibility of

eruption any time. Four

earthquakes (M6) and the

subsequent tremors resulted

the elevation of the resurgent

dome by about 10 inches.

Fig. 6.7 Geological map of Long Valley and Mono Lake

Fig. 6.5 (k) Schematic of volcano injection

of aerosols and gases.

Fig. 6.6 A Fissure Volcano There is no

central crater. Lava spreads far and Wide

and when cooled, gets solidified and the

Surface remains flat. There is nothing to

look like a volcano.

Lindsay Martin has stressed the importance of monitoring volcanoes in the

Eastern Sierra Nevada because of the continuous fear of volcanoes in that area.



detecting crustal deformation, measuring seismic activity and studying hydrothermal



in Fig. 6.7. The volcano, even though dormant for 50,000 years, it is not extinct.

Records show that the

Eastern Sierra Nevada has been

quiet for the last 250 years, but

the caldera found in 1980

showed the possibility of

eruption any time. Four

earthquakes (M6) and the

subsequent tremors resulted in

the elevation of the resurgent

dome by about 10 inches.

Fissure Volcano

Fig. 6.7 Geological map of Long Valley and

Fig. 6.6 A Fissure Volcano There is no

central crater. Lava spreads far and Wide

gets solidified and the

Surface remains flat. There is nothing to

look like a volcano.

Lindsay Martin has stressed the importance of monitoring volcanoes in the

of the continuous fear of volcanoes in that area.



smic activity and studying hydrothermal



t for 50,000 years, it is not extinct.

Lava flows

Fissure Volcano

Fig. 6.8 Principle of InSAR

Another earthquake in 1997 created a four inch increase of the resurgent dome. Various

methods used by the author to monitor volcanoes in this region are: (i) Study of Crustal

Deformation, (ii) Seismi-city, (iii) Gas Emissions and (iv) Hydro thermal Activity.

(i) Study of Crustal Deformation:- As the Long Valley area is near the Basin and

Range Province and the San Andreas Fault, frequent earthquakes Fig. 6.7 Geological

map of Long Valley and Mono Lake deform the earth’s crust. The crustal deformation

can be measured by means of Global Positioning System (GPS), Leveling, a special

type of radar known as Interferometric Synthetic Aperture Radar (InSAR) and tiltmeters.

The crustal deformation can be best studied by Global Positioning System. The

system uses satellites in space and if there is some error in the measurement, a

Differential Global Positioning System (DGPS) is used. The ground tilt can be measured

by tilt meters. Crustal deformation can be measured by leveling also.

InSAR is a remote sensing

technique illustrated in Fig. 6.8. Two

Radar images are taken at two different

times. Radio waves are bounced off the

surface on two different passes. Phase

difference resolve elevation changes in

fraction of wavelength. Crustal

deformation can be detected from the

difference in the images. InSAR is an

advantageous method and surveyors like it as it can be operated in hazardous areas

also.

(ii) Seismicity:- Measuring seismic activity near a volcano is very important as it can

record tectonic movements. Tremors usually occur near a volcano in action. Precise

seismometers about 6 in number should be kept within a radius of 20 kilometers.

(iii) Gas Emissions:- The gas associated with the magma enters the ground through

cracks. It should be collected and chemically analysed.

(iv) Hydrothermal Activity:- It is observed that in the Eastern Sierra Nevada there is

hydrothermal activity because of the presence of magma below the surface. Fumaroles

and hot springs are the indications. The volcanic unrest can be indicated by the

changes in hydrothermal activity. Certain chemical concentrations in water such as

Fig. 6.9 Graph of thermal water input to hot

creek

chloride and hydrogen sulphide and temperature are measured in hydrothermally active

regions.

In Fig. 6.9 is shown a

thermal water input to Hot

Creek. The United States

Geological Survey (USGS)

monitors the thermal water

discharge in Hot Creek gorge by

measuring chloride

concentration in the stream

above and below the hot

springs. The onset of

geysering in 2006 was

accompanied by a small spike in

discharge. Temperature changes are common in the Hot Creek in the Long Valley

Caldera.

Analysis of Data:- The Long Valley Observatory along with other agencies analyze the

data and compare the same with the data from the previous eruptions. It is found that

the resurgent dome is rising by one inch a year and has so far risen by 80 cm since

1978. Researchers have detected that there is a shallow intrusion of magma

underneath the resurgent dome and a deeper intrusion beneath the South Moat of the

Caldera as illustrated in Fig. 6.10.

Prediction is very important from the point of view of safety of the population. The

extreme heat from the Hot Creek has killed many. The emission of carbon dioxide is

equally dangerous. The United States Geological Survey has already charted programs

for prediction.

The prediction arrived at is as follows: The next eruption whenever it happens will be

similar to the ones of the Mono-lnyo chain. These eruptions are similar but explosive.

First as usual there will be a phreatic phase and the steam throws debris in the air

creating a crater. Next, magma can reach the surface of the vent and the gases trapped

in the magma are dissolved out of solution creating an explosive eruption. There will be

ash fall and pyroclastic flow and destroy anything on its way. If the eruption happens in

the winter, there will be mud flow and severe flooding.

Fig. 6.10 Epicenters of earthquakes of magnitude gr eater than 3 in the Long

Valley Caldera Circle sizes indicate the magnitude of the earthquake

6 7Steven N. Ward and Simon Day in their research paper titled,

Volcano -Potential collapse and tsunami

of an on-coming tsunami. They assert that according to geological evidence, in a future

eruption, the volcano on this island might drop 150 to 500 cubic kilo

the sea and have mathematically predicted a tsunami as an after

waves acquiring speeds of 100 m/s

arrive at the coast of the Americas with 25 m height.

The residual debris found on the sea floor indicates a lateral collapse of oceanic

island volcanoes with magnitude (up to 5000 km

length and ferocity 140 m/s

possibility because of the number of active oceanic islands in which few of them show

signs of instability. The authors in this paper have discussed the possibility of a ts



Steven N. Ward and Simon Day in their research paper titled,

Potential collapse and tsunami at La Palma, Canary Islands”

coming tsunami. They assert that according to geological evidence, in a future

eruption, the volcano on this island might drop 150 to 500 cubic kilo

the sea and have mathematically predicted a tsunami as an after-effect of eruption with

waves acquiring speeds of 100 m/s. This could transit the entire Atlantic Basin and can

arrive at the coast of the Americas with 25 m height.

esidual debris found on the sea floor indicates a lateral collapse of oceanic

island volcanoes with magnitude (up to 5000 km3 of material) extending to 300 km of

length and ferocity 140 m/s inside water. The onset of tsunami in the Atlantic is a

y because of the number of active oceanic islands in which few of them show

signs of instability. The authors in this paper have discussed the possibility of a ts



Steven N. Ward and Simon Day in their research paper titled, “Cumbre Vieja

La Palma, Canary Islands” sites a warning

coming tsunami. They assert that according to geological evidence, in a future

eruption, the volcano on this island might drop 150 to 500 cubic kilometres of rock into

effect of eruption with

This could transit the entire Atlantic Basin and can

esidual debris found on the sea floor indicates a lateral collapse of oceanic

of material) extending to 300 km of

inside water. The onset of tsunami in the Atlantic is a

y because of the number of active oceanic islands in which few of them show

signs of instability. The authors in this paper have discussed the possibility of a tsunami

created from the instability of one of the volcanoes, Cumbre Vieja on the island of La

Palma, Canary islands (Fig. 6.11). As evidenced by the abundant landslide deposits

strewn about their bases, the Canary island volcanoes have experienced about a dozen

collapses in the past several years.

The location details showing the geological deposit

6.12. It is found that the distribution and orientation of vents and feeder dykes within the

mountain have

Fig. 6.11 (inset) Canary island chain off

the Western coast of Africa. Above:

Location of La Palma island where the

volcano is Situated.

Have shifted from a triple rift system to one consisting of a single N

westward extending arrays. The recent eruption of this volcano in 1949 has indicated a

normal fault along the crest of the volcano (Fig. 6.12) in support of volcano’s eruptive

phase. The 1949 fault break skirts the crest of the volcano about 8 km inland and marks

the eastern boundary of the unstable zone. The authors say that there is the best

geological evidence of a collapse of Cumbr

and 15-25 km long and they believe that a future flank failure of Cumbre Vieja volcano

will dislodge a broadly wedge

6.12. Some of the remains of the previous collapse can be seen at the site of the

volcano.

6.9Prof. Gifford Miller of the University of Colorado, US published a news item from

Washington in the Free Press Journal, Mumbai dated 1 February 2012, titled

ity of one of the volcanoes, Cumbre Vieja on the island of La

alma, Canary islands (Fig. 6.11). As evidenced by the abundant landslide deposits


collapses in the past several years.

The location details showing the geological deposits in the island is shown in Fig.


Fig. 6.11 (inset) Canary island chain off

the Western coast of Africa. Above:

Location of La Palma island where the

volcano is Situated. (Credit: 6.7)

Fig. 6.12 Map of La Palma Island

showing the major geological

deposits,

om a triple rift system to one consisting of a single N



949 fault break skirts the crest of the volcano about 8 km inland and marks


geological evidence of a collapse of Cumbre Vieja down a side block 15

long and they believe that a future flank failure of Cumbre Vieja volcano

will dislodge a broadly wedge-shaped slide block as cartooned at the bottom of Fig.


f. Gifford Miller of the University of Colorado, US published a news item from


ity of one of the volcanoes, Cumbre Vieja on the island of La

alma, Canary islands (Fig. 6.11). As evidenced by the abundant landslide deposits


s in the island is shown in Fig.


Fig. 6.12 Map of La Palma Island

showing the major geological

deposits, (Credit: 6.7)

om a triple rift system to one consisting of a single N-S rift with



949 fault break skirts the crest of the volcano about 8 km inland and marks


eja down a side block 15-20 km wide

long and they believe that a future flank failure of Cumbre Vieja volcano

shaped slide block as cartooned at the bottom of Fig.


f. Gifford Miller of the University of Colorado, US published a news item from


Fig. 6.13 Eruption of Popocatepetl volcano

“Volcanoes may have initiated ‘Little Ice Age’ in t he 13th Century” and the same is

reproduced below in italics:

“A period of cooling temperatures that lasted till the late 19th century referred as

“Little Ice Age” was triggered by a series of volcanic eruptions and sustained by sea ice,

a new study has suggested. During that cool spell, advancing glaciers destroyed many

European towns and froze the Thames River in London and canals in the Nether Lands,

the places that are now ice free. There is also evidence it affected other continents.

The new study, which looked at chemical clues preserved in arctic vegetation as well

as other data, also pinpointed the start of the cool spell to the end of the 13th century.

This is the first time anyone has clearly identified the specific onset of the cold times

making the start of the “Little Ice Age” lead study author, Prof. Gifford Miller of the

University of Colorado, USA, was quoted as saying by LiveScience.

The cause, according to the researchers, appears to have been massive tropical

volcanic eruptions, which spewed tiny particles called aerosols into the atmosphere.

While suspended in the air, the aerosols reflect solar radiation back into space, cooling

the planet below, they said.

The researchers came to these conclusions by looking at radiocarbon dates based

on how much of the radioactive form of carbon they contain from dead plants revealed

by melting ice on Baffin Island in the Canadian Arctic.

Their analysis found that many plants at both high and low altitudes died between

1275 AD and 1300 AD evidence that Baffin Island froze over suddenly.

These periods coincide with two of the most volcanically active period in the past

millennium, according to the researchers.

They also found that the annual layers in sediment cores from a glacial lake linked

with an icecap in Iceland suddenly became thicker, indicating increased erosion caused

by the expansion of the icecap in the late 13th century and in the 15th century.

Simulations using a climate model showed that several large, closely spaced

eruptions could have cooled the northern hemisphere enough to spark sea-ice growth

and the subsequent feedback

loop, the researchers said.” 6.10As this part of the thesis

being written, there is a news

item dated today (Friday, 20 April in 2012) in the Free Press Journal, Mumbai with A

picture (Fig. 6.13) of Popocatepetl Volcano getting erupted in San Andres Cholula,

Mexico. Birds are seen flying in the foreground as a plume of ash and steam rise from

the volcano.

Conclusion:- As I mentioned in the introduction that volcano is a good friend, but a bad

master.

It creates havoc and harass people, but the volcanic products contain many useful

minerals. They break down to form some of the most fertile soils on Earth and used by

many civilizations. The volcanic products are used in the construction industry. The

products have many chemical and industrial uses. One can tap geothermal energy from

volcanoes as used in the northern California, US to meet the power requirements of city

of San Francisco.

A short term mitigation during eruption, but a long term benefit of volcanism. Volcano

is certainly a great wonder from the interior of the Earth.

One observation and finding from the study of volcanoes specially the topic related

to protection is that as one cannot prevent eruption of volcanoes, the eruption goes on

and one should try to live with it and it is a fact like how the Japanese live with

earthquakes and tsunamis, in the same way, people in volcanic regions live with it, of

course by taking precautions. Avoid population in and around a volcano. As the volcanic

ash and emitted gases travel great distances due to blow of winds, something should be

done for our breathing. A quarter century before when the Bhopal gas tragedy took

place killing thousands of people, the deaths were mainly due to inhalation of poisonous

gases. Somebody suggested and that appeared in the press saying that simple plain

natural water can create a miracle. Water is a universal solvent and a good absorber of

some, if not all, chemicals. Its large specific heat can absorb heat as well. Hence, a

special spongy dress soaked in water covering even the head and of course, a pair of

goggles is a must, can protect the person near a volcanic region during eruption. At

least the number of deaths can be decreased. Some chemists may not agree with my

suggestion. It is left to the readers of this thesis for further suggestion.

REFERENCES :

[1] 6.2Carnegie Library of Pittsburgh, “The Handy Science Answer Book”, ISBN: 1-

57859-140-6, Ed.2005, p.105-6.

[2] 6.9Free Press Journal, Mumbai dated 1 Feb. 2012,”Volcanoes may have initiated

‘Little Ice Age’ in 13th century”.

[3] 6.5John Langone, Bruce Stutz and Andrea Gianopoulos; “The Theories of

Everything” from National Geographic, ISBN: 978-1-4351-3339-6, p.337. Ed.

2011.

[4] 6.6Martin Lindsay, “Monitoring Volcanoes in the Eastern Sierra Nevada. The

Methods and Their Use for Predicting Future Eruptions”, June 2010, p.1-13.

[5] 6.10Miller Gifford, Prof. Uni. Of Colorado, US, “Volcanoes may have initiated ‘Little

Ice Age’ in 13th century”, a news item published in the Free Press Journal, Mumbai

dated 1 Feb. 2012.

[6] 6.4South Carolina Geological Survey Educational Series #9, “Types of Volcanoes”.

[7] 6.1Tilling Robert I; “Volcanoes”, 1991 (year obtained from ref.)

[8] 6.8“Volcanoes”, an article from net published in March 2007.

[9] 6.3“Volcano”, Wikipedia Encyclopedia, 2010 (latest from ref.).

[10] 6.7Ward Steven N and Simon Day, “Cumbre Vieja Volcano - Potential collapse and

tsunami at La Palma, Canary Islands”, 27 Jun 2001, p.1-5.

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