All about VOLCANOES

1by Tarun Goyal

A Volcano is an opening in the earth’s crust

through which gases, molten rock material,

ash, steam etc. are emitted outward in the

course of an eruption.

Such vents or openings occur in those parts of

the earth’s Crust where the rock strata are

relatively weak.

Depending upon the explosive nature of the

volcano, different landforms can be formed

such as a plateau / plain (if the volcano is not

explosive) or a mountain (if the volcano is

explosive in nature).

Magma is used to denote the molten rocks and

related materials seen inside earth. A weaker

zone of the mantle called Asthenosphere,

usually is the source of magma.

Once this magma comes out to the earth

surface through the vent of a volcano, it is

called as the Lava. Therefore, lava is nothing

but the magma on earth surface. 2

Causes of Volcanic Eruptions

Our Earth hasn’t cooled from inside. Some amount of heat which

was captured at the centre of the earth during its formation is stillpresent.

Besides, in the interior of the earth, the radioactive substances

undergo chemical reactions which generate a large amount ofheat.

This leads to a creation of large temperature difference betweenthe inner and outer layers of earth.

This leads to the formation of convection currents in the Mantle.

Due to this, the molten magma along with the gaseous materialscomes out to the earth’s surface at the first available opportunity.

This mainly occurs in the weak zones of earth surface such asDivergent and Convergent Plate Boundaries.

3

Basic lava is non-viscous, is darker in colour and has lower silica content. As

basic lava is non-viscous, it can reach very far from the vent before it finally cools

down and solidifies. Therefore, its cones have short height, concave slopes and

large base area. It is also known as mafic lava due to low silica content.

Note : Pyroclasts is fluidized mixture of solid to semi-solid fragments and hot,expanding gases that flows down the flank of a Volcanic Vent. These are heavier-than-air emulsions that move much like a snow avalanche, except that they arefiercely hot, contain toxic gases, and move at phenomenal, hurricane-force speeds,often over 100 km/hour.

Tephra are rock fragments and particles ejected by a volcanic eruption (regardless ofcomposition, fragment size, etc.). 4

TYPES OF LAVA

Based on chemical composition, lava may be acidic or basic.

Acidic lava is viscous, lighter in colour and has higher silica

content. As the lava is thick and viscous, it is slow-flowing and

solidifies quickly near the vent. This produces a cone with steep

slopes. This kind of volcanoes usually erupts violently. Example : Mt

Stromboli in Italy is an acidic lava volcano. It is also known as felsic

lava due to high silica content.

A Volcanic Bomb is a mass

of molten rock (tephra) larger

than 2.5 inches (64 mm) in

diameter, formed when a

volcano ejects viscous

fragments of lava during an

eruption. Smaller tephra are

called lapilli.

They cool into solid

fragments before they reach

the ground. Because volcanic

bombs cool after they leave

the volcano, they are

extrusive igneous rocks.

Volcanic bombs can be

thrown many km from an

erupting vent, and often

acquire aerodynamic shapes

during their flight.

Pumice is a highly vesicular rough textured light colored volcanic

rock (an igneous rock). It is so light weight that it can float on water.

Pumice is created when super-heated, highly pressurized rock is

violently ejected from a volcano. The unusual foamy configuration of

pumice happens because of simultaneous rapid cooling and rapid

depressurization.

The depressurization creates bubbles by lowering the solubility of

gases (including water and CO2) that are dissolved in the lava,

causing the gases to rapidly exsolve (like the bubbles of CO2 that

appear when a carbonated drink is opened). The simultaneous

cooling and depressurization freezes the bubbles in a matrix.

Eruptions under water are rapidly cooled and the large volume of

pumice created can be a shipping hazard for cargo ships.

Scoria is another vesicular volcanic rock that differs from pumice in

having larger vesicles, thicker vesicle walls and being dark colored

and denser.

Cinders are extrusive igneous rocks; they are fragments of solidified

lava. Cinders are typically brown, black, or red depending on

chemical composition and weathering. Cinders are similar to pumice.

6

Pumice

Scoria

Cinders

Volcanic Bomb

VOLCANIC FEATURES

The Vent is the central passageway through which

magma passes.

The Crater is the central depression above the vent

from which the lava is thrown out.

A volcanic eruption may create cracks in the volcano.

Lava may rise through these cracks to cause a small

eruption. This forms a small volcanic cone called a

Parasitic Cone on the side of the principal one.

When the crater of a volcano is filled with water, a

Crater Lake is formed.

Calderas are large, circular, basin-shaped hollows on

the top of a volcano, & are formed when a very violent

eruption blows off the upper part of the volcano.7

CLASSIFICATION OF VOLCANOES

Volcanoes are classified under different schemes:

1. Classification on the basis of Periodicity of Eruptions:

A. Active Volcano: Volcano that has had at least one eruption during the past 10,000

years.

There are about 1,500 potentially active volcanoes worldwide, aside from the continuous

belts of volcanoes on ocean floor at spreading centers like the Mid-Atlantic Ridge. 75% of

those are located along the Pacific Ring of Fire.

8

Volcanoes in Decreasing Order of Vulcanicity

1. Mt. Kilaeau (most active volcano in the world) in Hawaii, 2. Etna in Sicily, 3.

Piton de la Fournaise on Réunion Island, 4. Merapi in Indonesia, 5. Erta Ale

in Ethiopia, 6. Ol doinyo lengai in Tanzania, 7. Mount Unzen in Japan, 8.

Mount Yasur in Vanuatu, 9. Santa Maria in Guatemala, 10. Sakurajima in

Japan, 11. Galeras in Columbia, 12. Taal in Philippines, 13. Mt Nyiragongo in

DRC, 14. Vesuvius in Italy, 15. Eyjafjallajokull in Iceland.

Others are Mauna Loa in Hawaii, Stromboli in Mediterranean Sea (called

Lighthouse of the Mediterranean Sea), Fujiyama in Japan, Krakatoa in

Indonesia, Barren Island Volcano in Andamans, etc.

B. Dormant Volcano: Volcano which has been quiescent for a long

time but in which there is a possibility of eruption. E.g., Narcondam

Island volcano of Andaman and Nicobar islands, Mt. Kilimanjaro

(Tanzania), Mt. Fuji (Japan).

Volcanoes become dormant because the Earth’s plates are

constantly shifting above volcanic hotspots.

Each time the hotspot reaches the surface, it creates a new volcano.

The tectonic plate continues to shift above the hotspot, and

eventually the volcano is shut off from the magma chamber beneath.

E.g., Mauna Kea in Hawaii.

C. Extinct Volcanoes are those where the volcanic eruption had

taken place in historic times but they are not active today.

Mt Chimborazo in Ecuador, Mt Kenya in Eastern Africa, and Mt Popa

in Myanmar etc. are the examples of extinct volcanoes. 9

2. Classification on the basis of Nature of Eruption and the Form developed at the

surface :

Fissure Eruption or Quiet Eruption Type

Large quantities of lava quietly flow up from fissures and spread out over the

surrounding areas. On account of the absence of explosion, pyroclastic material is

absent.

Fissure eruptions do not build large volcanic cones but more commonly they build

lava plateaus and plains.

In fissure eruption, there is no pipe leading directly to the magma in the earth's

interior but there is a long fissure and the eruption may be either along the entire

fissure or at selected points along the fissure.

An excellent example is the Deccan Lava plateau of India. The region is commonly

referred to as the Deccan trap as the successive lava flows with their different

thicknesses have resulted in step-like structure.11

12

Shield Volcanoes

They are the largest of all volcanoes in the world as the lava flows to a far distance. Example :

Hawaiian volcanoes.

They are not very steep but are far and wider. They extend to great height as well as distance.

If you were to fly over top of a shield volcano, it would resemble a warrior’s shield, hence the name.

These volcanoes are mostly made up of basalt (less viscous). For this reason, these volcanoes arenot steep.

They are not explosive in general, but if somehow water gets into the vent they may turn explosive.

The upcoming lava moves in the form of a fountain & throws out the cone at the top of the vent anddevelops into cinder cone. Most cinder cones have a bowl-shaped crater at the summit.

13

14

Composite or Strato Volcanoes

Volcanologists call these “strato-” or composite volcanoes because they consist of layers of solid

lava flows mixed with layers of sand- or gravel-like volcanic rock called cinders or volcanic ash.

They are characterized by the eruption of more viscous lavas than basalt.

These volcanoes often result in explosive eruptions.

Along with lava, large quantities of pyroclastic materials and ash find their way to the ground.

This material accumulates in the vicinity of the vent openings, leading to the formation of layers,

and this makes the mount appears as composite volcanoes.

Mayon Volcano in the Philippines, Mount Fuji in Japan, and Mount Rainier in Washington are the

major composite volcanoes in the world.

15

Caldera

These are the most explosive of the earth’s volcanoes.

They are usually so explosive that when they erupt they tend to collapse on themselves

rather than building any tall structure. The collapsed depressions are called calderas.

Their explosiveness indicates that its magma chamber is large and in close vicinity.

A caldera differs from a crater in such a way that a caldera is a huge depression caused by

a collapse after a large-scale eruption, whereas a crater is a small, steep side, volcanic

depression bored out by an eruptive plume.

Even lakes can be formed in calderas (Caldera Lakes). E.g. : Ojos del Salado Lake

(highest crater lake), Lake Toba (Indonesia; largest crater lake).

16

17

Laguna de Quiltoa, a caldera in Ecuador

Maar

It is a shallow volcanic crater with steep sides

that is surrounded by tephra deposits.

The tephra deposits are thickest near the

crater and decrease with distance from the

crater.

A maar is formed by one or more underground

explosions that occur when hot magma comes

into contact with shallow groundwater to

produce a violent steam explosion. These

explosions crush the overlying rocks and

launch them into the air along with steam,

water, ash and magmatic material.

The materials usually travel straight up into air

& fall back to Earth to form the tephra deposits

that surround the crater. If the tephra lithifies, it

will become an igneous rock known as tuff. 18

Phreatic Eruption

The explosions that form a maar are known as phreatic explosions.

It occurs when magma heats groundwater or surface water. The

extreme temperature of the magma (anywhere from 500°C to

1,170°C) causes near-instantaneous evaporation of water to steam,

resulting in an explosion of steam, water, ash, rock and volcanic

bombs.

Note : When suddenly heated, one cubic meter of water converts into

1,600 cubic meters of steam. If this happens below Earth's surface, the

result can be a vertical eruption of steam, water, ash, volcanic bombs,

and rock debris.

Eg : At Mount St. Helens in Washington state, hundreds of steam

explosions preceded a 1980 Plinian eruption of the volcano.

A scheme of a Phreatic

Eruption :

1: water-vapour cloud,

2: magma conduit,

3: layers of lava and ash,

4: stratum,

5: water table,

6: explosion,

7: magma chamber

TYPES OF VOLCANIC ERUPTION

I. Central Eruption

In this, the eruption takes place through a central vent or mouth.

The rock fragments, ash, lapilli (material that falls out of the air

during a volcanic eruption) as well as liquid lava are ejected with

more or less explosion & collect around the mouth.

In this type of eruption, the volcanic eruption is confined to a pipe-

like vent and after the eruption, cone and crater structure is

developed.

A good example of this type is the Cotopaxi volcano in Ecuador.

Sometimes, in addition to the main hole, there may be satellite

holes on the slope of the hill through which lava may escape at

lower elevations. Etna Volcano is an example.

II. Fissure Eruption : Already discussed

21

TYPES OF CENTRAL ERUPTIONS1. Hawaiian Type

• Volcanoes of this type show less explosive activity and the eruption is peaceful.

• In other words, Hawaiian activity is essentially effusive.

• The gases are not so powerful and lava is of thin basalt variety.

• Sometimes, fountains of basaltic spray rise up with the gases and when the wind is strong,

these lava pieces are stretched into long shiny threads known as Pele’s Hair (after Pele, the

Goddess of fire in these islands).

• This type of eruption is especially characteristic of the Hawaiian Islands and hence its name.

The basalt plateaus of the Columbia Plateau (Washington, Oregon & Idaho, in US) and

Iceland provide other examples of this type of eruption.

22

23

2. Strombolian Type

• In this type, the basaltic lava is not quite as thin as in the Hawaiian type, and the gases

come out either continuously or interruptedly with moderate explosive action.

• The explosion is relatively mild.

• Normally eruption is intermittent and fountains of lava are ejected at regular, rhythmic

intervals varying from a few minutes to about an hour, and flows are unusual.

• Neither in the Hawaiian nor in the Strombolian type of volcanoes do we find clouds of

black smoke.

• Stromboli is an island in the Lipari Group of Islands, in the Tyrrhenian Sea north of Sicily

in the Mediterranean Sea, where this type of eruption is found.

• The lava-fountain activity of Stromboli, reflected at night as a red glow on the downside

of a towering steam plume has caused the volcano to be known as the Lighthouse of the

Mediterranean.

24

3. Vulcanian Type

• Vulcanian activity is explosive, named after volcano of Vulcano, located in the Lipari Islands.

• In this, the lava is so thick and viscous that it is unable to remain in a liquid condition after

coming in contact with air & solidifies & seals the mouth of Crater in between two eruptions.

• This blocks the passage of the gases from inside, and after sometime when the gases have

collected in adequate quantities and their pressure is intense, they force through the solidified

vent with explosion.

• All sizes of fragmental materials are thrown out with predominance of volcanic ash and dust.

• Masses of black clouds filled with ash and dust rise to great heights and give the appearance

of huge cauliflowers from the distance.

• In the Krakatoa Island of Indonesia, the eruption in 1883 was of this type which was followed

by the Vesuvian Type.

25

4. Vesuvian or Plinian Type

• In this type of eruption, there is violent explosion due to the intensity of the gases and the lava

comes out with great force.

• Lava comes out first from the lateral cracks, but the gases keep on accumulating in the main Vent.

• When the pressure has eased a bit on the top, on account of the ejection of lava from the lateral

cracks, then under the influence of the intense gases, the lava comes out rapidly with the

explosion, the gases forming cauliflower-like clouds.

• These clouds rise to great heights and look very shining and bright and cause downpours of ash

over considerable distances.

• In the Krakatoa eruption of 1883, such clouds had risen to heights of nearly 80 km in the

atmosphere.

• Another example is the eruption of Mount Vesuvius in 79 CE, which destroyed the ancient Roman

cities of Herculaneum and Pompeii. It is named after Pliny the Younger (a lawyer, author, and

magistrate of Ancient Rome), who carefully described the disastrous eruption.

26

5. Pelean Type

• This type of volcanic eruption is violentlyexplosive and the lava is highly viscous.

• At the time of the eruption, the dense lava

solidifies and closes the mouth of the crater anda Dome is formed there.

• After some time, the powerful gases trapped

inside either breakthrough this obstacle or come

out along the hill slope, and then an exceedingly

dense mass of hot, highly gas charged lava

mixed with fragmental materials and ash, flowsdown the slope like an avalanche.

• These have been called ‘nuees ardentes’ or

glowing clouds.

• Pelean type explosion differs from the Vulcanian

in that the very hot gas and lava mixture is not

thrown upwards but spreads downslope asnuees ardentes.

• The nuees ardentes is extremely dense but

highly mobile on account of the gases and

moves rapidly down the hill slope almost withoutfriction.

• Nuees ardentes is the most terrifying form ofexplosive volcanic activity.

• It is, however, soundless as in spite of the fact

that it has the velocity of winds in a hurricane,

the glowing fragments in the nuees ardentes are

cushioned by hot gas and are not abraded by the

turbulent motion.

• In 1902, in Martinque Island of the West Indies,

there was terrific explosion of Mount Pelee and

the nuees ardentes completely destroyed the

town of Saint Pierre located at the bottom of thehill and all its inhabitants were killed.

27

Mid-Ocean Ridge

Volcanoes

These volcanoes

occur in the oceanic

areas.

There is a system of

mid-ocean ridges

more than 70,000 km

long that stretches

through all the ocean

basins.

The central portion of

this ridge experiences

frequent eruptions.

28

DISTRIBUTION OF VOLCANOES

About 15% of world’s active volcanoes are found along ‘constructive

or divergent’ plate margins, whereas 80% volcanoes are associated

with ‘destructive or convergent’ plate boundaries.

a. The Circum-Pacific belt or the ‘Ring of Fire’: It extends across

the Kamchatka Peninsula, Kurile Islands, the Islands of Japan,

Philippines, New Guinea, New Zealand and the Solomon Islands. It

also passes through the Antarctica and the western coast of

America.

b. The Mid-Continent belt : It includes volcanoes of Alpine mountain

chain, the Mediterranean Sea and the fault zone of eastern Africa.

E.g., Stromboli, Vesuvius, Etna, Kilimanjaro, etc.

c. The Mid-Atlantic belt in which the volcanoes are fissure eruption

type. E.g., Iceland, Canary Islands, Cape Verde, Azores, etc.29

30

INTRUSIVE VOLCANIC LANDFORMS

The solidification of the lava forms volcanic landforms either inside

the surface of the earth or outside its surface.

When the lava is not able to reach the surface of the earth it enters in

the fissures of the earth and depending on the shape of the fissure

and its position with respect to the surface of the earth different types

of intrusive landforms develop.

Major intrusive forms include Batholiths, Laccoliths, Lopolith,

Phacolith, Sills and Dykes.

ALREADY DISCUSSED

OTHER ASSOCIATED LANDFORMS

• Hot springs and geysers also are manifestations of volcanic activity. They result from

the interaction of groundwater with magma or with solidified but still-hot igneous rocks

at shallow depths.

• Groundwater percolates through porous rock into fractures deep underground, where

heat from a nearby magma chamber superheats the pressurized water to a

temperature above the boiling point of water at surface pressure.

• HOT SPRINGS are formed when superheated water flows onto the earth’s surface.

34

• GEYSERS are intermittent hot springs in which superheated water

and steam are ejected to the earth’s surface at regular intervals.

Example: Old Faithful Geyser in Yellowstone National Park in US

(erupts about every 65 minutes). Also, Strokkur in Iceland (erupts

every 6-10 minutes).

• FUMAROLES are vents that eject steam & gases from earth’s

crust.

• Solfataras are fumaroles that eject sulphur-rich gases.

Geysers are hot springs that intermittently spout a column of

hot water and steam into the air. This action is caused by the

water in deep conduits beneath a geyser approaching or

reaching the boiling point.

At 300 m below the surface, the boiling point of water increases

to approx. 230°C because of the increased pressure of the

overlying water. As bubbles of steam or dissolved gas begin to

form, rise, and expand, hot water spills from the geyser’s vent,

lowering the pressure on the water column below. Water at

depth then momentarily exceeds its boiling point and flashes

into steam, forcing additional water from the vent. This chain

reaction continues until the geyser exhausts its supply of boiling

water.

In hot springs, the rising superheated water is cooled below

the boiling point by groundwater before reaching the surface.

35

36

• Geysers, fumaroles and hot springs are generally found in regions of young

volcanic activity. Surface water percolates downward through rocks below

Earth's surface to high-temperature regions surrounding a magma reservoir,

either active or recently solidified but still hot.

• There the water is heated, becomes less dense, and rises back to the surface

along fissures and cracks.

• Sometimes, these features are called "dying volcanoes" because they seem to

represent the last stage of volcanic activity as the magma, at depth, cools and

hardens.

• These can be utilized to produce Geothermal Energy. Major geothermal fields

are situated in Circum-Pacific margins, Rift zones of East Africa, North Africa,

Mediterranean basin, across Asia to Pacific.

• With an installed capacity of 3,639 MW in 2018, the US is the leading producer

of geothermal energy across the world, producing 16.7 billion kilowatt hours

(kWh) of geothermal energy throughout the year. Then comes Indonesia,

Philippines, Turkey, New Zealand, Mexico, Italy and Iceland.

• There are 18 geothermal power plants in Japan, capable of generating

5,30,000 kilowatts of power.37

38

The GSI has identified 350 geothermal energy locations in India. The most

promising of these is in Puga valley of Ladakh. The estimated potential for

geothermal energy in India is about 10,000 MW.

There are 7 Geothermal Provinces in India : Himalayas, Sohna (Haryana),

Western coast, Cambay, Son-Narmada-Tapti (SONATA), Godavari and Mahanadi.

In Manikaran (in Parvati Valley on river Parvati, Kullu District, Himachal Pradesh),

an experimental geothermal energy plant has been set up.

India’s first Geothermal power plant is being constructed in Tattapani area in

Balrampur distt. (Chhattisgarh) by joint cooperation of NTPC and Chhattisgarh

Renewable Energy Development Agency (CREDA).

Ministry of New and Renewable Energy (MNRE) provides large incentives and

subsidies for Research, Design, Development and Demonstration (RDD&D) for

harnessing geothermal energy in India.

Ministry of renewable energy has planned to generate geothermal energy up to

1000 MW by 2022.

39

40

Lahar

It is a violent type of mudflow or debris flow

composed of a slurry of pyroclastic material, rocky

debris and water. The material flows down from a

volcano, typically along a river valley.

Lahars have the consistency, viscosity and

approximate density of wet concrete: fluid when

moving, solid at rest.

Lahars are extremely destructive: they can flow

tens of metres per second, they have been known

to be up to 140 metres deep, and large flows tend

to destroy any structures in their path.

Notable lahars include those at Mount Pinatubo

and Nevado del Ruiz, the latter of which killed

23,000 people in the town of Armero, Colombia in

1985. The city of Armero was buried under 5

metres of mud and debris.

A lahar travels down a river

valley in Guatemala near the

Santa Maria volcano, 1989

PSEUDO VOLCANIC FEATURES

Those topographic features that resemble the volcanic landforms but are non-

volcanic in origin are known as pseudo volcanic features.

These features include rootless cone, meteorite crater, salt plugs and mud

volcanoes.

Craters

A crater is a depression, usually circular, formed by either the extrusion of

volcanic material or by the impact of any meteorite.

A Rootless Cone is a pseudo-crater which resembles a real volcanic crater, but it

is not of volcanic origin. It does not have an actual volcanic vent from which the

lava has erupted. The rootless cone is characterized by the absence of the magma

conduit which connects the crater to the magma chamber below the Earth's

surface.

Rootless cones are formed by steam explosions as flowing hot lava crosses over a

wet surface, such as a swamp or a lake. The explosive gases break through lava

surface in a manner similar to a phreatic eruption, and tephra builds up crater-like

forms which can appear very similar to real volcanic craters.

A Rootless Cone at Myvatn Lake, Iceland

Meteorite Craters are formed by the impact of falling

meteorites from the space. They resemble like a crater

lake; for example, the Lonar lake (in Buldhan district,

Maharashtra), which has been formed as a result of the

impact of a giant meteorite (during the Pleistocene Epoch

– from about 25,88,000 to 11,700 years ago).

Other examples of meteorite craters include Siberian

crater, Shiva crater (65 m.y.a.) on the Mumbai Offshore

basin, Dhala crater (11 km diametre; largest in India) in

Shivpuri, MP, Ramgarh crater (Rajasthan), etc.

Apart from these, craters developed due to the

anthropogenic activities (resulting from human activities)

are also referred as pseudo-volcanic features (includes

the craters formed by the explosion of bombs, mine

blasts, etc. which resemble the features of a crater).

Fig : Lonar Meteorite Crater

Salt Plugs or Salt Dome

A salt dome is a mound or column of salt that has intruded upwards into

overlying sediments. Salt domes can form in a sedimentary basin where a

thick layer of salt is overlain by younger sediments of significant thickness.

Where conditions allow, salt domes can rise thousands of feet above the

layer of salt from which they began growing.

To develop a salt dome, the pressure on the salt must be high enough to

enable it to intrude the overlying sediments. The pressure must be high

enough to overcome several obstacles. These include the weight of

overlying strata, the strength of overlying strata, frictional forces and the

force of gravity resisting uplift.

Two sources of pressure that have produced salt domes are the downward

pressure of overlying sediment and the lateral pressure of tectonic

movement.

Salt domes are very important to the petroleum industry. As a salt dome

grows, the cap rock above it is arched upwards. This cap rock can serve as

an oil or natural gas reservoir.

As a dome grows, the rocks that it penetrates are arched upwards along

the sides of the dome. This upward arch allows oil and natural gas to

migrate toward the salt dome where it can accumulate in a structural trap.

Under high

pressure, salt

deforms plastically

and behaves like an

intrusive,

deforming and

piercing the

overlying

sediments.

Mud Volcanoes

A mud volcano is a landform formed by the eruption of mud, water, gases, etc.

Mud volcanoes can be formed due to several geological processes.

The mud volcanoes are not true volcanoes as they do not produce Lava and are not

necessarily driven by the activities of magma. Thus, they can be classified under

the pseudo volcanic features.

The Mud volcanoes have usually been found in the subduction zones around the

world. They mostly release methane gas along with smaller quantities of Nitrogen

and carbon dioxide, etc.

The mud produced by mud volcanoes is mostly formed as hot water, which has

been heated deep below the Earth's surface, begins to mix and blend with

subterranean mineral deposits, thus creating the mud slurry exudate.

Ejected materials are most often a slurry of fine solids suspended in water that may

contain a mixture of salts, acids and various hydrocarbons.

A mud volcano may be the result of a piercement structure created by a pressurized

mud diapir that breaches the Earth's surface or ocean bottom.

Mud volcanoes are often associated with petroleum deposits and tectonic

subduction zones and orogenic belts; hydrocarbon gases are often erupted.

Fig : Mud Volcano

49

Please Write Your