Volcanoes form when magma rises up from below the Earth's crust and erupts. There are three main types of volcanic eruptions that differ based on the speed and viscosity of the magma: magmatic, phreatomagmatic, and phreatic. Monitoring volcanoes for changes in shape, temperature, and seismic activity can help predict eruptions and allow for evacuation planning to reduce risk to humans. The largest volcanic eruption in history was the Lake Toba eruption in Indonesia around 75,000 years ago.

1. BY : SAKSHI .R. HANDORE

2. INDEX
1. What is volcano?
2. Types of volcanoes
3. Magmatic eruptions
4. Phreatomagmatic eruptions
5. Phreatic eruptions
6. Volcanic Explosivity Index (VEI)
7. Formation of volcano
8. Effects of volcano
9. Risk reduction of volcanic eruption
10. Example of volcanic eruption
11. Facts about volcano

3. WHAT IS VOLCANO?
A volcano is a rupture in the crust of a planetary-mass
object, such as Earth, that allows hot lava, volcanic ash,
and gases to escape from a magma chamber below the
surface.
The word volcano is derived from the name of Vulcano, a
volcanic island in the Aeolian Islands of Italy.
The study of volcanoes is called volcanology.

4. TYPES OF VOLCANO
There are three different types of volcanic eruptions :
Magmatic eruptions Phreatomagmatic eruptions Phreatic eruption
a. Hawaiian d. Peléan
b. Vulcanian e. Plinian
c. Strombolian
a. Surtseyan
b. Submarine
c. Subglacial

5. MAGMATIC ERUPTIONS
Magmatic eruptions
produce juvenile clasts during explosive decompression from gas
release.
Hawaiian : Hawaiian eruptions are the calmest types of volcanic events,
characterized by the effusive eruption of very fluid basalt-
type lavas with low gaseous content.
Strombolian : Strombolian eruptions are driven by the bursting of gas
bubbles within the magma. Strombolian eruptions eject volcanic
bombs and lapilli fragments that travel in parabolic paths before
landing around their source vent.
Vulcanian : In Vulcanian eruptions, intermediate viscous magma within
the volcano make it difficult for vesiculate gases to escape.
Peléan : In Peléan eruptions, a large amount of gas, dust, ash, and lava
fragments are blown out the volcano's central crater.
Plinian : In plinian eruptions he narrow confines of the conduit force the
gases and associated magma up, forming an eruptive column.

6. PHREATOMAGMATIC ERUPTIONS
Phreatomagmatic eruptions are eruptions that arise
from interactions between water and magma. They
are driven from thermal contraction of magma
when it comes in contact with water.
Surtseyan : A Surtseyan eruption (or hydro volcanic)
is a type of volcanic eruption caused by shallow-
water interactions between water and lava.
Submarine : Submarine eruptions are a type of
volcanic eruption that occurs underwater.
Subglacial : Subglacial eruptions are a type of
volcanic eruption characterized by interactions
between lava and ice, often under a glacier.

7. PHREATIC ERUPTIONS
Phreatic eruptions (or steam-blast eruptions)
are a type of eruption driven by the expansion
of steam. When cold ground or surface water
come into contact with hot rock or magma
it superheats. and explodes.
When cold ground or surface water come into
contact with hot rock or magma
it superheats and explodes, fracturing the
surrounding rock and thrusting out a mixture
of water, ash, volcanic bombs, and volcanic
blocks.

8. Volcanic Explosivity Index (VEI)
The Volcanic Explosivity
Index (commonly shortened to VEI) is
a scale, from 0 to 8, for measuring
the strength of eruptions.
The vast majority of volcanic eruptions
are of VEIs between 0 and 2.

9. FORMATION OF VOLCANO
Volcano eruptions happen when magma erupts from beneath the
Earth's crust. When a volcano erupts, the magma becomes lava and
shoots into the air, eventually running down the side of the
volcano.
• Subduction Zones : Volcanoes emerge in subduction zones,
where two tectonic plates collide.
One tectonic plate moves under the another plate, pushing it down
into the upper mantle. This causes a change in the temperature
and pressure above the submerged plate. Magma then forms as a
result of lower pressure and increased temperature.

10. Formation of Magma : Lower pressure above the submerged plate and
below the top plate causes the rocks in the mantle to begin melting. Magma is
less dense than rocks, which means that it is also lighter.
Because magma is hot, it rises through the Earth's crust, and because rocks are
cold and dense, they fall through the Earth's crust.
Before volcanoes erupt, the magma sloshes around in the upper mantle. Magma
may cool and form igneous rocks and crystals below the surface, but it may
also move into magma chambers,

11. EFFECTS OF VOLCANO
On environment : The hazards closer to the volcano include, flows
of mud, gases and steam, earthquakes, blasts of air, and tsunamis.
Carbon dioxide emitted from volcanoes adds to the
natural greenhouse effect. Along with magma and steam (H2O),
carbon dioxide and sulphur dioxide, carbon monoxide, and various
organic compounds, as well as heavy metals (mercury, lead, gold)
are emitted out.
On humans : Among the hazards in distant areas are the effects of
toxic volcanic ashes and problems of the respiratory system, eyes
and skin, as well as psychological effects, injuries, transport and
communication problems, waste disposal and water supplies issues,
collapse of buildings and power outage.
On aircrafts : The ash particles melts by the high operating
temperature of aircrafts . The melted particles then adhere to the
turbine blades and alter their shape , disrupting the operation of
turbine.

12. RISK REDUCTION OF VOLCANIC ERUPTION
Volcanoes are natural hazards that can be unpredictable, there are a number of
strategies that are used to reduce the risk
.
MONITORING : Prior to volcanic eruptions
volcanoes tend to change shape as magma rises
through them. Tiltmeters and satellites (through
GPS) are used to detect changes in the surface
shape of a volcano.
Thermal heat sensors can be utilized to detect
changes in the surface temperature of the
volcano. As magma rises this causes an increase
in surface temperature of the volcano. As magma
rises this can cause small earthquakes.
Seismometers and lasers are used to monitor the
earth movements that can often occur prior to a
volcanic eruption.
Tiltmeter

13. • PREDICTION : By monitoring the movement of tectonic plates and changes in the
surface of the volcano scientists can predict the likelihood of a volcanic eruption
and forecast which areas should be prepared for one. Predicting when a volcano is
at risk of eruption allows time for evacuation plans to be initiated.
• PROTECTION : Lava flows, lahars and ash fallout cannot be protected against. As
the result of this evacuation is the only real way of reducing the risks associated
with volcanic eruptions. Lava from the volcano Eldfell on the island of Haimey
threatened the harbour and town. For over 4 months the lava was blasted with sea
water. The lava flow was re-directed and the harbour was saved, though 1/5th of
the town was lost.
• PLANNING : One of the most effective ways of reducing the risk of a volcanic
eruption is having an evacuation plan. This involves ensuring evacuation strategies
are in place along with emergency shelter and food supplies being planned for.
Local people can also be educated about actions they can take to reduce the risk of loss
of life or injury.

14. EXAMPLES OF VOLCANO ERUPTION
1. KRAKATOA
The August, 1883 Krakatoa explosion altered sunsets
around the world, completely demolishing the
Indonesian island. The eruption released nine
cubic kilometers of magma.
2. LAKE TOBA
The largest volcanic lake in the world, Lake Toba was
created by an explosion
3. LAKE TAUPO
That eruption released enough lava to coat all of
Europe in a two-inch thick layer of magma. The
blast was so large, it took 17,000 years for the
climate to return to pre-eruption conditions.

15. FACTS ABOUT VOLCANO
• The world’s largest active volcano is Mauna Loa in Hawaii standing at
4,169m!
• The “Ring of Fire”, a 40,000 km Horseshoe shaped area of the Pacific
Ocean, is home to 90% of all volcanoes on the Earth.
• The soil near volcanoes is said to be rich and fertile which is why some
people actually set up home on the slopes!
• Geologists estimate that around 1,300 volcanoes on land erupted in the
last 10,000 years and in the underwater volcanoes 6,000 erupting in the
last 10,000 years.