excellent subject matter on volcano classification

1. Characteristics of Different Types of Volcanoes and Features
Submitted by :- Manoj Kumar Saini
ID No. :- Ag/Pg/0016/19
Submitted to :- Er. Pawan Kumar
College of Agriculture
Rani Lakshmi Bai Central Agricultural University, NH-75, Near Pahuj Dam,
Gwalior Road, Jhansi (Uttar Pradesh) - 284003

3. A volcano is a landform (usually a mountain)
where molten rock erupts in the Earths crust.
A lot of pressure underground pushes up the
molten rocks.
As pressure in the molten rock (magma) builds
up, it needs to escape somewhere.
This pressure in the molten rock (magma)
comes from the mantle of the Earth and reaches
the crust through cracks.
The molten rock rushes out through a vertical
tunnel called a vent and fills a hollow crater at the
top.
Once the magma erupts through the earths
surface, it is called lava.
As lava cools, it solidifies and forms rocks.

4. Characteristics of volcanoes
A volcano is formed by eruptions of lava and ash.
Volcanoes are usually cone shaped mountains or hills.
When magma reaches the Earths surface it is called lava, when the lava cools, it forms rock.
Volcanic eruptions can happen at destructive and constructive boundaries, but not at conservative boundaries or collision
zone.
Some volcanoes happen underwater, along the seabed or ocean floor.
Common volcanic gases comprise of water vapour, carbon di oxide sulphur di oxide, hydrogen chloride, hydrogen fluoride
and hydrogen sulphide.
Large volcanic eruptions can reflect radiation from the sun and drop average temperatures on earth by around half a
degree.
 Pumice a unique rock (igneous) that can float in water.
It can also used in abrasive and is sometimes used in beauty salons for scrubbing.

6. Based on the
frequency of
eruption
Active
volcanoes
Dormant
volcanoes
Extinct
volcanoes
Based on the
mode of
eruption
Fissure
volcanoes
Shield
volcanoes
Composite
volcanoes
caldera
Cinder cones
volcanoes
Lava domes
volcanoes
Based on the
characteristics of
lava
Volcanoes
with basic
lava
Volcanoes
with acidic
lava

7. Other
type of
volcanoes
Super
volcanoes
Flood
basalt
provinces
Mid ocean
ridge
volcanoes

8. Introduction
Most people have never seen a real volcano
but have learn about them through movies or
books.
So when most people think of a volcano, they
usually conjure up the Hollywood version: a
huge, menacing conical mountain that explodes
and spews out masses of lava which falls on
rampaging dinosaurs, screaming cave people, or
fleeing mobs of betogaed Romans – depending
on their favorite volcano disaster movie.
While those types of volcanoes do indeed exist,
they represent only one species in a veritable zoo
of volcano shape and sizes.

9. Volcanoes type based on frequency eruption
If at the present time it is excepted to erupt or is erupting already.
There are a total of close to 1500 of such volcanoes on the planet. Every year
someone where between 50 and 70 volcanoes will erupt.
Example:- Kilauea which has been erupting since 1983
A dormant volcano is also excepted to have an eruption sometime in the future. Sometimes the difference between a
dormant volcano and active volcano that is preety small. That is because even though a volcano can be dormant for
hundred of years it is steel excepted to have an eruption in the future.629

10. An extinct volcano is a volcano that no one expects will
ever have another eruption. One such volcano is also
located on Hawaii's Big Island and its name is Kohala.
The last time that Kohala erupted was close to 60,000
years ago. As of now scientists do not believe that
volcano will ever be active again.
Example:- Mauna Kea is a volcano which is located on Big island and its last eruption took place 3500-4000 years
ago. However scientists believe that it will erupt again. A dormant volcano could be very dangerous because people
in the surrounding areas are usually not prepared and complacent leaving close to the mountain. Before its eruption
in 1980, Mount St. Helens was dormant

11. Volcano types based on mode of eruption
Fissure volcanoes have no central crater at all.
Instead giant cracks open in the ground and expel
vast quantities of lava.
This lava spreads far and wide to form huge pools
that can cover almost everything around.
When these pools of lava cool and solidify, hat
surface remains mostly flat.
Science the source cracks are usually buried, there
are often nothing “volcano” like to see – only a flat
plain.
Example:-A fissure eruption occurred at the Los Pilas
volcano in Nicaragua in 1952.
1. Fissure volcanoes

12. 2. Shield volcanoes
How to identify:-
 They are not very steep but are far and wider.
 They extend to great height as well as distance.
They are the largest of all volcanoes in the world as the lava flows to a far distance. The Hawaiian volcanoes
are the most famous examples.
Shield volcanoes have low slopes and consist almost entirely of frozen lavas.
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), a type of lava that is very fluid when erupted. For
this reason, these volcanoes are not steep.
They are of low 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 and throws out the cone at the top of the vent and
develops into cinder cone
Example :-
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 the ocean floor and reaching almost 100miles across at its base.
Other famous shield volcanoes include Kilauea, also in Hawaii, and Olympus Mons of Mars.

14. 2.Composite volcanoes
The most majestic of the volcanoes are composite volcanoes.
Shape:- Cone shaped with moderately steep sides and sometimes
have small craters in their summits.
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 a cooler and more
viscous lavas than basalt.
These volcanoes often result in explosive eruptions.
Along with lava, large quantities of pyroclastic materials and
ashes find their way to the ground.
This material accumulates in the vicinity of the vent openings
and leading to the formation of layers, and this makes the mount
appears as composite volcanoes.
Example:-
Famous composite volcanoes include Mount Fuji in Japan,
Mount Shasta and Mount Lassen in California, Mount St. Helens
and Mount Rainier Washington State, Mount Hood in Oregon, and
Mount Etna in Italy.

15. 3.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.
Example:- Yellowstone Caldera, Valles
caldera, Mount Mazama caldera.

16. 4.Cinder cone volcanoes
Cinder cones are simple volcanoes which have a bowl shaped
crater at the summit and steep sides.
 Cinders are extrusive igneous rocks. A more modern name
for cinder is Scoria
 They only grow to about a thousand feet, the size of a hill.
The usually are created of eruptions from a single opening,
unlike a strato-volcano or shield volcano which can erupt from
many different openings.
Cinder cone or scoria cone is a steep conical hill of tephra
(volcanic debris) that accumulates around and downwind from a
volcanic vent.
These volcanoes consist almost entirely of loose, grainy cinders
and almost no lava.
They have very steep sides and usually have a small crater on
top.
Most cinder cones have a bowl-shaped crater at the summit.
Famous cinder cones include Paricutin in Mexico and the one in
the middle of Crater Lake in Oregon.

17. 5.Lava domes volcano
Lava dome volcanoes are formed by
relatively small, bulbous masses of lava too
viscous to flow any great distance;
consequently, on extrusion, the lava piles
over and around its vent.
A domes grows largely by expansion from
within. As it grows its outer surface cools and
hardens, the shatters, spilling loose
fragments down its sides.
Some domes form craggy knobs or spines
over the volcanic vent, whereas others form
short, steep sided lava flows known as “
coulees.”
 volcanic domes commonly occur within
the craters or on the flanks of large
composite volcanoes.

18. 1.Basic lava
Lava will be rich in metallic minerals and has low melting point .
 Hence it has greater fluidity, i.e., less viscosity.
Lava flows far and wide with greater speed.
They forms Shield volcanoes.
2.Acidic lava
Lava rich in in silica and has a relatively high melting point.
They are highly viscous and solidifies quickly.
They forms high volcanic structures with steep slope known as Composite volcanoes
Volcano type based on characteristics of lava

19. Other type of volcanoes
1.Super volcanoes
A super volcano usually has a large caldera and can produce devastation on an enormous,
sometimes continental, scale .
Such volcanoes are able to severely cool global temperatures for many years after the eruption due
to the huge volumes of sulfur and ash released into the atmosphere .
They are the most dangerous type of volcano. Because of the enormous area they may cover, Super
volcanoes are hard to identify centuries after an eruption.
example:-
Yellowstone national caldera in Yellowstone National and Valles caldera in New Mexico ( both
western united states).
Lake Taupo in New Zealand ; Lake Toba in Sumatra, Indonesia; Ngorongoro Crater in Tanzania; and
Krakatoa near Java and Sumatra, Indonesia

21. Submarine volcanoes are common features of the ocean
floor. In shallow water, active volcanoes disclose their
pressure by blasting steam and rocky debris high above the
oceans surface.
In the oceans deep, the tremendous weight of the water
above prevents the explosive release of steam and gases;
however, they can be detected by hydrophones and
discoloration of water because of volcanoes gases .
Pillow lava is a common eruptive product of submarine
volcanoes and is characterized by thick sequence of
discontinuous pillow-shaped masses which form under water.
Even large submarine eruptions may not disturb the ocean
surface due to the rapid cooling effect and increased
buoyancy of water(as compared to air) which often causes
volcanic vents to form steep pillars on the ocean floor
hydrothermal vents are common near these volcanoes, and
some support peculiar ecosystem based on dissolved
minerals.
2.Submarine Volcanoes

22. These volcanoes outpour highly fluid lava that flows for long
distances.
The Deccan Traps from India, presently covering most of the
Maharashtra plateau, are a much larger flood basalt province.
3.Flood Basalt Provinces
Fig. Deccan Traps from India