volcanoes devastating disaster

1. VOLCANOES🌋
The Most Devastating Disaster

2. What are volcanoes?🤔
■ A volcano is a rupture(hole or crater) 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.
■ Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic
plates that float on a hotter, softer layer in its mantle.[1] Therefore, on Earth,
volcanoes are generally found where tectonic plates
are diverging or converging, and most are found underwater. For example,
a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by
divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused
by convergent tectonic plates. Volcanoes can also form where there is stretching
and thinning of the crust's plates, e.g., in the East African Rift and the Wells
Gray-Clearwater volcanic field and Rio Grande Rift in North America.

3. Types of volcanoes🌋🗻
■ An active volcano is a volcano that has had at least one eruption
during the past 10,000 years. An active volcano might be erupting or
dormant.
■ An erupting volcano is an active volcano that is having an eruption at
least once in 10000 years.
■ A dormant volcano is an active volcano that is not erupting, but
supposed to erupt again.
■ An extinct volcano has not had an eruption for at least 10,000 years
and is not expected to erupt again in a comparable time scale of the
future.

4. 1.Active volcano🌋
■ There is no consensus among volcanologists on how to define
an "active" volcano.The lifespan of a volcano can vary from
months to several million years, making such a distinction
sometimes meaningless when compared to the lifespans of
humans or even civilizations. For example, many of Earth's
volcanoes have erupted dozens of times in the past few thousand
years but are not currently showing signs of eruption. Given the
long lifespan of such volcanoes, they are very active. By human
lifespans, however, they are not.
■ Scientists usually consider a volcano to be erupting or likely to
erupt if it is currently erupting, or showing signs of unrest such as
unusual earthquake activity or significant new gas emissions. Most
scientists consider a volcano active if it has erupted in the last
10,000 years (Holocene times)—the Smithsonian Global Volcanism
Program uses this definition of active. Most volcanoes are situated
on the Pacific Ring of Fire. An estimated 500 million people live
near active volcanoes.
■ Examples of active volcanoes are: Kilauea in Hawaii, Mount Etna in
Italy and Mount Stromboli also in Italy which has been erupting
almost constantly for the last 2000 years.

5. 2.Dormant volcano🗻
■ It is difficult to distinguish an extinct volcano from a
dormant (inactive) one. Dormant volcanoes are those
that have not erupted for thousands of years, but are
likely to erupt again in the future.[17][18] Volcanoes are
often considered to be extinct if there are no written
records of its activity. Nevertheless, volcanoes may
remain dormant for a long period of time. For
example,Yellowstone has a repose/recharge period of
around 700,000 years, andToba of around 380,000
years.[19] Vesuvius was described by Roman writers as
having been covered with gardens and vineyards before
its eruption of 79 CE, which destroyed the towns of
Herculaneum and Pompeii. Before its catastrophic
eruption of 1991, Pinatubo was an inconspicuous
volcano, unknown to most people in the surrounding
areas.Two other examples are the long-
dormant Soufrière Hills volcano on the island
of Montserrat, thought to be extinct before activity
resumed in 1995, and Fourpeaked Mountain in Alaska,
which, before its September 2006 eruption, had not
erupted since before 8000 BCE and had long been
thought to be extinct.

6. 3. Extinct volcano
■ The extinct volcano no longer has a lava supply. An extinct volcano is
no longer near an active geologic hot spot, if it ever was.
■ Volcanologists sometimes can't tell whether a volcano is extinct
or dormant. A caldera that has not produced an eruption in tens of
thousands of years is likely to be considered inactive. Dormant
volcanos may still erupt, whereas extinct ones cannot.
■ There are many examples of extinct volcanoes.
■ Ben Nevis, the tallest mountain in the United Kingdom.
■ Hawaiian–Emperor seamount chain in the northern Pacific Ocean
■ Huascarán in Peru
■ Kyushu-Palau Ridge in the Philippine Sea
■ Mount Buninyong in Victoria Australia[8]
■ The Nut in Tasmania Australia
■ Tamu Massif in the Northwest Pacific Ocean
■ Waw an-Namus in Lybia
■ Edinburgh Castle in Scotland is located on a dolerite plug, the remnant
of a volcano that went extinct many millions of years ago.

7. Advantages and Disadvantages of
volcanoes🌋
■ Advantages
■ 1. Atmospheric cooling
■ One of the shorter-term benefits could be observed with recent large eruptions including 1991’s Pinatubo eruption in the Philippines
and 1982’s El Chichón eruption in Mexico, which both exploded ash and sulfur gas into the stratosphere, according to Gregg.
■ 2. Land forming
■ A long-term benefit of volcanic activity is seen in the Hawaiian Islands’ very existence.
■ “We’re seeing this right now on the Big Island of Hawaii with Kilauea’s current eruption, as lava is pouring into the ocean and creating
new land,” Gregg said. “All of the land in the Hawaiian Islands was created this way.” This land formation can take thousands of years,
she added.
■ Disadvantages
■ 1) It performs a lot of destruction.
■ 2) The volcanic eruptions also produce harmful gases.
■ 3) The lava heat act as a booster for the global warming.
■ 4) The lava flow often cause many deaths.
■ 5) The lava flow often cause wild fire in the nearby forestlands.

8. The most
devastating
Volcanic Eruption
■ Mount Tambora experienced several centuries
of dormancy before 1815, caused by the
gradual cooling of hydrous magma in its closed
magma chamber.Inside the chamber at depths
between 1.5 and 4.5 kilometres (0.93 and
2.80 mi), the exsolution of a high-pressure fluid
magma formed during cooling
and crystallisation of the magma. An over-
pressurization of the chamber of about 4,000–
5,000 bar (400–500 MPa; 58,000–73,000 psi)
was generated, with the temperature ranging
from 700–850 °C (1,292–1,562 °F). In 1812,
the volcano began to rumble and generated a
dark cloud.
■ On 5 April 1815, a very large eruption occurred,
followed by thunderous detonation sounds
heard in Makassar on Sulawesi 380 kilometres
(240 mi) away, Batavia (now Jakarta)
on Java 1,260 kilometres (780 mi) away,
and Ternate on the Molucca Islands 1,400
kilometres (870 mi) away. On the morning of 6
April, volcanic ash began to fall in East
Java with faint detonation sounds lasting until
10 April. What was first thought to be the
sound of firing guns was heard on 10 April
on Sumatra, more than 2,600 kilometres
(1,600 mi) away.

9. • At about 7 pm on 10 April, the eruptions
intensified.Three plumes rose up and merged.The
whole mountain was turned into a flowing mass of
"liquid fire“. Pumice stones of up to 20 centimetres
(7.9 in) in diameter started to rain down around
8pm, followed by ash at around 9–10pm.
• Pyroclastic flows cascaded down the mountain to
the sea on all sides of the peninsula, wiping out the
village ofTambora. Loud explosions were heard until
the next evening, 11 April.The ash veil spread as far
as West Java and South Sulawesi.A nitrous odour
was noticeable in Batavia, and heavy tephra-tinged
rain fell, finally receding between 11 and 17 April.

10. A PRESENTATION BY SAUMYA PATEL.
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