Volcano Presentation by Yathu - ScienceNavigators.org

8/3/2019 Volcano Presentation by Yathu - ScienceNavigators.org

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What is a Volcano?

A volcano is an opening, or rupture in a planet's

surface or crust, which allows hot magma, volcanic

ash and gases to escape from below the surface.

How are volcanoes formed?

A volcano is formed when plates hit each other.One of the plates goes under the other. This is

where the earth heats and melts the rock into

magma and gases. This can happen as deep

as 100 miles below the earth


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vent

cone

magma chamber

conduit

The volcano includes thesurrounding cone oferupted material.

the vent is the openingfrom which lava flows.Dust, ash, and rockparticles can also bethrown out of the vent!

Parts of the Volcano


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The power of Volcanoes!

Volcanoes can be heard 5000 km away and

can affect people in the range of 50 km.

Volcanoes are powerful enough to destroy an

island and produce 40 m waves when it eruptsand kill 36000 by the wave going 16km in

land.

Many active volcanoes lie under water.

The lava of the volcano can reach 1,250C.


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Volcanoes around the world!

There are more than 1500 potential activevolcanoes around the world.

There are currently no active volcanoes in

Australia but there was one huge eruption 4600

years ago. In South Australia Mt Gambier was the volcano

which erupted 4600 years ago.

Mt St Helens in the USA was dormant for 123

years until it erupted violently in 1980, lowing400 metres off its top and killing 57 people.


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How do volcanoes work?

Pressure from gases in the mantle squeezes the molten rockupwards. The surface of the Earth can swell until it cannot

take any more pressure and then It then explodes with lava.

Hot, molten rock (magma) is buoyant (has a lower

density than the surrounding rocks) and will rise upthrough the crust to erupt on the surface.

When magma reaches the surface it depends on how

easily it flows (viscosity) and the amount of gas

(H2O, CO2, S) it has in it as to how it erupts.Large amounts of gas and a high viscosity (sticky)

magma will form an explosive eruption!

Small amounts of gas and (or) low viscosity (runny)

magma will form an effusive eruption


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Magma is a mixture of molten rockwhich is found under the earth.

What comes out of the volcano when it

erupts is called lava.

Lava is made up of magma and gasessuch as hydrogen sulphide and steam.

Lava flows down the volcano at speeds

of less than 10 km/h and will later cool

to form solid rock.


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Types of Volcanoes!

Explosive Volcanoes Explosive volcanoes are the volcanoes that

when they erupt produce more ash than

lava. When explosive volcanoes erupt they

produce a large area of gas that is

exploded into the atmosphere along with

pieces of extremely hot rocks. The sudden

cooling produces these hot rocks and

shattering of molten rock as it loses its

dissolved gases.


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Explosive Volcanoes Explosive volcanoes have a liquid that lookslike lava, but it is the melted rock of the

volcano.

When an explosive volcano erupts there wont

be any time to evacuate. So volcanologists

constantly watch these volcanoes for signs of

eruption, to have time to evacuate any humanlife from the area.


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Non Explosive volcanoesNon-explosive volcanoes are the volcanoesthat when they erupt lava pours out of the

opening and flows down the mountainside.

When a non-explosive volcano erupts, it

erupts in fountains from the summit or as

curtains of fire from large fissures which split

the volcano's sides.

Non-explosive volcanoes are usually foundclose to oceans or seas, because when a non-

explosive volcano erupts its lava usually flows

into an ocean or the sea.


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Composite volcanoes Composite volcanoes, sometimes known as strato volcanoes,

are steep sided cones formed from layers of ash and lava flows.

Composite volcanoes can rise over 8000 feet.

Examples of composite volcanoes include Mount Fuji (Japan),

Mount St Helens (USA) and Mount Pinatubo (Philippines).

When composite volcanoes erupt they are explosive

Shield volcanoes Shield volcanoes have gently sloping sides and are

formed from layers of lava.

Eruptions are typically non-explosive. Shield volcanoes produce fast flowing fluid [lava]

that can flow for many miles.

Examples of shield volcanoes include the Hawaiian

volcanoes. Although these eruptions destroy

property, death or injury to humans rarely occurs.


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Dome

Dome volcanoes have much steeper sides than shield volcanoes.

This is because the lava is thick and sticky. It cannot flow very far before it cools and hardens. An example is

Puy de Dome in the Auvergne region of France which last

erupted over 1 million years ago.


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Such as:

The Earths moon

Mercury Venus

Mars

Io (A moon of Jupiter).


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