SCIENCESubmitted by Tan Zi Jie

(30)1P1

Video

Here is a live video of the Eyjafjallajokull volcano eruption.

http://www.youtube.com/watch?v=f1ztg0wUqKY

http://www.youtube.com/watch?v=NWB0TrrjtAU&feature=related

Objectives

My PowerPoint presentation is about the science of volcano activity using the recent eruption in Iceland as an illustration.

The volcanic smoke and ash from the volcano in Eyjafjallajokull, Iceland, has disrupted many flights from, to and within Europe, leaving many people stranded in airports all over the world.

Here is a picture to show how bad the conditions are in Iceland. Visibility has dropped almost to zero.

This picture shows the volcano spewing smoke on an earlier date.

The Mechanics of an Eruption

Eruptions begin with a build up of pressure in the magma chamber beneath the volcano.

As the steam and gas jets out , they carry with them clouds of ash and larger fragments of the broken plug of magma called volcanic bombs or tephra.

Bubbles of steam and gas form and swell rapidly inside the magma, and burst out like the froth from a violently shaken bottle of fizz.

With the volcanic plug out of the way, magma surges up and out of the volcano and flows down as larva.

The Anatomy of a Volcanic Eruption

Main Vent

Cone of ash, rock and lava.

dyke

Cloud of ash and steam

Volcanic bomb

Side vent

Larva flow

The way volcanoes erupt usually takes a long time and this is how volcanoes erupt. 

First a volcano makes something called magma from melted rock.  The magma goes through a circulation.  It has to form at the bottom of the volcano and then start its way up the main vent.

The main vent is a hole that is in the volcano and when the volcano is ready to erupt the lava is at the top of the main vent.  The magma goes up the main vent slowly while it is still getting hotter.  When the magma is about half way up the main vent it turns into lava. 

Lava is a very hot liquid which burns the remaining rocks from the magma.  The lava slowly continues up the main vent.  While going up the lava continues to get hotter and hotter.

Ash and rocks are collected and the lava is getting hotter and hotter while the lava is continuing its way up the main vent.  When the lava is at the top of the main vent the volcano erupts. 

The lava blasts out of the volcano along with ash, rocks, and a cloud of dust that is very thick. . 

The ash and rock crumble to the ground, but the lava is either moving down the volcano side very slowly or at a high speed.  The lava burns down almost everything in its way, and it sometimes leaves bits of things burning. 

The lava from the volcano can cool fast, or sometimes  the lava will slowly cool down from its intense heat.  Lava that cools slowly forms igneous rocks.  There are many types of igneous rocks. 

Volcanoes can damage themselves in the explosion.  A volcano literally blows its top off.   One of the volcanoes that has blown its top from an explosion is Mt. St. Helens. 

Volcanoes can be under water or on land.  Volcanoes that are under water take a longer time than if they are on land because they are under water the water slows down the magma and lava but if the volcano is on land the lava and magma can move quicker up the main vent. 

It just depends on the environment how fast the volcano can make the magma and the lava move up the main vent and this will thus determine how long it takes for the volcano to erupt. 

If the volcano is under water the cooled lava will probably make an island.  The Hawaiian Islands is an example of island made by a chain of volcanoes.

Types of Volcano

Volcanoes come in different shapes and sizes

Cone volcano – develop where the plates are pushing

together - magna is trapped below the ground,

making it so acidic and so thick and sticky that it clogs up the volcano and then erupts sporadically and dramatically

Shield volcano- is formed where plates are pulling apart- the magna is less acid and runnier; it

reaches the surface easily and floods out steadily as lava to form a gentle slope that looks like an upturned shield

Earthquakes and Volcanoes occur in the regions where the tectonic plates meet

History of the Eyjafjallajokull Volcano

Is one of the smaller glaciers of Iceland, situated to the north of Skógar and to the west of Mýrdalsjökull. The icecap of the glacier covers a volcano with a summit elevation of 1,666 metres (5,466 ft). The volcano has erupted relatively frequently since the Ice Age.

Now, you may wonder, since there is only smoke coming from the volcano, then why can’t the plane just fly through?

Well, the next few slides will explain the reason.

What is volcanic ash?

First, we have to know what is volcano ash.

Well, it is plumes of dust spewed out by volcanoes which usually contain tiny particles of glass, pulverised rock and silicates.

The result is a cloud of potentially deadly material resembling sandpaper.

The Jet Engine• In a basic jet engine,

air is sucked in at the front, then compressed and forced into a combustion chamber.

• Fuel is added and burnt in the chamber.

• This produces very hot gases, which shoot out of the back of the engine.

• As the gases escape, they drive the aircraft forward. They also push round a turbine, which turns the compressor that draws in air at the front of the engine.

Why is it a hazard to aviation?

The abrasive effect of the ash can strip off vital aerodynamic surfaces and paralyse an aircraft engine. Aircraft avionics and electronics can also be damaged.

Piton tubes, or speed sensors - whose sensitivity to ice or foreign objects was highlighted during an investigation into the loss of an Air France jet last year - can get bunged up and fail. The cockpit windshield can turn opaque, scoured by ash. Ash can bring clouds of sulphuric and hydrochloric acid.

What happens inside the jet engine?

The high speeds and temperatures inside a modern jet engine are its own downfall when invaded by laval dust.

Volcanic ash fragments are just a few millimetres wide, very hard and very sharp. They can get inside the engine and other parts of the plane and wear away everything they come into contact with.

First, abrasive ash can damage compressors which squeeze air ready for combustion, making them less aerodynamically stable.

From there, pressurised air is forced into the combustion chamber which is so hot :- 1,200-2,400 degrees Celsius at cruise altitude - that the fragments melt, then meld. Then this liquid rock smashes into colder parts and solidifies like cooled glass.

Nozzles designed to shoot air towards the engine's turbines, which turn the engine's moving parts, start to thicken with lava. As a result ventilation is blocked and the nozzles burn too hot.

Finally clumps of lava cut the space for air to escape and can provoke an engine stall, shooting flames from the back.

Why can't aircraft simply avoid the dust clouds?

Volcanic ash is invisible to aircraft weather radar and is often not immediately noticed by pilots.

The first warning you get is a sulphurous smell and perhaps some “St Elmos fire" (a glow caused by a type of electrical discharge).

Have there been any accidents due to volcanic ash?

Dozens of minor cases have been reported but no crash has been blamed on ash. Yet there have been two escapes.

On June 24th, 1982, the captain of a British Airways jumbo jet en route from Kuala Lumpur to Perth, Australia, came on the speaker system at around 37,000 feet and calmly told the 247 passengers on board that all four of its engines had failed.

In an incident that went down in aviation history, Captain Eric Moody glided the jet down more than 20,000 feet and managed to restart one engine at 13,000 feet followed by others, according to the Flight Safety Foundation.

It was only later that investigators found the combination of engine failure, an eerie luminous glow around the plane and acrid smoke inside the cabin had been caused by flying into a cloud of volcanic ash from the eruption of Mount Galunggung.

The aircraft landed safely on three engines but the incident prompted new flight procedures and international exercises.

On December 15th, 1989, all four engines failed when a KLM jumbo jet from Amsterdam flew into a cloud that turned out to be volcanic ash while descending to Anchorage, Alaska.

The engines resumed working and the plane landed safely but badly damaged.

That incident was blamed on lack of sufficient information provided to the crew, the Flight Safety Foundation says.

Credits

Science Encyclopedia , Bardfield Press The Oxford Children’s Encyclopedia of Sci

ence & Technology, Oxford University Press

http://www.irishtimes.com www.google.com http://library.thinkquest.org www.youtube.com