Volcanoes

If you were standing on the shore a Tsunami would look like rapidly advancing tide. It may also look like a wall of water. While earthquakes cannot be predicted accurately Tsunami’s can once the earthquake or volcanic eruption has been observed. Once a Tsunami alert has been triggered people living on the coasts simply abandon everything and make for higher ground as quickly as possible. Have a look at the link below to see some footage of the devastating Tsunami which hit Japan in 2011.

Most Unbelievable footage of Japanese Tsunami I have seen so far (taken from helicopter)

<a href="https://www.youtube.com/watch?v=3xKMFzKOIfQ">Japanese Tsunami Footage</a>

On May 18th, 1980 a volcano in Washington state in the USA, Mount St. Helens erupted. A giant column of ash rose from the eruption bringing darkness to much of the state and also spreading across much of the US and Canada. Mount St. Helens is one of the chain of volcanoes that make up the Pacific Ring of Fire.

On August 27th 1883 the Volcano on the island of Krakatoa erupted producing the deadliest volcanic eruption in history. Two thirds of the island collapsed during the eruption with the death toll estimated to be between 37,000-120,000 people. The island was actually made up of three volcanoes. The first to erupt was Perboewatan in the North of the island. It started to erupt on May 20th. On August 11th it was reported that a second volcano Danan, in the centre of the island had started to erupt. Between Perboewatan and Danan numerous other vents began to open up.

Shield Volcanoes are flat. They are caused when the lava can escape without causing an explosion. The lava just flows gently down the side of the mountain. They are usually flat or mountains with shallow slopes. Examples include the Volcanoes in Hawaii or Mount Etna. 

Interesting and Amazing Facts about Volcanoes

About 1,900 volcanoes on Earth are considered active and are likely to explode again. In 1883 Krakatau in Southeast Asia erupted, releasing 200 megatrons of energy. This is the same as 15,000 nuclear bombs. It is reported that this caused the loudest sound in history. Some people actually live on the slopes of volcanoes as the soil there is rich and fertile and great for growing some crops. Maleo birds use the heat from volcanoes to help hatch their eggs. They bury their eggs in the soil or sand near to volcanoes. When the chicks hatch they claw their way up to the surface.

The word volcano comes from the name of the Roman god of fire, Vulcan. Volcanoes are usually located where tectonic plates meet. Over 75% of the volcanoes on Earth are found in the Pacific Ring of Fire. Hot liquid rock under the Earth’s surface is known as Magma. It is only called Lava when it reaches the surface of the Earth. The largest volcano in our Solar System is actually on Mars and is called Olympus Mons. It is 600km wide and 21km (that’s over twice the height of Mt Everest). Volcanoes are also found on the ocean floor and even under icecaps. Common volcanic gases include water vapor, carbon dioxide, sulfur dioxide, hydrogen chloride, hydrogen fluoride and hydrogen sulfide.

As the pressure builds the crust comes under huge pressure. when the pressure becomes too much the magma pushes through in an eruption. It is not just lava that erupts. Gas, rocks and dust are also thrown out in the explosion. So now you know how a volcano erupts lets have a look at some other interesting things about volcanoes.

On the second day the eruption continued with pyroclastic flows traveling down the sides of the mountain at hurricane speeds. The hot gases, pumice and other debris in the flows killed all the people who remained in Pompeii and Herculaneum many where they stood.

These Pyroclastic Flows can reach speeds in excess of 200km per hour and devastate everything in their path. Temperatures inside these giant clouds can reach 800C. These flows can also sometimes travel across water. Check out the links to the videos of the devastation caused by Pyroclastic Flows on the next page.

During the eruption of Krakatoa in 1883 it is estimated that at least 10% of the deaths were due to ash flows. In fact  such was the force of the Pyroclastic Flow that it travelled as much as 40km across the sea to the island of Sumatra in Indonesia.

By August 25th a black cloud of ash blew almost 27km into the sky. By now a large number of ships had begun to come closer to the island to watch. Explosions happened every 10 minutes and pumice up to 10cm in diameter began to fall on the decks. On August 27th 4 massive eruptions ripped the island apart. The eruptions triggered large pyroclastic flows, tsunamis and a large landslide.

The seven major plates include the African, Antarctic, North American, South American, Eurasian, India-Australian, and the Pacific plates. There are also some monitors plates such as the Arabian, Caribbean and Nazca plates. 

These plates sometimes pass under or over each other which cause mountains to rise. The Himalayan Mountains, including Mount Everest, were formed by the Indian Plate and the Eurasian Plate pushing together and forcing the land up.

Tsunami (soo-NAH-mee) is a Japanese word meaning harbour wave. Volcanic eruptions can also cause Tsunami’s. A tsunami is a large ocean wave cause by either a volcanic explosion or an earthquake underwater. Tsunamis are not tidal waves. as these are caused by the forces of the moon, sun, and planets upon the tides. On average, two tsunamis occur per year throughout the world.

The eruption of Vesuvius in 79 AD is one of the most famous. Clouds of hot ash and gas rose up to almost 30km in the sky.

Wealthy Romans lived and had vacation towns near the volcano. A famous Roman writer, Pliny the younger was in the area and wrote about what he saw. It is the first documented account of a volcanic eruption.

<a href="bookcreator://page/Uy39-7AqTs6u1nDV0uSyzQ">Glossary</a>

<a href="bookcreator://page/R8JGhR8DSIeKmHNnh5H1WQ">Effects of a Volcano</a>

<a href="bookcreator://page/Wl4B3u_4RByUQJ0_sTkgSg">What is a Volcano?</a>

<a href="bookcreator://page/4LpefYMLQpmkzObLqUMlyg">Famous Volcanic Eruptions</a>

<a href="bookcreator://page/cyAu-UPMSnSL-dvG-2ptag">Different Types of Volcanoes</a>

<a href="bookcreator://page/8K1ImcjQQnKB1EUOfBAgmg">Interesting Facts</a>

<a href="bookcreator://page/TvxgKUAvR6CG3icDe2Mx2w">Plate Tectonics</a>

Clicking on the image below on any page will bring you back to this page. 

All images and videos created or sourced through Creative Commons Licence.

The deadly Pyroclastic flows destroyed the towns of Pompeii and Herculaneum. The towns were completely buried. The eruption lasted two days and began with a column of black ash rising high above Vesuvius. Pliny write that on the first day ash and pumice blew out of the volcano for up to 20 hours covering Pompeii with layers of pumice nine feet deep. While pumice is light and can actually float in water this amount of it completely buried the town.

When Magma reaches the surface it is called Lava. This lava cools in the air on the surface and returns to a solid form becoming a rock again. Over time this creates a mountain known as a volcano. As more and more eruptions occur the mountain grows larger.

When a volcano erupts the magma in the magma chamber pushes towards the surface. Remember the magma that has already reached the surface has cooled so it has formed a crust. If you have ever watched a pot boiling with the lid on you will have an idea of what happens. As the heat and pressure builds under the lid the lid starts to move. It is the same with a volcano.

As if a Volcano exploding wasn&apos;t enough to be worrying about eruptions can also trigger other events that are just as deadly.

You would think that lava coming towards you would be the biggest thing to worry about but you would be wrong. Sometimes volcanoes trigger Pyroclastic Flows. 

During an eruption large amounts of dust, ash and rocks are hurtled into the air. But sometimes the side of the volcano will collapse causing this to travel down the mountainside.

Although you might not notice it the land under our feet is constantly moving. Of course it is moving so slowly that we don&apos;t notice it.

If you look at the image on this page you will see the different layers of the Earth. The part that is moving is called the lithosphere. It is made up of the Earth&apos;s crust and a part of the upper mantle. The lithosphere is constantly moving. But it does not all move together. The Earth is made up of plates which move around sometimes in different directions.

These is a short slideshow of some photographs of the eruption of Mount St Helens,

Large volcanic eruptions cause clouds of dust and ash to rise into the sky and can reflect radiation from the Sun. this can lead to a drop in temperatures on Earth by around half a degree. There have been several examples of this over the last century. Pumice is a unique volcanic rock that can float in water (it is also sometimes used in beauty salons for removing dry skin) 1 in 20 people in the world live within the “danger range” of an active volcano. Lava temperatures can reach 1,250°C. If you tried to measure the temperature using a glass thermometer the glass would melt. The world&apos;s largest active volcano is Mauna Loa in Hawaii standing at 4,169m. In A.D. 79, Mount Vesuvius erupted, destroying the Italian town of Pompeii. The ash deposits preserved the town and the remains of the people within it (it might sound a little gruesome but you can visit and still see them today).

These are some definitions of words you will come across in this book.

MAGMA - Magma is the liquid rock inside a volcano. LAVA - Lava is the liquid rock (magma) that flows out of a volcano. ACTIVE VOLCANO - An active volcano is one that erupts regularly. DORMANT VOLCANO - A dormant volcano is one that has not erupted for many years, although there is still some activity deep inside. EXTINCT VOLCANO - An extinct volcano is a volcano that is no longer active.

We often think of a Volcano as having a Cone shape but this is not always the case. Volcanoes come in many shapes including;

A Resource for the Primary School Classroom Cormac Cahill

Deep within the Earth we find something called Magma. Magma is hot liquefied Rock. Imagine a temperature so hot that it turns rocks into liquid and you will have an idea of how hot we are talking about. Sometimes this magma builds up in an area in something we call a Magma chamber. With all of this heat and magma pressure sometimes builds. The Magma finds a weak spot and will start rising quickly to the surface. This is called an eruption. Gases and rock shoot up through the opening created by the pressure.

This short video will explain to you how a Volcano erupts.

An extinct volcano is one which has erupted in the distant past and it will never erupt again.

Examples of Extinct Volcanoes include; Aconcagua in Argentina Mount Kenya in Kenya Mount Ashitaka in Japan Mount Buninyong in Australia

On May 18th, a large magnitude 5.1 earthquake shook the area and caused the north side of the mountain to collapse and a giant landslide to form. It was the largest landslide in recorded history. The landslide travelled at over 150km per hour down the mountain wiping out everything in its path. 

A few seconds later the north side of the mountain exploded sending a hot cloud of gas and debris out destroying everything in its path. Entire forests were destroyed.

A dormant volcano is one which has not erupted in a long time. But there is always a chance it will in the future.

Examples of Dormant Volcanoes include; Mauna Kea in Hawaii Sete Cidades in Portugal Mount Teide in Spain Mount Arafat in Turkey Mount Kilimanjaro in Tanzania

Terrifying Pyroclastic Flows Sinabung Volcano Eruption in 4K Ultra HD

<a href="https://www.youtube.com/watch?v=-iSFM-T-F_0">Sinabung Volcano Pyroclastic Flow</a>

Dome collapse and pyroclastic flow at Unzen Volcano

<a href="https://www.youtube.com/watch?v=Cvjwt9nnwXY">Dome Collapse and Pyroclastic Flow at Unzen Volcano</a>

•	The first eruption began at 5:30 a.m. The explosive eruption on Perboewatan volcano cause a large pyroclastic flow to descend the mountain in turn causing a massive tsunami. 	•	At 6:44 a.m. the Danan volcano exploded again forming a pyroclastic flow that caused further tsunamis to head eastward and westward away from the island. 	•	The 10:02 a.m. volcanic explosion was so loud that it was heard over 3,000km away in Perth, Australia. This explosion was so large that it created a tsunami 30 meters high.

	•	A landslide at 10:41 a.m. tore off half of the third volcano on the island, Rakata. By now the island had almost disappeared.

Ninety percent of the people were killed by tsunamis. Ten percent were killed by the pyroclastic flows that flowed across the ocean to nearby Java and Sumatra and which were still hot enough to burn people to death. In 1927 a new island began to form and was named Anak Krakatoa (Child of Krakatoa). It has been erupting off and on since 1927 and is constantly monitored by geologists.

This is what remains of the island now. You can see the new island in the centre.

The speed a Tsunami travels at depends on the depth of the water. The deeper the water the fast it moves. They can reach speeds in excess of 700km per hour. Tsunamis range in size from just a few centimetres to over 30metres in height.

Lava Domes are formed when the erupting lava is too thick to flow. It creates a steep sided Volcano as the lava piles up near the vent. 

The town of Pompeii with Vesuvius in the background.

The buried cities were forgotten for almost 1700 years when Pompeii was accidentally discovered preserved under the layers of pumice.

Today more than three million people still live around the base of Vesuvius. It is still considered one of the most dangerous volcanoes in the world.

Sometimes the plates even hit each other or rub off each other causing earthquakes. In some places the plates are actually pulling away from each other. These are called Divergent Boundaries. This causes Magma to pour through and is generally where Volcanoes form.

Luckily most people had been evacuated before the eruption but 57 people were killed and the damage caused by the eruption cost over $1 billion of damage. Roads, bridges, and railways were washed away in the landslide as well as over 200 houses. In 2004, Mount St. Helens became active again. It was quiet until 2008 when further small eruptions occurred. Geologists continue to keep a close eye on Mount St Helens.

These images show what Mount St helens looked like before and after the eruption.

Composite Volcanoes occur when the lava is thick and sticky. Composite Volcanoes usually have steep sides and are made up of lots of different types of rocks. They are also known as Strata Volcanoes. 

An Active Volcano is one which has recently erupted and there is a good chance it will erupt again soon. 

Examples of Active Volcanoes include; Eyjafjallajökull in Iceland Mount Vesuvius in Italy Sakurajima in Japan Mount Merapi in Indonesia Mauna Loa in Hawaii

Geologists had been watching the volcano as they believed it could erupt but they could not say when. All through March and April the volcano had become more active sometimes sending large clouds of steam into the air. In April they noticed a large bulge appear on the north side of the volcano. They knew that this bulge was a result of the pressure building inside the volcano.

You can see the bulge on the mountain here.

ASH - Ash are very small fragments of lava or rock blasted into the air by volcanic explosions. PUMICE - It is a light-coloured volcanic rock containing lots of bubbles from trapped gases.

Lassen Volcanic National Park California, USA

Cinder Cone Volcanoes have circular or oval shaped cones. As the lava erupts it breaks into small pieces that fall back to the ground as cinders around the vent. 

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