CTYI – Spring Session

Volcanoes, Earthquakes and Tsunamis

Hey guys, so I have made this booklet, so you can have access to notes from classes 1 to 6.

Lesson One – The Big Bang and the Formation of Earth

Our universe is 13.8-billion-years-old. So, as you can imagine, it is extremely difficult to know what really happened at the beginning but using science we have a pretty good idea. Scientists believed an event called the ‘Big Bang’ marked the beginning of our universe.

What is the big bang?

About 14 billion years ago our entire universe was thousands of times smaller than the top of a needle. It was extremely hot and dense. All of a sudden it exploded. In a fraction of a second, they universe grew larger than a galaxy, and is still growing today. As the universe expanded a lot happened – it began to cool down and particles began to form. These particles went on to make hydrogen and helium – two gases that are still found on earth today!

How did the Planets form?

Around 4.6 billion years ago, the solar system was just a cloud of dust and gas known as the solar nebula. The sun formed in the centre of the nebula when gravity squashed the particles together and it began to spin. After the sun was formed, the remaining particles began to stick together – so now the solar system is made up of the sun in the middle, and a collection of small particles and larger particles. The larger and heavier particles were pulled together by gravity and the smaller rocky planets (like Earth) were formed. The smaller and lighter particles were carried further away, and they then formed the gas giants (like Venus).

Earth – Earth’s rocky core formed first. The heavy particles got pulled into the centre, while the lighter particles created the crust. These particles began to spin. As it spun, the material squashed together and compressed to form the Earth we know today.

Early in its formation, Earth suffered an impact by a large body that sent pieces of young earth into space. Gravity caused these pieces to pull together and form our moon.

What is the structure of the earth?

The Core: The core is the very hot, very dense centre of our planet. It is made up of the inner core and the outer core.

Stiffer Mantle: This is the thickest part of the Earth and lies above the core.

Asthenosphere: This is the very slow-moving region of the upper mantle. Closer to the surface, the mantle is solid, while deeper below

the surface the mantle has some movement.

Lithosphere: This is the hard and rigid layer, made up of the rigid mantle and the crust.

The Crust: The crust is composed of the oceanic crust and the continental crust.

Lesson Two – Plate Tectonics

The lithosphere is divided into a patchwork of large tectonic plates, that move around. Each plate moves at different speeds and in different directions. There are 7-8 major plates that make up the lithosphere, and many smaller ones. As the plates move around, they carry the continents with them.

As the plates move about, they tend to bump into each other or pull away from each other.

How do the plates move?

Mantle Convection – This is the process in which heat from Earth’s interior is transported to the surface. As cool mantle sinks down closer to the core, it begins to melt. This hot magma is forced up towards the surface of the earth, where it cools. This cycle of cooling and then reheating of the mantle creates a current, which results in the movement of the tectonic plates.

There are three types of plate boundaries.

Divergent Plate Boundaries:

This is a tectonic plate boundary where two plates are moving away from each other. As the plates move away from each other a new crust is formed from the magma that rises to the Earth’s surface. This can lead to the formation of mountain ranges.

Convergent Plate Boundaries-

This is a tectonic plate boundary where to plates move towards each other and collide. Two things can happen here, if two of the same type of plate push up against each other (a continental plate and a continental plate) they can form a mountain range. If two different types of plate (a continental plate and an oceanic plate) push up against each other, the oceanic plate will get pushed below the continental plate and this will form a trench.

Transform Plate Boundaries:

This tectonic plate boundary occurs when two plates slide past one another. These boundaries are harder to identify, as they don’t form magnificent features on the earth’s surface. However, the sliding motion causes a lot of earthquakes.

Lesson Three – Volcanoes

What is a volcano?

A volcano is a rupture in the crust of the earth that allows hot lava, volcanic ash and gas to escape from a magma chamber below the surface.

How are they formed?

Convergent Plates: When a continental plate and an oceanic plate collide, the oceanic plate is forced beneath the continental plate in a process known as subduction. As the plate melts, it creates new magma, which is forced to the surface and erupts out of the crust.

Divergent Plates: As two plates move apart, it creates a gap that allows magma to rise up, creating new crust. Long chains of volcanic mountains form along divergent plate boundaries.

Hot spots: A hot spot is an area of Earth’s crust that lies over an extremely hot area of magma. The heat of the magma causes the crust to melt. As the crust melts, the magma forces its way to the surface and creates a volcano.

Types of Volcanos

Composite Volcano

Also called a stratovolcano. These volcanos are formed when many layers of lava and ash build up a tall peak. These volcanos are formed by thick slow-moving lava.

Shield Volcano

A shield volcano is a wild volcano with sloping slides. The are formed by extremely fluid lava. When the volcano erupts the lava spreads over a large distance.

Caldera

A caldera forms when a volcano erupts and collapses. This only occurs with extremely explosive volcanic eruptions.

Lesson Four – Earthquakes

What is an earthquake?

An earthquake is a sudden violent shaking of the earth, typically causing great destruction, as a result of movements within the earth’s crust of volcanic action

Why do they happen?

1. Volcanic Erruptions: The main cause of earthquakes is volcanic eruptions. When boiling magma tries to break through the surface of the earth, it causes movements of the earth’s crust. These movements can send out shockwaves, which cause earthquakes.

2. Tectonic Movements: Earthquakes occur at all types of plate boundaries. The movement of the tectonic plates in the lithosphere can be sudden. Any sudden movements of the earths crust can result in earthquakes. Earthquakes are most common at Transform Plate Boundaries, where two plates slide past each other.

3. Man-Made: Us humans can cause earthquakes. Mining and bombs can trigger shockwaves in the earths surface.

4. Minor Causes: Landslides and avalanches can also cause minor shockwaves.

How do we measure them?

When an earthquake hits, seismic waves radiate out from the focus. As these energy waves travel through the earth’s surface, they can cause serious damage on the surface.

We can measure Earthquakes using a Seismograph. Originally, they consisted of weighted swing attached to a solid base, as shown in the picture below. During an earthquake, a seismograph records the seismic waves that travel through the earth. Modern seismographs are electronic.

An earthquake recorded by a seismograph typically looks like this.

As we can see on this graph there are two types of waves.

P waves: These are the Primary Waves. These waves travel in a straight line through the earth’s crust. They are the first waves that get picked up by a seismograph.

S waves: These are the secondary waves. They move like a wave through the earth’s crust and travel slower than a P wave. These waves cause the most damage on the earth’s surface.

Lesson Five – Tsunamis

What is a Tsunami?

A tsunami is a series of ocean waves that send surges of water, sometimes reaching heights over a 100ft. onto land.

Why do they happen?

A tsunami is typically caused by large undersea earthquakes, but they can also occur as a result of underwater landslides or volcanic eruptions.

When the ocean floor at a plate boundary rises or falls suddenly, it displaces the water above it and send rolling waves that will become a tsunami. The same occurs with a landslide or volcanic eruption. The force of the movement causes the displacement of water, and creates rolling waves.

Tsunami Facts:

Tsunamis race across the sea as fast as a jet plane, up to 800km an hour. They can travel the entire length of the Pacific Ocean in less than a day.

In deep ocean, tsunami waves may appear only a foot or so high. When they hit shallow water, they grow in energy and height.

A tsunami is usually composed of a series of waves, that can range anywhere between 5m and 1h apart.

Tsunamis can travel as far as 16km inland destroying anything in their path.

Scientists believe that 3.5 billion years ago, an asteroid hit the earth which would have caused a tsunami wave so large that it travels around the earth 3 times – covering everything except the highest peaks.

Lesson Six - Experiment Day

I have attached some links for the methods we used in class. Please make sure to ask parents permission first, if you wish to do any of these again. It can get messy!

Volcano:

http://www.sciencefun.org/kidszone/experiments/how-to-make-a-volcano/

Earthquake

http://fallingintofirst.com/2013/04/shakin-quakin-earthquake-showdown/

Tsunami

https://www.youtube.com/watch?v=DZZFPCY6RlE

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