chapter 1 – the restless earth

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What does the Earth have in common with an Onion?

A.They both taste niceB.NothingC.They both have layers

1. The inner core is in the centre of the earth and is the hottest part of the earth. The inner core is solid. It is made up of iron and nickel with temperatures of up to 5500°C. With its immense heat energy, the inner core is like the engine room of the Earth.

•2. The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot here, with temperatures similar to the inner core.

This spinning liquid layer creates a magnetic field and makes compasses point towards the North Pole

•3 The mantle is the widest section of the earth. It has a diameter of approximately 2900km.

The mantle is made up of semi-molten rock called magma.

In the upper parts of the mantle the rock is hard, but lower down, nearer the inner core, the rock is soft and beginning to melt.

•4. The crust is the outer layer of the earth. It is a thin layer between 0-60km thick. The crust is the solid rock layer upon which we live.

There are two different types of crust: continental crust, which carries land, and oceanic crust, which carries water.

The Earth’s Crust is broken up into different sections called Plates – think of an egg with a cracked shell

The Plates float on top of the liquid magma in the Mantle and are pushed around by convection currents in the magma

Plate boundaries are the lines where two plates meet

The Earth’s Plates – which one is Ireland on?Iceland is on the border of which two plates?

Boundary of two plates in Iceland

Heat rising from the hot core causes convection currents which pull crustal plates apart.

Plates behave differently at different plate boundaries:

At a constructive or divergent boundary the plates move apart.

At a destructive or convergent boundary the plates move towards each other.

At a conservative or transform boundary the plates slide past each other.

Convection currents in mantle.

Plate BPlate A

Lava, Gas, Steam.

Plates colliding.

Plates colliding with each other can cause earthquakes, volcanoes and fold mountains

Plates separating can cause mid ocean ridges, volcanoes and new land to be formed. Very few earthquakes here

Plates scraping past each other can cause earthquakes

When plates collide with each other, the pressure becomes so great that the earth’s crust becomes buckled and arches upwards, forming Fold Mountains.

Some Fold Mountains include the Alps, the Rocky Mountains and the Andes.

These were formed during the Alpine foldings about 35 million years ago.

Equal pressure from both sides

SIMPLE SYMMETRICAL FOLDSBoth limbs of the fold dipping at same angle

Our youngest Fold Mountains were formed during the Armorican Foldings about 250 million years ago!! These are found in Munster, the Macgillicuddy Reeks.

2011 Ordinary Level Paper

This mountain has been folded up at a rate of 4 millimetres a year!What does that tell us about the process of mountain building?

2011 Junior Cert

The innermost part of the Earth is known as the Inner Bore Slabs of the Earth’s Crust that float on the Mantle are known

as Plates The outer core is made of hot molten metal When plates collide mid ocean ridges can form Earthquakes can happen when plates separate Mount Everest is a fold mountain The McGillycuddy’s Reeks were formed during the Armorican

foldings The inner core is made of Hot Solid Metal

An earthquake is the shaking and vibration of the crust due to movement of the Earth's plates (plate tectonics) Earthquakes are most common where plates collide or scrape past each other

Two plates try to slowly slide past each other but get stuck

Pressure builds up...and up....AND UP Eventually the pressure gets so great that the plates

break free and all the pent up energy is released as an Earthquake

An earthquake under the sea can cause a tidal wave called a Tsunami

Fault – border between two plates

Focus – where the earthquake happens, deep underground

Epicentre – point directly above the focus, on the surface. Earthquake is strongest here

Buildings damaged or destroyed Roads/railways damaged Broken water/sewer/electricity lines People killed Fires (when gas/petrol pipes break)

Earthquake damage can be reduced by using springs the foundations of tall buildings

These are caused when a huge section of seafloor rises up during an earthquake

A huge amount of water is pushed outwards – when it reaches land it rushes in as a massive wave

Japanese Tsunami, 2011

2011 Junior Cert

The power of an earthquake is measured using a seismometer. A seismometer is a sensitive machine, which picks up the vibrations caused by the earthquake. It plots these vibrations on a seismograph.

The strength, or magnitude, of an earthquake is measured using a scale called the Richter Scale. The Richter Scale is numbered 0-10:

Volcanoes form when magma reaches the Earth's surface, causing eruptions of lava and ash. They occur at destructive and constructive plate boundaries

Magma – Molten Rock Underground Lava – molten rock on Land

Pressure builds up inside the Earth

The magma forces its way towards the surface.

When pressure has built up enough, magma explodes to the surface causing a volcanic eruption.

The lava (magma on the surface) from the eruption cools to form new crust.

Over time, after several eruptions, the rock builds up and a volcano forms.

A volcano has several important features:

The magma chamber is a store of magma inside the Earth, below the volcano.

The main vent is the main outlet for the magma to escape. Secondary vents are smaller outlets through which magma

escapes. The crater is created after an eruption blows the top off

the volcano.

One way to describe volcanoes is in terms of activity: Some volcanoes are still active and erupt frequently

(Etna and Vesuvius Italy) Some volcanoes are dormant (sleeping). (Cotopaxi,

Peru) Some volcanoes are extinct (never likely to erupt

again). (Slemish, Co.Antrim)

Hot ash and gas in a volcanic eruption

Lava being forced to the Earth’s surface in a volcanic eruption

Pompeii – bodies preserved by volcanic ash from an Eruption

Most earthquakes and volcanoes

occur along this line.

2005 Higher Level Paper

2010 Higher Level Paper