Earthquakes:

•  An earthquake is a series of seismic waves or tremors in the earth’s crust.
•  They usually occur along the edge of plate boundaries in areas called fault lines.
•  They are caused when pressure builds up at the edge of the plates as they collide or slide past one another.
• When this pressure is released a huge amount of energy is released causing the plates to shake. This shaking movement is the earthquake.
• The Earthquake occurs in the place where the plates collide.

• Tremors are the waves of seismic energy which spread out from the Focus.
•  Aftershocks are the smaller tremors which may occur hours or days after the original earthquakes. They can also be extremely dangerous because they may cause already damaged buildings to collapse.
•  The Focus is the place deep in the earth’s crust where the earthquake begins.
• The Epicentre is the place on the surface of the earth, directly above the Focus. The tremors are strongest at this point.

•  The strength or force of an earthquake is measured on a Seismograph.
• The scale used to describe this force is called the Richter Scale. This scale ranges from 1- 12.
•  People are still unable to predict when earthquakes will occur, but we can predict where the plates meet and could cause an earthquake.
• Earthquakes can also occur at sea and produce giant waves called tsunamis e.g. Asian tsunami, 26th December 2004.

Volcanoes:

• Volcanoes occur when hot molten lava forces its way to the surface through a narrow channel in the earth’s crust called a vent.
• These vents are usually found at plate boundaries.
• When the hot molten rock reaches the surface it is known as lava.
•  The process of the lava reaching the surface is called an eruption.
•  Volcanoes can be classified as being either active, dormant or extinct
• Active: The volcano erupts regularly.
• Dormant: The volcano has not erupted for a long period.
• Extinct: The volcano has not erupted in a long time and is unlikely that it will ever erupt again.

Pacific Ring of Fire: An area around the Pacific ocean where around two thirds of the world’s volcanoes are located.

Constructive Effects of Volcanoes:

• The soil produced by lava can be fertile and can help the growth of crops.
• The heat from volcanoes can be used to create energy e.g. In Iceland
• New land can be created e.g. Surtsey off the coast of Iceland
• Are often tourist attractions which are beneficial to the local economy.

Destructive effects of Volcanoes:

• Loss of life.
• Damage to property and infrastructure.
• Poisonous gasses which are often released during eruption.

Fold Mountains

• Fold Mountains are formed when the plates of the earth’s crust collide and the crust buckles up.
• The upfolds form the mountain and are called anticlines and the downfolds are called synclines.
• Nearly all major mountain ranges have been formed this way.
•  Mountain building periods:
  • The Caledonian mountains were formed about 400 million Years ago e.g. Mountains of Donegal.
  •  Armorican mountains were formed about 250 million years ago e.g. Macgillycuddy reeks in South of Ireland.
  • The Alpine Mountains were formed about 35 million years ago and are the highest in the world. Eg Alps, Himalayas.

Effects of mountains:

•  They act as barriers between people.
• They can affect the climate of a region by making a region colder due to their height or by cutting off rain-bearing winds.
• They can be suitable locations for coniferous forests.
• They can be used as land to graze animals such as sheep
• They can provide suitable sites for hydro-electric plants.
• Become areas visited by hill walkers and tourists.