1A2 Geography

Objectives:• To identify three types of volcano.• To discuss both the positive and negative

effects of volcanic activity.

Homework

• For tomorrow’s class, you must complete question 1, page 79.

1. (i) Name ONE example of a volcano.(ii) With reference to the diagram (pg. 79)

explain how volcanoes occur.

Mid-term Assignment

• Please place your mid-term assignments on your desk so I can collect them.

• Before the mid-term break, you were told that all assignments will be collected today.

• Marks will be deducted for late submission:– 5% Tuesday 23rd.– 10% Monday 2nd.– 20% Tuesday 3rd.Assignments will not be accepted after this date.

Before the mid-term break…

You learned that:• Earth is divided into layers.• The outer layer (crust) consists of plates.• These plates move due to convection currents.• Plates collide, separate and slide past one

another.• Plate movement leads to volcanic activity.How was the Mid-Atlantic Ridge formed?

Three types of volcano

• There are three different kinds of volcano, each classified according to the rate at which volcanic eruptions occur.

1. Active.2. Dormant.3. Extinct.

Active Volcanoes

• Active volcanoes erupt on a regular basis.

• Examples include:Mount Etna, Sicily.Mount St. Helens, USA.• (We will be learning

more about Mount St. Helens during tomorrow’s class.)

Dormant Volcanoes

• Dormant volcanoes have not erupted for a long time, but could potentially erupt again.

• Examples include:Mt. Vesuvius, Italy – you’ve already learned a little about this in History.

Extinct Volcanoes

• Extinct volcanoes have not erupted in recorded history.

• They are unlikely to erupt again.

• Irish examples include:Croghan Hill, Co. Offaly.

Positive effects of volcanoes

• In pairs, identify one way in which a region can benefit from volcanic activity – you have 30 seconds!

Positive effects of volcanoes

• Land Creation: Volcanic activity can lead to the formation of new land which people can farm and live on.

• Fertile Soils: Soils created from lava flows are rich in minerals and are very good for agriculture. Mt. Vesuvius has produced the fertile soils of the Campania region of Italy.

• Tourist Sites: People visit areas with famous volcanoes, e.g. Mount Etna, Sicily.

Positive effects of volcanoes

• Geysers: Magma close to the surface heats water under ground. This leads to the creation of hot springs where jets of water are periodically fired into the air.

• In Iceland, geysers are used to generate geothermal energy.

Negative effects of volcanoes

• In pairs, identify one negative effect of volcanic activity in a region – you have 30 seconds!

Negative effects of volcanoes

• Poisonous Gas: Some gases emitted during eruptions are toxic, e.g. sulphur dioxide. Gases can also create acid rain.

• Loss of Life: People can be killed by a volcanic eruption.

• Damage to Property: Lava burns everything in its path.

Negative effects of volcanoes

• Lahars: Rivers of mud, called lahars, can be created if a volcanic eruption occurs on a snow-capped mountain. Here lava mixes with snow and flows downhill as intensely hot, boiling mud. Lahars have the potential to destroy entire towns and villages. This has happened in Montserrat in the Caribbean.