Earth Hazards Revision –Level 5

1. Map showing where volcanoes and earthquakes happen

                                                                                                      

                          

Mid-Ocean Ridges

Pacific Ring of Fire

MediterraneanMediterranean to Indonesia

Andes Mts

Earthquake lines

Volcanoes

5C Describe and explain the effects of a volcano on nearby villages.

• Dust clouds from the volcano block the sunlight

• So the village gets as dark as nighttime.

• Ash falls all round the volcano

• So houses collapse and roads are blocked to vehicles.

• Lava flows down to the village so homes are buried or burned..

Case study – Italy’s Mt. Etna

5C What is deforestation.

• Deforestation means “cutting down trees”.

The word comes from:-

• De (doing away with)

- forest (area of many trees)

- ation ( the process)

5B Describe and explain why deforestation causes soil erosion.

• Soil erosion means that soil has had most of its cover of trees removed.

• Then the soil is easily blown away by wind or washed away by streams.

This soil has been washed away

leaving a gully

5A Describe and explain why deforestation causes soil erosion.

• A cover of trees usually protects the soil.

• If trees are cut down soil is exposed to rain and wind.

• Rainwater then washes away topsoil into rivers, leaving little valleys (called gullies) in the soil

• Then the extra mud in rivers clogs them up and causes floods.

• Because the sandy subsoil is now exposed, strong winds can blow it away to create sand dunes.)

• Sand dunes can cover valuable farmland.

• The soil left behind is useless

•Because it is soil which is moved the processes are called soil erosion.

5A Why Soil Erosion is a Hazard.

• Because the soil is loose, heavy rain can cause mudflows which cover homes and can kill people.

• Even when rainwater washes away topsoil gently into rivers, the extra mud forms mudbanks.

• Because of this navigation becomes difficult for ships.

• Because of the mudbanks, rivers flood more deeply, destroying more farmland..

• Because sand dunes creep forward in the wind, valuable farmland may be covered and destroyed.