Chapter 4 - Volcanoes Flashcards
Define volcano.
Volcanoes are openings or cracks in the earth’s crust through which magma, ash, cinder and gas pour or erupt. Volcanoes are formed when plates collide or separate. Cracks or vents occur in the crust, through which magma erupts. These often from cone-shaped volcanoes.
What is magma?
Molten rock of great heat in the mantle.
What is lava?
Magma which has reached the crust and cooled in the air quickly.
Where do volcanoes occur?
When two plates collide or separate and cracks or vents occur in the crust.
List three different landforms made as a result of volcanic activity.
Volcanoes, islands and mid-ocean ridges.
What is a mid-ocean ridge?
Magma seeping through cracks in the crust (that were caused by sea floor spreading) and forming volcanic mountains under the water.
Name one mid-ocean ridge and explain how it was made.
The Mid-Atlantic Ridge was formed because the North American and Eurasian plates are separating (sea floor spreading). Magma from the mantle is seeping through and forming underwater volcanic mountains, which in turn over time form volcanic islands like Iceland.
Iceland is a volcanic island. Explain three ways in which Iceland benefits from volcanic activity.
Geothermal springs (heating), geysers (to generate electricity) and new land is constantly being formed.
Volcanoes can be active, dormant or extinct. Explain the difference between these words.
Active: A volcano that’s currently in a state of regular eruptions. Maybe it’s erupting right now, or had an event in the last few decades. Geologists expect it to erupt again very soon.
Dormant: A volcano that is capable of erupting, and will probably erupt again in the future, but it hasn’t had an eruption for a very long time.
Extinct: A volcano that has been cut off from its magma supply, and will never erupt again. Usually hasn’t erupted in the past 10,000 years.
Give four advantages of volcanic activity.
- Fertile soils are created from the backdown of lava, e.g. Mt Vesuvius in Italy.
- Geothermal springs provide hot water and central heating, e.g. Iceland.
- New land is formed, e.g. Surtsey, off Iceland, and Hawaii.
- Tourist visit volcanoes or towns destroyed by volcanoes, e.g. Pompeii; or distinctive landscapes created by volcanoes, e.g. Giant’s Causeway, Co. Antrim.
Give four disadvantages of volcanic activity.
- Many people are killed and towns and cities are destroyed, e.g. Pompeii.
- Farming land is destroyed.
- Lahars - great rivers of mud - can cause great damage.
- Icelandic ash cloud - disruption of air travel.
Name two examples of past volcanic action in Ireland.
Giant’s Causeway and the Antrim Plateau.
