volcanoes and volcanic activity
DESCRIPTION
Slides on how volcanoes are formed, the main features of a volcano, effects of a volcanoTRANSCRIPT
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Volcanic Activity
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• 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
Volcanic Activity
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The Mid Atlantic Ridge
Under the Atlantic Ocean lies a long, narrow chain of mountains called the Mid Atlantic Ridge.
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Mid Atlantic Ridge was formed when plates separated and lava came to the surface and cooled and hardened.
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Iceland
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Mid Atlantic Ridge In Iceland
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The Pacific Ring of Fire.
Most earthquakes and volcanoes
occur along this line.
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Volcanoes – Good and Bad
Benefits Drawbacks
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• A volcano is a cone-shaped mountain or hill, formed by eruptions of lava and ash.
• When magma reaches the Earth's surface it is called lava. When the lava cools, it forms rock.
• Volcanic eruptions can happen at destructive and constructive boundaries, but not at conservative boundaries.
• Some volcanoes happen underwater, along the sea bed or ocean floor.
Volcanic eruptions
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• Magma rises through cracks or weaknesses in the Earth's crust.
• Pressure builds up inside the Earth.
• When this pressure is released, magma explodes to the surface causing a volcanic eruption.
• The lava from the eruption cools to form new crust.
• Over time, after several eruptions, the rock builds up and a volcano forms.
•
How volcanoes form
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A volcano has several important features:
• The magma chamber is a collection 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.
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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)
Different types of Volcanoes.
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2012 Junior Cert
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