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ClickView playlist To login use your student number & email as your username: studentnumber@oxley.nsw.edu.au
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Volcano facts
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Britannica volcano information Your password is your Oxley student number
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Types of volcanoes
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About volcanoes
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Health effects of Volcanoes
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Eruption styles
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What is a volcano?
A volcano is a vent in the Earth's crust which transfers molten rock (magma) from depth to the Earth's surface through eruptions. Magma which remains molten once reaching the Earth’s surface is called lava. Volcanic eruptions can also produce tephra (fragments of solid rock and magma, including volcanic ash). Tephra and lava build up around the vent and form a cone.
A volcano is classed as active if it has erupted within the last 10 000 years, and active volcanoes can be erupting, dormant or in a phase of unrest. A volcano is erupting if it is producing tephra or lava, it is dormant if it is not erupting but has the potential to erupt in the future. Unrest is a transitional phase where a volcano shows increased signs of activity (seismic activity, releasing gas). When a volcano has been dormant for more than 10 000 years, it is considered extinct. Volcanoes can remain inactive, or dormant, for hundreds or thousands of years before erupting again. During this time, they can become covered by vegetation, making them difficult to identify.
How explosive a volcanic eruption is depends on how easily magma can flow or trap gas. If magma is viscous, it is able to trap a large amount of gas and can produce explosive eruptions.
Volcanoes can have many different appearances. Some volcanoes are perfect cone shapes while others are deep depressions filled with water. The shape of a volcano provides clues to the type and size of eruption that occurred. Eruption types and sizes depend on what the magma is made up of.
