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Questions and Answers
What is the main reason why an explosive eruption occurs?
What is the key difference between an active volcano and an inactive volcano?
What type of volcanic eruption is referred to as a 'glowing avalanche'?
Which of the following is NOT a characteristic of an inactive volcano?
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What is the main reason a fissure or quiet eruption occurs?
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Which of the following is a characteristic of an extinct volcano?
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What causes volcanoes to form?
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Which of the following is NOT a type of volcano classified according to structure and composition?
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What is the defining characteristic of a cinder cone volcano?
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Which type of volcano has the steepest slope?
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What is the primary composition of a shield volcano?
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Which areas are most likely to have active volcanoes?
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Study Notes
Classification of Volcanic Eruptions
- Explosive eruptions occur due to buildup of gas under viscous, slow-flowing magma, resulting in violent and rapid eruptions that spew volcanic material, lava, and ash over a large area
- Fissure or quiet eruptions emit lava from a fracture or fissure, with low-viscosity lava allowing gas to escape easily
Classification of Volcanoes by Intensity of Eruption
- Central or explosive eruptions: buildup of gas under viscous magma leads to violent eruptions
- Fissure or quiet eruptions: lava emitted from a fracture or fissure with low-viscosity magma
Classification of Volcanoes by Periodicity of Eruption
- Active volcanoes: regularly erupting or with recent activity, showing signs of gas emission and seismic activity
- Inactive (dormant) volcanoes: capable of erupting again, but with no recent activity
- Extinct volcanoes: unlikely to erupt again, with no lava supply and far from active geologic hotspots
Features of Active and Inactive Volcanoes
Active Volcanoes
- Regular seismic activities
- Acid gases and vapor emission
- Hot springs
- Geysers
Inactive Volcanoes
- Reduced size
- Obliterated cone
- Shut-off magma chamber
- Vegetation
Volcanic Eruptions
- A volcanic eruption is a dangerous and disastrous natural phenomenon that sends out ash clouds, lava, and volcanic bombs
- High risk of danger comes from moving lava, which can cause damage to property and human life
- Volcanic eruptions can be classified by shape, size, lava flows, and discharged materials
- The most dangerous type of eruption is a "glowing avalanche" of hot pyroclastic flows
Types of Volcanoes
- Volcanoes are openings in the Earth's crust where lava, ash, and hot gases flow or eject during an eruption
- Volcanoes can form where there is a way for magma to flow out towards the surface of the Earth
- Volcanoes are commonly found along plate boundaries, areas with thin crust, and above hotspots
Classification of Volcanoes by Structure and Composition
- Composite (strato) volcano: cone-shaped with layers of hardened lava, tephra, pumice, and volcanic ash
- Cinder cone volcano: steep conical hill of tephra that accumulates around the vent
- Shield volcano: built entirely or mostly from fluid lava flows
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Description
Learn about the different types of volcanoes, which are openings in the earth's crust where lava, ash, and gases flow during eruptions. Understand how volcanoes form and the causes behind their eruption.
