Volcanic Landforms

Volcanic Landforms

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• What is a volcano?
• Where do volcanoes occur?
• Positives and Negatives of Volcanoes
• Types and Examples of Volcanic Landform

What is a volcano?

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• A volcano is an opening in the crust of the Earth which allows molten rock to build up forming a variety of structures, most commonly a mountainous landform.

Where do volcanoes occur?

• Volcanoes form at 3 different locations:
• Destructive plate margins - where subducted crust melts and rises to the surface.
• Constructive plate margins - where magma rises through gaps between plates.
• Hotspots - where the mantle is unusually hot, causing chains of volcanoes to form.
• The Pacific Ring of Fire in particular is home to many volcanoes.
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Positives and Negatives of Volcanoes

• Positives
• Geothermal Energy
• Tourism
• Fertile Soils
• New Land
• Minerals
• Negatives
• Destruction
• Poisonous/Burning Gasses
• Ash Clouds
• Lahars (mudflow)

Types of Volcano: Cinder Cone

• A cinder cone is the simplest form of volcano.
• Cinder cones are typically round in shape and are composed of layers of cooled lava.
• Cinder cone eruptions are usually more violent in nature and there is often gas built up in the vent.
• Example: Paricutin, Mexico
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• Caption: Crater of Paricutin, Mexico

Types of Volcano: Shield Volcano

• Shield volcanoes form from basic lava which has a low silica content and is quite runny in nature.
• Because the lava is runny, it spreads out before solidifying.
• Shield volcanoes typically have a wide base and gentle slopes to their peak.
• Example: Mauna Loa, Hawaii
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• Caption: Haleakala, Hawaii

Types of Volcano: Stratovolcano

• A stratovolcano is a large volcano which is composed of layers of cooled and hardened lava, ash, and tephra (rock fragments).
• Stratovolcanoes usually have steep sides, unlike shield volcanoes and have very explosive eruptions.
• Example: Mount St. Helen's USA
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• Caption: Mount St. Helen's USA

Types of Volcano: Caldera

• A caldera is a volcano which has collapsed in on itself, this usually happens when the magma chamber of the volcano is emptied. This can also occur when there is a particularly violent eruption which causes the volcano to lose support.
• Calderas, particularly older ones, quite often contain lakes in their depressions.
• Example: Crater Lake, Oregon, USA.
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• Caption: Crater Lake, Oregon, USA

Types of Volcanic Landform: Lava Tubes

• Lava tubes typically form from pahoehoe (basic) lava, which is runny.
• Runny lava tends to cool very quickly in comparison to acidic lava; when there is a flow of this lava under the surface, its edges can cool and harden while the lava is still flowing.
• This process creates a straw-like cave, some of which are large in nature.
• Lava tubes are only found under the surface of the Earth as when basic lava runs on the surface, it typically moves in a fanned out pattern.
• Example: Valentine Cave in Lava Beds National Monument, California.

Types of Volcanic Landform: Geysers

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• A geyser is a hot spring heated by geothermal energy.
• Geysers are typically found in volcanic areas and are often tourist attractions.
• As water is heated, it expands and pressure builds under the surface. The eruption of a geyser acts as a release of pressure for this water.
• Example: Old Faithful, USA.