Volcanoes Revision

Basic structure of Volcano

• There are 3 main types of volcano:

• Acid Lava DomeEg: Puy de Dome• Basic Lava ShieldEg: Mauna Loa

Hawaii • Composite cone /

Ash coneEg: Pinatubo -

Phillipines

Three types ….

• There are 3 main types of volcano:• Acid Lava DomeEg: Puy de Dome• Basic Lava ShieldEg: Mauna Loa Hawaii • Composite cone / Ash coneEg: Pinatubo - Phillipines

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Magma Chamber

Vent

Secondary Vent

Layers of Ash & Lava

CraterAsh Cloud

Pyroclasts

Pryoclastic Flow

Lava Flow

A Composite Cone

Three types … Dome (Acid Lava Cones)

• Acid [lava] is much thicker than [lava] which flows from shield volcanoes.

• Dome volcanoes have much steeper sides than shield volcanoes.

• This is because the lava is thick and sticky. It cannot flow very far before ot cools and hardens.

• An example is Puy de Dome in the Auvergne region of France which last erupted over 1 million years ago.

Puy de Dome

Steep sides

Rounded summit

Short diameter at

the base Extinct crater

Three types … Shield

• Shield volcanoes have gently sloping sides and are formed from layers of lava.

• Eruptions are typically non-explosive. • Shield volcanoes produce fast flowing fluid

[lava] that can flow for many miles.• Examples of shield volcanoes include the

Hawaiian volcanoes. • Although these eruptions destroy property,

death or injury to humans rarely occurs.

Three types … ShieldMauna Loa, near the center of

Hawaii, is the central part of a huge shield volcano, which comprises the entire island. Its summit crater, lies beneath a crest at 4,135 m (13,563 ft). Its base lies about 4,000 m (13,120 ft) below sea level, which makes it the tallest single mountain in the world Mauna Kea, a crater on the north section of the island, is now extinct. But the most active volcano in the world, Kilauea, lies along the east side of the island and is visible here as a dark patch.

Mauna Loa

Mauna Kea

Kilauea

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Three types … Composite

Composite cone or Strato volcano

Volcanic Hazards• Lava Flows – rarely kill people, but destroy land and settlement

• Ash fall – buries crops and housing. Many years before the fertility of the ash is useful.

• Pyroclastic flow / Glowing Cloud / Nuee ardent – clouds of gas and ash of 1200 deg. C travelling at speeds up to 200km/h

• Lahar / Mud flows – Ash flows liquidised by heavy tropical rain or melting snow & ice. These travel at great speed and bury land and settlement to great depths.

• Poisonous gases – Carbon Monoxide, Sulphur dioxide kill animals and people

• Destruction of buildings • Loss of life • Destruction of farmland • Fires • Economic losses

A comparison of the damage done by these tectonic hazards in urban and rural areas

• urban areas have a higher density of people and buildings than rural areas, and thus usually suffer more loss of life and a higher economic cost

• bridges collapse, the economy is affected

A comparison of the effects of tectonic hazards in MEDCs and LEDCs

• MEDCs cope better with natural disasters because:

• they have better monitoring equipment to predict impending disasters

• of stricter building controls • of more effective relief measure • of better infrastructure

• there is access to trauma counselling

Volcanic advantages• Fertile land – eventually after many years of

weathering of the ash falls.

• Geothermal Power – in some areas this provides electricity and hot water. Eg: Iceland

• Creates new land – lava flows reaching the sea build up the land Eg: Hawaii and Heimaey(Iceland).

• Tourism – often provide a tourist attraction if the volcano is not explosive. Eg: Mauna Loa, Hawaii; Vesuvius, Italy.

• Health – hot ash and highly mineralised water used by health spas Eg: Japan.

• Mineral Wealth – Eg: Sulphur deposits.

Protection from future tectonic hazards

• Preparation – in anticipation of tectonic hazards

• Prediction – to allow for evacuation