Volcano

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Volcano

• A vent in the surface of the Earth through which
  magma and associated gases and ash erupt
• Volcanoes can beactive still erupt
  regulartly e.g. mt Etnadormant not erupted for
  a while
• Extinct wont erupt again.

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Areal Distribution of Volcanoes
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Oceanic Volcanoes
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Eruptions

• Magma spews upward with great force through a
  central vent

Left Mt. St. Helens, 1980 Right Kilauea, Hawaii
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• Lava flows can ruin agricultural land or go
  through towns such as on Mount Etna in Italy

Aa
Pahoehoe

• Lava can Flow at different speeds depending on
  how runny the lava is. The two types of lava flow
  above are called Aa and Pahoehoe (from the
  Hawaiian)

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• Mount Pinatubo (Philippines - 1991). Huge amounts
  of ash can be blasted into the atmosphere.

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Ash effects

• Rabaul Town and Harbor after eruption

Rabaul Town and Harbor before eruption
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Effects of Ash (tephra)

• Ash falls on crops killing them. Also falls on
  roofs of houses causing them to collapse under
  the weight
• Large volcanic eruptions can block a great deal
  of the suns energy from reaching the earths
  surface
• This cools the climate until the tephra particles
  sink to the surface
• Ash can get into aeroplane engines and cause them
  to crash
• It can also cause breathing problems

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e.g. Krakatau Volcano

• Location Indonesia
• The eruption killed 33,000 people. Mainly those
  living by the sea who were killed by giant waves
  created by the blast

Effects of Tsunami in Hawaii
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• One of the best examples of lateral blast damage
  is Mount St Helens.
• The blast knocked down a large number of trees
  making the area look as though a giant had
  combed its hair

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• A swiftly flowing hot gaseous cloud, erupted
  from a volcano and containing ash and other
  pyroclastics in its lower part. It can be up to
  10000 C and flow at 100 mph

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• These are lumps of magma thrown out from the
  volcano and which solidify in the air.
• They can be as large as a small car obviously
  creating a bit of a hazard!!

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• Gases such as Carbon Dioxide, Carbon monoxide and
  sulphur dioxide come out of the crater.
• One volcano in Cameroon killed many people and
  animals just from the gas alone.

• The gases mix with rainwater creating acid rain.
• They also mix with water in volcanic lakes
  turning them highly acidic

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• This is the most deadly of the volcanoes forces.
• Mud and water (often from melted snow or
  glaciers) go at huge speeds down volcanoes.

22000 people died in a lahar in Colombia
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• Earthquakes often happen before a volcano erupts.
• This is due to magma rising and creating pressure
  on the rocks causing them to split.

Seismometer reading before eruption
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Qu. 1.What are the 7 main hazards Associated with
Volcanoes
Volcanic Hazards
Qu. 2. Name the two different types of Lava flow,
and say how they are different.
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• Volcanoes present a number of hazards for humans
• Lava Flows
• Earthquakes
• Ash
• Pyroclastic Flows
• Lateral Blasts
• Volcanic Bombs
• Lahars

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So Why do people live near them?

• The main thing is that the ash and lava break
  down to produce fertile soils
• Because of this large numbers of people in the
  developing world live and farm near active
  volcanoes such as the one in Indonesia

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Geothermal Energy

• In places such as Iceland, California and New
  Zealand water is heated up and used to drive
  geothermal energy plants.

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Minerals

• The rocks in many volcanic areas contain valuable
  minerals such as gold and zinc aswell as precious
  stones
• Pumice stones come from volcanoes

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Tourism

• Many volcanic areas attract tourists e.g
• Yellowstone National Park
• Mount Etna
• Mount St Helens
• Places with hot spas such as New Zealand

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Building Materials

• Blocks of lava are used for building materials
• Granite is a volcanic rock
• Ash is used in cement to build with.

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Benefits of Volcanoes Task

• Draw another spider diagram listing with examples
  5 benefits of volcanoes.

Benefits of living in volcanic areas
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Types of Volcano

• Composite Volcano e.g. Mt. Etna. Steep sided,
  layers of acid lava and ash
• Acid Lava Volcano
• Steep sides. Acid lava doesnt flow easily.
  Very explosive
• e.g. Mt Pelee, Martinique.
• Shield Volcano Gentle slopes. Basic lava flows
  easily. Frequent eruptions e.g. Kilalauea,
  Hawaii.

Cross section
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Case Study A Paricutin - Mexico

• A crack opened up in a field one day.
• A volcano grew from this and erupted slowly over
  a long period.
• Eventually the local town was covered with lava.
  E.g. the church on the left

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Case Study B Mt. Vesuvius .. Pompeii

• A famous historical eruption about 2000 year ago.
• The photo below shows people who were encased in
  volcanic ash.

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Case Study C Mt. Pelee. Martinique

• Eruption
• Remains of city.Only 1 person survived

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Case Study D Montserrat - Soufriere Hills

• This is an island in the Caribbean
• The islands main volcano erupted leading to the
  evacuation of the main town of Plymouth.

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• Nevado Del Ruiz is a volcano situated in colombia
• Vulcanologists noticed earthquakes in the region
  on 1985 and warned there might be an eruption.
• The government thought that all was ok and didnt
  evacuate.
• The following night 22,000 people died

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, the National Bureau of Geology and Mines
(INGEOMINAS) declared that a moderate eruption
would produce " . . . a 100 percent probablity of
mudflows . . . with great danger for Armero . . .
Ambalema, and the lower part of the River
Chinchina." However, some government officials
dismissed the report as "too alarming" and
authorities did not want to evacuate people until
they were assurred of the necessity
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What are the benefits of Volcanoes

• Ash and lava break down to provide fertile soil
  e.g indonesia
• They can be used to produce geothermal energy
  e.g. iceland
• Rocks in volcanic areas contain valuable minerals
  e.g. andes mountains
• Volcanic areas such as Hawaii are tourist areas
• They provide building materials

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What to Do about Volcanic Eruptions

• Man cannot stop subduction, or magma generation -
  therefore, the prediction of imminent eruption
  becomes very important.

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• What To Do If a Volcano Erupts
• BEFORE
• Learn about your community warning systems and
  emergency plans.
• Be prepared for the hazards that can accompany
  volcanoes
• Make evacuation plans.
• If you live in a known volcanic hazard area, plan
  a route out and have a backup route in mind.
• Develop an emergency communication plan.
• In case family members are separated from one
  another during a volcanic eruption (a real
  possibility during the day when adults are at
  work and children are at school), have a plan for
  getting back together.
• Ask an out-of-state relative or friend to serve
  as the "family contact," because after a
  disaster, it's often easier to call long
  distance. Make sure everyone knows the name,
  address, and phone number of the contact person.
• Have disaster supplies on hand
• Flashlight and extra batteries
• First aid kit and manual
• Emergency food and water
• Non-electric can opener
• Essential medicines
• Dust mask
• Sturdy shoes
• Get a pair of goggles and a throw-away breathing
  mask for each member of the household in case of
  ashfall.