Where do volcanoes occur?

• They often occur when Earth’s tectonic plates:– Move apart – divergent boundary– Move towards each other – convergent

boundary– At “Hot Spots” – where crust of Earth is

thinner than normal

This distribution of volcanoes is called the RING OF FIRE as they form a circle around the edge of the Pacific plate.

Constructive Plate Boundary

Destructive Plate Boundary

Where does magma form?

Can you put the following sentences in the right order to explain how a volcanic

eruption may happen.

A) Small earthquakes felt.

B) The magma chamber releases steam and gas.

C) Magma forces it’s way through the rock layers.

D) Two tectonic plates are pushed together.

E) Friction between two plates helps to melt the rock.

F) Debris in the crater of the volcano blocks steam and ash and pressure begins to build up.

G) Pyroclastic flows bring rock, steam and ash rushing down the side of the mountain.

H) The magma chamber begins to swell as magma rises into the chamber.

I) The pressure is released in a dramatic explosion unleasing millions of tonnes of rock and lava.

J) The oceanic plate is subducted underneath the continental plate because it is heavier.

Parts of a Volcano.

D

Volcanic bombs, ash, lava, gases

Magma chamber

Parasitic cone

Crater

Main vent

C

BA

E

Match up the part with the right letter on the cross section of a volcano

Crater Volcanic bombs, ash and gases

Main vent

Parasitic cone

Magma chamber

Cross section of a volcano

VolcanoesVolcanoes

Not just one type

Composite Cone

The volcano is built up of alternate layers of LAVA and ASH. They can explode with great violence.

Montserrat, Caribbean

Conelet

Dyke

Crater

Ash layer

Lava Layer Flank eruption

LavaFlow

Crust

Pyroclastic Flow

Mt St Helens, USA is an example of a composite cone volcano.

Characteristics

Steep sides and narrow base

Violent eruptions

Acidic (sticky) lava, ash, gas, pyroclastic flows, volcanic bombs

Shield ( Basic) Cone

Shield Volcanoes are enormous featuresbuilt up only from layers of lava. They produce lots of lava but they tent not to erupt violently.

Mauna Loa Hawaii -USA

250 miles

10,000m

Composite volcano to scale

Layers of Lava Lava Flow

Kilauea in Hawaii is an example of a shield volcano.

Characteristics

Wide base

Gentle sloping sides

Basic (runny lava)

Gentle but continuous eruptions

Hazards from

Eruptions

• Lava Flows• Ash, rock,

chemicals in the air (acid rain)

• Pyroclastic FLows

• Mud Flows/ Lahars

• Volcanic Bombs

Volcanic Hazards – Can you name the hazards below?

• Pyroclastic flow – hot volcanic gas and ash moving in a cloud directly over the Earth’s surface

• Acid rain – results when sulfur gases from volcano mix w/ water in the atmosphere– Harmful to vegetation and aquatic life

Volcanic eruptions have several effects – Can you sort the following effects out into the two

categories below:Primary effect Secondary effect(immediate impact) (medium & long term after

effects)People injured and killed

Shortages of drinking water, food and shelter

Spread of disease from contaminated water.

Communications and infrastructure/public services disrupted. EG; transport, electricity, telephones.

Social problems from family losses and stress.

Buildings and property destroyed

Farmland destroyed and livestock (animals) killed.

Economic problems from the cost of rebuilding, loss of farmland, factories ,tourism and other economic activities.

Benefits of living in Volcanic Areas

Fertile volcanic soils

The physical breakdown and chemical weathering of volcanic rocks have formed very fertile soils which are excellent for farming and growing crops.

Volcanic rocks

Most of the metallic minerals mined in the world, such as copper, gold, silver, lead, and zinc, are associated with magma. Other rocks/minerals/clays are used in building, cosmetics and as abrasives such as pumice.

Tourism

Hot springs are found in volcanic areas so spas and resorts grow up to make use of them. Also attractive mountainous terrain of volcanic areas are also attractive sites for hiking, camping, and climbing as well as viewing the various types of volcanic activities seen at the surface.

Geothermal EnergyWhile Iceland's geology is unique, so is the way the people of Iceland have put this geology to work. Pollution-free geothermal energy heats 87% of the homes in Iceland, including all of Reykjavík, the capital city.