Post on 16-May-2015
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.