Volcanoes occur at boundaries where tectonic plates meet, such as divergent boundaries where plates move apart or convergent boundaries where they move together, or at hot spots where the Earth's crust is thinner. When two plates are pushed together at a convergent boundary, one plate may be subducted under the other due to its greater density, melting rock and forming magma. Pressure builds as magma rises into the magma chamber until an eruption releases gases and material.
7. Can you put the following sentences in the right order to explain how a volcanic eruption may happen. J) The oceanic plate is subducted underneath the continental plate because it is heavier. I) The pressure is released in a dramatic explosion unleasing millions of tonnes of rock and lava. H) The magma chamber begins to swell as magma rises into the chamber. G) Pyroclastic flows bring rock, steam and ash rushing down the side of the mountain. F) Debris in the crater of the volcano blocks steam and ash and pressure begins to build up. E) Friction between two plates helps to melt the rock. D) Two tectonic plates are pushed together. C) Magma forces it’s way through the rock layers. B) The magma chamber releases steam and gas. A) Small earthquakes felt.
12. 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 Lava Flow Crust Pyroclastic Flow
13. 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
14. Shield ( Basic) Cone Shield Volcanoes are enormous features built 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
15. Kilauea in Hawaii is an example of a shield volcano. Characteristics Wide base Gentle sloping sides Basic (runny lava) Gentle but continuous eruptions
19. 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 ) Economic problems from the cost of rebuilding, loss of farmland, factories ,tourism and other economic activities. Farmland destroyed and livestock (animals) killed. Buildings and property destroyed Social problems from family losses and stress. Communications and infrastructure/public services disrupted. EG; transport, electricity, telephones. Spread of disease from contaminated water. Shortages of drinking water, food and shelter People injured and killed
21. 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 Energy While 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.
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