Where do volcanoes occur? <ul><li>They often occur when Earth’s tectonic plates: </li></ul><ul><ul><li>Move apart – divergent boundary </li></ul></ul><ul><ul><li>Move towards each other – convergent boundary </li></ul></ul><ul><ul><li>At “Hot Spots” – where crust of Earth is thinner than normal </li></ul></ul>
This distribution of volcanoes is called the RING OF FIRE as they form a circle around the edge of the Pacific plate.
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.
Match up the part with the right letter on the cross section of a volcano D <ul><li>Volcanic bombs, ash, lava, gases </li></ul><ul><li>Magma chamber </li></ul><ul><li>Parasitic cone </li></ul><ul><li>Crater </li></ul><ul><li>Main vent </li></ul>C B A E
Cross section of a volcano Crater Volcanic bombs, ash and gases Main vent Parasitic cone Magma chamber
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
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 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
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 <ul><li>Lava Flows </li></ul><ul><li>Ash, rock, chemicals in the air (acid rain) </li></ul><ul><li>Pyroclastic FLows </li></ul><ul><li>Mud Flows/ Lahars </li></ul><ul><li>Volcanic Bombs </li></ul>
Volcanic Hazards – Can you name the hazards below?
<ul><li>Pyroclastic flow – hot volcanic gas and ash moving in a cloud directly over the Earth’s surface </li></ul><ul><li>Acid rain – results when sulfur gases from volcano mix w/ water in the atmosphere </li></ul><ul><ul><li>Harmful to vegetation and aquatic life </li></ul></ul>
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
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.