Volcanoes Part 2 1 of 35 Boardworks Ltd

Volcanoes – Part 2 1 of 35 © Boardworks Ltd 2006

Learning objectives What is a volcano? Why do volcanoes occur? Where are volcanoes found? Can volcanic eruptions be predicted? Why do people live in volcanic areas? 2 of 35 © Boardworks Ltd 2006

What is a volcano? A volcano is an opening or vent in the earth’s surface through which molten material erupts and solidifies as lava. Volcanic vent 3 of 35 © Boardworks Ltd 2006

Label this cross section of a volcano Volcanic bombs, ash, lava, gases Magma chamber Secondary cone Crater Main vent 4 of 35 © Boardworks Ltd 2006

Cross section of a volcano Crater Volcanic bombs, ash and gases Secondary cone Main vent Magma chamber 5 of 35 © Boardworks Ltd 2006

Cross section of a volcano 6 of 35 © Boardworks Ltd 2006

Volcanic emissions 7 of 35 © Boardworks Ltd 2006

Volcanic emissions 8 of 35 © Boardworks Ltd 2006

Do all volcanoes erupt? Active volcano – liable to erupt e. g. Mt Etna. Dormant (sleeping) volcano – a volcano which has not erupted for many years. For example, Mt Pinatubo erupted in 1991 after 500 years of dormancy. Extinct volcano – a volcano which has not erupted for many thousands or millions of years e. g. Edinburgh. However, it is often very difficult to tell whether a volcano will erupt again…El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years! 9 of 35 © Boardworks Ltd 2006

Learning objectives What is a volcano? Why do volcanoes occur? Where are volcanoes found? Can volcanic eruptions be predicted? Why do people live in volcanic areas? 10 of 35 © Boardworks Ltd 2006

Why do they happen? A destructive plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano. 11 of 35 © Boardworks Ltd 2006

Destructive plate boundary 12 of 35 © Boardworks Ltd 2006

Destructive plate boundary 13 of 35 © Boardworks Ltd 2006

Destructive plate boundary 14 of 35 © Boardworks Ltd 2006

Why do they happen? At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes. However, since the magma can escape easily at the surface, the volcano does not erupt with much force. 15 of 35 © Boardworks Ltd 2006

Constructive plate boundary 16 of 35 © Boardworks Ltd 2006

Constructive plate boundary 17 of 35 © Boardworks Ltd 2006

Constructive plate boundary 18 of 35 © Boardworks Ltd 2006

Types of Volcanoes are divided into three main types depending upon the material thrown out in an eruption 1. Composite Cone Volcano (ex. Mount St. Helens, Mount Etna) 2. Acid Lava Volcano (ex. Mount Pelee) 3. Shield Volcano (ex. Mauna Loa) 19 of 35 © Boardworks Ltd 2006

Volcano shapes Why do volcanoes have different shapes? 20 of 35 © Boardworks Ltd 2006

Volcano shapes 21 of 35 © Boardworks Ltd 2006

Volcano shapes 22 of 35 © Boardworks Ltd 2006

Volcanic activity at plate margins 23 of 35 © Boardworks Ltd 2006

Volcanic activity at plate margins 24 of 35 © Boardworks Ltd 2006

Learning objectives What is a volcano? Why do volcanoes occur? Where are volcanoes found? Can volcanic eruptions be predicted? Why do people live in volcanic areas? 25 of 35 © Boardworks Ltd 2006

Where are volcanoes found? Around which plate do we find most volcanoes? 26 of

Hawaii The Hawaiian islands are a chain of volcanoes in the Pacific Ocean. Look at their location on the map below. Why is this an unusual place for them to be located? 27 of 35 © Boardworks Ltd 2006

Hot spot volcanoes Why are the volcanoes to the left of the ‘hot spot’

Learning objectives What is a volcano? Why do volcanoes occur? Where are volcanoes found? Can volcanic eruptions be predicted? Why do people live in volcanic areas? 29 of 35 © Boardworks Ltd 2006

Predicting eruptions 30 of 35 © Boardworks Ltd 2006

Predicting eruptions 31 of 35 © Boardworks Ltd 2006

Predicting eruptions 32 of 35 © Boardworks Ltd 2006

Predicting eruptions 33 of 35 © Boardworks Ltd 2006

The problem of prediction Volcanologists (people who study volcanoes) are skilled at predicting the likelihood of an eruption. However, it's very difficult to pinpoint exactly when an eruption will happen. Often, moving magma doesn't result in an eruption, but instead cools below the surface. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred years, it's not possible to monitor every site. 34 of 35 © Boardworks Ltd 2006

Learning objectives What is a volcano? Why do volcanoes occur? Where are volcanoes found? Can volcanic eruptions be predicted? Why do people live in volcanic areas? 35 of 35 © Boardworks Ltd 2006

Why do people live in volcanic areas? This lava is weathered (broken down) to form a fertile soil. Can you think of any other reasons? Tourists are attracted to areas of volcanic activity. 36 of 35 Geothermal energy can be produced in many volcanic areas. © Boardworks Ltd 2006

Internet links Volcano World - a fun and informative web site http: //volcano. und. nodak. edu/ Virtual field visits http: //educeth. ethz. ch/stromboli/ The Michigan Technological University Volcanoes Page http: //www. geo. mtu. edu/volcanoes/ Global Volcanism Program http: //www. volcano. si. edu/gvp/ Fallout: Eye on the Volcano http: //www. nationalgeographic. com/features/98/volcanoes/ Savage earth http: //www. pbs. org/wnet/savageearth/ 37 of 35 © Boardworks Ltd 2006