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Volcanoes Plate Tectonics. Contents. What is a volcano? Why do volcanoes occur? Where are volcanoes found? A case study: Mount St Helens Can eruptions be predicted? Why do people live in volcanic areas? Summary activities. The key concepts covered are:
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Contents • What is a volcano? • Why do volcanoes occur? • Where are volcanoes found? • A case study: Mount St Helens • Can eruptions be predicted? • Why do people live in volcanic areas? • Summary activities The key concepts covered are: Place, Space and Physical and human processes.
What is a volcano? What is a volcano? By the end of this section, you will: • Know what a volcano is and what happens beneath the surface of a volcano. • Understand about the different types of volcano that exist.
What is a volcano? A volcano is an opening, or vent, in the earth’s surface. Volcanic vent This opening allows molten lava to erupt through it and solidify as igneous rock. Other materials are also ejected. What happens beneath the surface to cause an eruption?
Volcano types There are three different types of volcano. Geographers call the categories active, dormant or extinct. • An active volcano is liable to erupt at any time, e.g. Mt Etna. • A dormant volcano has not erupted for years. Mt Pinatubo erupted in 1991 after 500 years of dormancy. • An extinct volcano has not erupted for a very long time and is unlikely to erupt again, e.g.Edinburgh. Categorizing volcanoes can be tough. Chaitén in Chile erupted in 2008 for the first time since 7400BC!
Why do volcanoes occur? Why do volcanoes occur? By the end of this section, you will: • Know more about how plate tectonics cause the formation of volcanoes. • Understand the role destructive and constructive boundaries play in the formation of volcanoes.
Plate movements The surface of the Earth is covered in plates that are in constant motion. • The motion of the plates can cause problems to the surface of the Earth. • Most of these problems occur at plate boundaries. • A plate boundary is where the edges of two plates meet. The vast majority of the Earth’s volcanoes can be found on a plate boundary.
Where are volcanoes found? Where are volcanoes found? By the end of this section, you will: • Be able to recognize the areas of the Earth where volcanoes are usually found. • Know what is meant by the term ‘Ring of Fire’. • Know what is meant by a hot spot volcano.
Where are volcanoes found? Volcanoes are usually found at plate boundaries. One area of the world is well-known for the number of volcanoes around it. This area is known as the ‘Ring of Fire’. The Ring of Fire is located around the Pacific rim. Can you think of any volcanoes that are located on the Ring of Fire?
Hawaii The Hawaiian islands are a chain of volcanic islands that are situated in the Pacific Ocean. Why is this an unusual place for them to be located? Most volcanoes are located on plate boundaries. Hawaii is nowhere near a plate boundary. Why are the Hawaiian islands volcanic?
A case study – Mount St Helens A case study: Mount St Helens By the end of this section, you will: • Have a better understanding of what happened in the Mount St Helens eruption. • Understand what some of the consequences of the eruption were. • Realize what damage the eruption caused.
Mt St Helens – consequences of the eruption The effects of the Mount St Helens eruption were enormous. • The pyroclastic surge spread 27km from the volcano and flattened acres of woodland. • Ash clouds stretched 26km above sea level. However, there were some positives. • Some plants and animals were resilient enough to survive. • The lack of human interference encouraged nature to spring forth again.
Back to the future What does the future hold for Mount St Helens? Since 1980, there has been more activity on Mount St Helens. • Between 1980 and 1986 a new lava dome was formed. • Magma reached the surface of the mountain in October 2004. • In 2005, a 36,000 foot plume of steam was emitted. There was also a small earthquake. It seems likely that Mount St Helens will erupt again in the future. Will we be able to tell when?
Can eruptions be predicted? Can eruptions be predicted? By the end of this section, you will: • Know what a volcanologist does. • Understand some of the difficulties that are associated with predicting volcanic eruptions.
The problem of prediction Volcanologists – people who study volcanoes – are skilled at predicting the likelihood of an eruption. However, it is difficult to pinpoint when an eruption will happen. • The movement of magma may be detected, but often no eruption occurs. Instead it 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.
Why do people live in volcanic areas? Why do people live in volcanic areas? By the end of this section, you will: • Know why people are attracted to live near volcanic areas. • Realize some of the pros and cons of living alongside a volcano.
Why do people live in volcanic areas? Although volcanic areas are exceptionally dangerous, there are still a lot of people who live in zones that are affected by volcanic eruptions. Why? • Tourists are attracted to areas of volcanic activity. This provides money for the local economy. • The lava produced by the volcano is weathered (broken down) to form a fertile soil. This is perfect for growing crops. • Geothermal energy can be produced in many volcanic areas. Can you think of any other reasons?
Summary activities Summary activities By the end of this section, you will: • Know the key points of volcanoes and volcanic eruptions. • Understand important words and phrases relating to volcanoes.
