Volcanoes

Question 1

Where are volcanoes found?

Answer 1

• destructive plate margins

- constructive plate margins

Question 2

How are volcanoes formed at destructive plate margins?

Answer 2

• oceanic plate goes under the continental plate because it’s denser
• oceanic plate moves down into the mantle where it’s melted and destroyed
• pool of magma forms
• magma rises through cracks in the surface (vents)
• magma erupts onto the surface (now called lava) and forms a composite volcano

Question 3

How are volcanoes formed at constructive plate margins?

Answer 3

• magma rises up into the gap created by the plates moving apart
• this forms a shield volcano

Question 4

What is a hotspot?

Answer 4

• parts of the mantle that are very hot

- sometimes volcanoes can form on these (e.g. in Hawaii)

Question 5

What is a composite volcano?

Answer 5

• e.g. Mount Fuji in Japan
• made up of ash and lava that has erupted, cooled and hardened into layers
• lava is usually thick and flows slowly
• lava hardens quickly to form a steep-sided volcano

Question 6

What is a shield volcano?

Answer 6

• e.g. Mount Loa on the Hawaiian Island
• Made up of layers of only lava
• runny lava that flows quickly and spreads over a wide area which forms a low, flat volcano

Question 7

What is a dome volcano?

Answer 7

• e.g. Lassen Peak in California
• made up of layers of only lava
• thick lava that flows slowly and hardens quickly which forms a steep-sided volcano
• similar to the composite volcano, but only made up of hardened lava, not ash

Question 8

Why is it important to predict volcanic eruptions?

Answer 8

• millions of people live in places where volcanic eruptions can happen
• so many lives are at risk
• damage caused can be minimised

Question 9

How do scientists predict volcanic eruptions?

Answer 9

• seismometers to detect small earthquakes that can cause an eruption
• thermal imaging techniques/satellite cameras to detect temperatures around a volcano
• chemical sensors/Spiders are used to detect sulphur levels in the atmosphere around the volcano
• tiltmeters monitor changes in landscape on the volcano
• looking at the past history of the eruptions so volcanologists can identify any patterns in activity

Question 10

How do can volcanologists tell is a volcanic eruption is likely?

Answer 10

• hundreds of small earthquakes occur as magma rises through the Earth’s crust
• temperature around the volcano rises as activity increases and magma begins to rise through the main vent
• higher sulphur content as the volcano becomes closer to erupting
• changes in the volcano’s shape such as bulges in the land where magma has built up under it

Question 11

Why do people live near volcanoes?

Answer 11

• volcanic rock and ash provide fertile rock which results in a higher crop yield for farmers
• tourists are attracted to the volcano which increases economy
• geothermal energy can be harnessed which provides cheaper energy
• some precious minerals are contained in lava (like diamonds) which can be mined to make money