Volcanoes Flashcards
1
Q
Where are volcanoes found?
A
- destructive plate margins
- constructive plate margins
2
Q
How are volcanoes formed at destructive plate margins?
A
- 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
3
Q
How are volcanoes formed at constructive plate margins?
A
- magma rises up into the gap created by the plates moving apart
- this forms a shield volcano
4
Q
What is a hotspot?
A
- parts of the mantle that are very hot
- sometimes volcanoes can form on these (e.g. in Hawaii)
5
Q
What is a composite volcano?
A
- 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
6
Q
What is a shield volcano?
A
- 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
7
Q
What is a dome volcano?
A
- 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
8
Q
Why is it important to predict volcanic eruptions?
A
- millions of people live in places where volcanic eruptions can happen
- so many lives are at risk
- damage caused can be minimised
9
Q
How do scientists predict volcanic eruptions?
A
- 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
10
Q
How do can volcanologists tell is a volcanic eruption is likely?
A
- 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
11
Q
Why do people live near volcanoes?
A
- 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
