Volcanoes & Their Products
Geography: KS3, topic 11.2.1
Volcanic Eruptions
When a volcano erupts at the Earth's surface, it can produce lots of different things, including:
Lava
- Lava is magma (molten rock) above the surface of the Earth.
Gases
- Volcanoes emit lots of gases like sulfur.
Ash
- Ash is tiny pieces of burnt rock fragments that are blown into the atmosphere, usually at some force.
- These pieces fall on land and can float in the air, causing a volcanic winter (by blocking out the sun).
- A volcanic winter describes when a volcano erupts, producing lots of ash, which then blocks the sun.
- Mount Pinatubo's 1991 eruption reduced global temperatures for 3 years.
Pyroclastic flows
- Pyroclastic flows are currents of hot ash, lava and gas that can move downhill at speeds of up to 500km/h during an eruption.
- Pyroclastic flows are impossible to outrun.
- Pyroclastic flows can reach temperatures of up to 1000oC and can cover distances of up to 30km from the volcano.
Types of Volcano
The 2 main types of volcano are shield volcanoes and composite volcanoes.
Shield volcanoes
- Found at divergent tectonic plate margins or hotspots (like in the Pacific).
- Not particularly explosive.
- They release 'basaltic lava' when the volcano erupts. Basaltic lava is like a liquid that flows gradually, creating a volcano with a gentle gradient (rather than a steep slope).
- Shield volcanoes do not produce any ash.
Composite volcanoes
- Found at convergent tectonic plate boundaries.
- Erupt explosively.
- Instead of basaltic lava, composite volcanoes erupt andesitic lava.
- Andesitic lava is thicker than basaltic lava because it has more silica in it.
- Because andesitic lava is thicker, it travels less far and composite volcanoes have steeper sides, forming a cone shape.
- Mount Pinatubo, Mount Vesuvius in Italy and Mount Fuji in Japan are examples.
How do shield and composite volcanoes differ?
Test yourself on Volcanoes & Their Products
Which of the following is NOT a product of volcanic eruptions?
Which type of volcano erupts explosively & produces andesitic lava?
Which type of volcano produces basaltic lava and does NOT erupt explosively?
Which of the following is NOT a type of volcano?
Toggle until all answers are correct: Which of the following is true of shield volcanoes?