Volcanoes
This Topic is About...
- I will identify features of volcanoes from pictures and diagrams.
- I will draw a diagram to represent a volcano.
- I will describe where volcanoes erupt at breaks in the Earth’s crust.
You’re going to be a science explorer!
Key Words
- ash
- composite volcano
- crater
- erupt
- lava
- plateau
- risk
- secondary cone
- vent
Tap to Learn the Meanings!
- ash: Tiny bits of rock and dust thrown into the air during a volcanic eruption.
- composite volcano: A tall volcano made of layers of lava and ash.
- crater: A bowl-shaped hole at the top of a volcano.
- erupt: When a volcano explodes and sends out lava, ash, and gases.
- lava: Hot, melted rock that flows out of a volcano.
- plateau: A large, flat area of land raised above the surrounding ground.
- risk: The chance that something dangerous or harmful might happen.
- secondary cone: A smaller cone that forms on the side of a volcano from new eruptions.
- vent: An opening in the Earth’s surface where magma and gases come out.
Amazing! You’re mastering volcano vocabulary!
How do volcanoes happen?
Sometimes a big crack develops in the Earth’s crust. Magma from the mantle travels up the crack and shoots out or erupts on the surface of the Earth. This is called a volcano. Once the magma erupts on to the surface, the magma is called lava.
Different types of volcano
Lava can be very hot, sometimes 1000°C. When it is very hot, the lava flows quickly over the surface of the Earth. Eventually the lava will stop flowing, and then it cools and hardens into rocks. The islands of Hawaii in the Pacific Ocean are made of layers of lava. The lava has flowed, cooled and hardened into rocks. The layers of lava form a flat surface called a volcanic plateau.
Besides lava, some volcanoes send out rocks, volcanic ash and gases. All these materials flow up a central pipe, or vent. During the eruptions, the vent widens at the surface to form a crater.
The most common type of volcano is a composite volcano. It has layers of ash and lava. The ash is burnt lava. The ash and lava build up a cone-shaped mountain with smooth sides. Some of the magma forces its way through cracks in the sides of the volcano. When this magma erupts it forms baby volcanoes called secondary cones.
FUN QUESTIONS
Look at the photograph of flowing lava.
1. Point to the lava that is still flowing.
Show answer
2. Point to the lava that has cooled down and hardened into rocks.
Show answer
Look at the diagram of a volcano and the photograph of a volcano. The diagram is a model of the real thing.
3. Talk about features of the volcano that you can see on the photograph and the diagram.
Show answer
Let’s Investigate!
Question: How can we show the internal structure of a volcano using a labelled diagram?
Activity:
- Look at a photograph of a volcano.
- Draw a diagram to show the internal structure of the volcano shown in the photograph.
- Label the main parts of the volcano clearly.
Checklist: How am I doing?
- Did I show the photograph of a volcano as a diagram?
- Did I add features to show the internal structure of the volcano?
- Did I label the features correctly?
Tap to See Example Answer
- Example diagram labels: crater, main vent, secondary vent, magma chamber, lava flow, ash cloud, side vent, cone shape.
- Explanation: The magma chamber holds molten rock (magma) beneath the surface. When pressure builds up, magma travels through the vent and erupts from the crater as lava, forming a cone-shaped volcano.
- Tip: Use arrows and neat handwriting for labels, and make sure all internal parts are drawn inside the volcano outline.
Well done! You’ve shown how to represent real-world features with a clear scientific diagram.
Which parts of the world have volcanoes?
Some areas of the world have a high risk of a volcanic eruption. This is because there are many cracks in the Earth’s crust in these areas. Magma can move up these cracks and erupt at the surface.
Other areas of the world have no cracks in the crust. These areas have a low risk of a volcanic eruption.
How do volcanoes affect people?
You probably think that volcanoes only cause death and destruction! But millions of people live in volcanic regions. They know the risks. Volcanoes have positive as well as negative effects. Look at the drawing.
- People can be injured or killed by ash and hard lumps of lava.
- Lava burns and buries crops and buildings.
- Ash covers buildings and crops. People become ill when they breathe in ash and poisonous gases.
- Underground water is heated by magma. This water comes to the surface as hot springs. These are tourist attractions.
- Tourists come to watch volcanoes erupting, providing employment for many people in volcanic regions.
- Underground water in volcanic regions is hot enough to heat people’s houses and make electricity.
- Lava makes good soil. Ash fertilises the soil, helping crops grow very well.
FUN QUESTION
Discuss which of the seven results of a volcanic eruption are positive effects and which are negative effects.
Show answer
Negative effects: Lava flows destroy buildings and vegetation, ash clouds can harm health, and eruptions can cause loss of life and disrupt transport.