How Volcanoes Erupt

Overview

Students investigate how magma, gases and pressure cause a volcanic eruption. Using an information sheet, they complete a labelled volcano diagram and explain the sequence from magma rising underground to lava, ash and gases being released at the surface. The lesson builds knowledge needed for later learning about eruption prediction and hazard management.

Learning intentions

• WALT explain how a volcano erupts.
• WALT identify the main parts of a volcano.
• WALT use information from a scientific text to complete a diagram.
• WALT describe how pressure and gases contribute to an eruption.

Success criteria

• I can correctly label the magma chamber, conduit, vent, crater, lava flow, ash cloud and layers of rock.
• I can explain that magma rises because of heat, buoyancy and pressure from dissolved gases.
• I can describe the sequence of an eruption using scientific vocabulary.
• I can use evidence from an information sheet rather than guessing.

Curriculum links

• Geography — Earthquakes and volcanic eruptions: how volcanoes erupt.
• Geography — Earthquakes and volcanic eruptions: prediction through monitoring tremors, land distortion and temperature changes.
• Geography — Earthquakes and volcanic eruptions: conducting a case study.
• Science capabilities: interpreting representations, gathering and interpreting information, and communicating explanations.

Lesson structure (60 minutes)

1. 0–5 min · Hook and prior knowledge. Teacher opens with the volcanic eruption hook slide, showing a striking photograph or image of an erupting volcano, and asks, “What has to happen underground before we see this?” Students make an individual prediction, then share one idea with a partner. Invite several responses without correcting them yet.

2. 5–15 min · Build the model. Teacher uses the volcano structure and eruption sequence slides to introduce magma, magma chamber, conduit, vent, crater, lava, ash and gases. Explain that magma is molten rock beneath Earth’s surface and becomes lava when it reaches the surface; dissolved gases expand as magma rises, increasing pressure. Students create a quick sequence in their books: magma collects → gases expand and pressure increases → magma rises → material erupts.

3. 15–20 min · Demonstrate reading the diagram. Teacher displays the worked labelling example and models finding a key word in the information sheet, locating the matching feature on the diagram, and checking whether the label makes sense. Emphasise that arrows and labels must identify the correct part, not simply be placed near the volcano. Students help complete two example labels and explain the evidence used.

4. 20–40 min · Paired information-to-diagram task. Teacher distributes the volcano eruption information-and-labelling worksheet to pairs, briefly reads the instructions aloud, and circulates to question thinking: “Which sentence helped you?” Students read the information sheet, fill in the missing labels on the volcano image, and complete the eruption sequence. Each student records their own answers, while pairs discuss unfamiliar words and justify choices using the text. At the halfway point, pause for a 60-second check: students compare one label with a nearby pair and correct it only if they can identify evidence.

5. 40–52 min · Construct an explanation. Teacher returns to the explanation prompt and model answer slide and asks students to use at least four scientific terms in a short response: “Explain how pressure can lead to an eruption.” Students independently write a five-to-seven-sentence explanation, using the labelled diagram and information sheet. Encourage a clear chain of cause and effect: heating and melting, magma movement, gas expansion, pressure, opening or fracture, and eruption.

6. 52–60 min · Share, assess and exit. Teacher displays the review and exit-question slides and conducts a quick whole-class check using hands-up responses or mini whiteboards. Students answer: “Why do gases make an eruption more likely as magma rises?” They then complete the final question on the worksheet: “Describe one way scientists monitor a volcano before an eruption.” Collect worksheets to assess both diagram accuracy and explanations.

Resources

• the volcanic eruption teaching deck
• the volcano eruption information-and-labelling worksheet
• Projector or interactive display
• Student books or lined paper
• Pens, pencils and coloured pencils
• Mini whiteboards or scrap paper for quick checks
• One worksheet per student, used for paired reading and individual recording

Assessment

• During questioning, listen for the distinction between magma underground and lava at the surface, and address the misconception that volcanoes “explode because they are hot” without pressure or gases.
• Check paired worksheets for accurate labels and evidence-based use of the information sheet. Confer with students who confuse the conduit, vent and crater.
• Use the written explanation and exit question to assess whether students can link gas expansion and pressure to an eruption and recognise that monitoring can provide warning information.

Differentiation

• Provide a word bank on the board with a simple definition and visual cue for each key term. Students needing support may highlight matching words in the information sheet before labelling.
• Offer sentence starters: “Magma begins to rise when…”, “As the magma rises, gases…”, “The pressure causes…”, and “Scientists can monitor…”.
• Pair students deliberately so that reading support is available, while requiring each student to complete and explain their own diagram.
• Extend confident students by asking them to explain why a volcano may produce lava flows, ash or explosive eruptions, and to connect increasing tremors or land distortion with rising magma.