Volcanoes

An arching orange lava fountain erupts from a vent on Kīlauea amid dark cooling lava. — Kīlauea, 25 February 1983. USGS photographed a lava fountain approximately 10 metres high; molten rock is at the surface, not throughout the mantle.

A suggested lesson sequence

Use these stages at your own pace. Pause for students to sketch, compare observations or lead part of the demonstration.

01
Observe
Compare the broad shield and steeper composite cone. Name viscosity as one influence on lava flow. Raise Gas drive independently. Basalt can fragment too; gas and external water matter.
Open Observe
02
Tinker
Switch to Fissure vents. A fissure is a crack, not a viscosity class. Open the cross-section and identify the conduit.
Open Tinker
03
Explain
Explain why viscosity alone cannot determine whether an eruption fragments magma or produces flowing lava.
Open Explain
04
Check
Choose an answer and explain your reasoning. Each question includes feedback.
Open Check

Rehearse with the model

The same scene and controls as the lab. Load it when you are ready; use Start projector for the full classroom view.

Before the lesson

Explain how magma viscosity influences volcanic form and eruption style, using shield and composite volcanoes as examples.

Open the model before the lesson and choose a view that makes the important feature easy to see. Drag to rotate, and use the on-screen controls to change one variable at a time. The Controls panel explains the available keyboard shortcuts.

Pause the animation at a useful moment. Ask students what should happen next, then play it to test their explanation.

Guide the demonstration

Compare the broad shield and steeper composite cone. Name viscosity as one influence on lava flow. Raise Gas drive independently. Basalt can fragment too; gas and external water matter.

Switch to Fissure vents. A fissure is a crack, not a viscosity class. Open the cross-section and identify the conduit.

Discuss a common misconception

“A volcano’s size alone predicts how explosive its next eruption will be.” Eruption behaviour depends on magma properties, gas, ascent conditions and possible interaction with water or ice. Large shield volcanoes often produce fluid lava flows, but basaltic eruptions can also be explosive. The existing landform records earlier activity without determining every future event.

Build the explanation

Magma composition, gas content and the conditions of ascent influence eruption style. Comparing volcanic forms helps connect those processes with lava flows, fragmental deposits and the structure built over time.

Switch to Fissure vents. A fissure is a crack, not a viscosity class. Open the cross-section and identify the conduit.

The displayed eruptions illustrate selected mechanisms; volcano shape alone cannot predict the next eruption.

Teaching notes

Compare effusive and explosive activity rather than assuming every volcano erupts in the same way.

Include hotspot and divergent-boundary examples as well as volcanoes around subduction zones.

Explain how repeated fluid lava flows build a shield volcano rather than describing it as an eroded stratovolcano.

Check understanding

Open Check for 4 questions. Ask students to explain their choice before revealing the answer.

Return to the opening photograph. Ask students to identify one visible feature and explain which part of the model helps account for it.

Look more closely

Use these observations to connect the vocabulary to features students can identify.

Shield volcano

The Hawaiian volcanic islands stretch across the Pacific beneath scattered white clouds in an ISS photograph. — Hawaii from the ISS. The volcanic chain records Pacific plate motion relative to a long-lived hotspot; the youngest main island is at the southeast end.

Read the definition

Stratovolcano

The broad conical slopes of Mount Fuji rise beyond Lake Kawaguchi in Japan. — Mount Fuji from Lake Kawaguchi, Japan. Repeated eruptions built a stratovolcano with layers of lava and fragmental deposits.