Teacher sheet · Ages 10–11 · about 45–50 minutes
Runny lava and explosive ash
Lesson page: echoesof.science/school/volcanoes/ages-10-11/ · Pupil worksheet: echoesof.science/school/volcanoes/ages-10-11/print/
Learning aims
- Explain why magma rises and the difference between magma and lava.
- Link runny or sticky magma to flowing or explosive eruptions.
- Name shield, composite and cinder-cone volcanoes.
- Know that most volcanoes are found at plate edges or hot spots.
- Plan and carry out a fair test.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: show photos of Hawaii's lava flows and an ash column. Why so different? |
| 10 min | Read the text; find the Ring of Fire, Hawaii, Etna and Iceland on a world map. |
| 20 min | Lava race (fair test). |
| 5 min | Play Flowing or exploding? |
| 5 min | Quiz and discussion. |
Materials for the experiment
- A tray or board, propped up at one end on 2 books
- A ruler and masking tape
- 4 liquids: water, cooking oil, golden syrup or honey, ketchup
- 4 teaspoons
- A stopwatch
- Paper towels
Safety: Wipe up spills at once so nobody slips. Do not taste the liquids. Wash hands afterwards. Keep the slope low so the tray cannot slide off the table.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Magma comes from the Earth's molten core. | Magma forms where rock melts deep underground, and it rises because it is lighter than the solid rock around it. |
| All volcanoes are cone-shaped mountains that explode. | Shield volcanoes are wide and gentle and mostly pour out runny lava. |
| Volcanoes can be anywhere. | Most are at plate boundaries, such as the Ring of Fire, or over hot spots like Hawaii. |
Worksheet answers
- Shield: wide, low, gentle slopes made of lava flows. Composite: tall, steep cone made of layers of lava, ash and rocks.
- Usually the golden syrup/honey or ketchup; fair: same amount, same slope, same start and finish line, same timing method, repeated.
- Gas cannot escape from thick, sticky magma, so pressure builds up until the gas bursts out violently.
- Cooler (red is about 600–800 °C, yellow about 1,000–1,200 °C).
Quiz answers
- Why does magma rise? It is lighter than the solid rock around it. Magma is less dense than the rock around it, so it rises.[1]
- What happens when gas cannot escape from thick, sticky magma? Pressure builds until it explodes. Trapped gas builds pressure until it bursts out violently.[1]
- Which volcano is wide with gentle slopes, built from runny lava? A shield volcano. Shield volcanoes are built almost entirely of fluid lava flows.[2]
- Lava glows orange. About how hot is it? 800–1,000 °C. Orange lava is about 800–1,000 °C.[7]
- Where are many volcanoes found? Where plates of the Earth's crust meet. Many lie at plate edges, such as the Ring of Fire.[4]
- About how many eruptions happen on Earth each year? About 50 to 70. Volcanoes erupt roughly 50 to 70 times a year.[8]
Going further
Plot the race times on a bar chart. Then research one volcano (for example Etna, Stromboli or Kīlauea) and decide whether its eruptions are mostly flowing or explosive.
Sources used in this lesson
- [1] How do volcanoes erupt? (US Geological Survey (USGS)): reliability High
- [2] About Volcanoes (USGS Volcano Hazards Program): reliability High
- [3] What is the Ring of Fire? (US Geological Survey (USGS)): reliability High
- [4] This Dynamic Earth: the Ring of Fire (US Geological Survey (USGS)): reliability High
- [6] This Dynamic Earth: Hotspots (US Geological Survey (USGS)): reliability High
- [7] How hot is a Hawaiian volcano? (US Geological Survey (USGS)): reliability High
- [8] Volcanoes (British Geological Survey (BGS)): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/volcanoes/sources/
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