Year 5 · Science · 2 minutes
What makes a volcano erupt?
Melting rock, rising magma, building pressure.
Key terms
- magma
- Hot, runny rock that forms when rock deep down melts.
- magma chamber
- The space under a volcano where rising magma collects.
- pressure
- The force that builds up as more magma squeezes in, until the rock above cannot hold it.
- lava
- Magma that pours out of a volcano, flowing in glowing rivers when it is runny.
- eruption
- When gas rushes out and the volcano blasts out lava or clouds of ash.
- GeoNet
- The scientists who watch our volcanoes day and night so people get a warning.
Transcript
Aotearoa is home to some amazing volcanoes, from snowy Ruapehu to the islands of Auckland. But what actually makes a volcano erupt?
Deep under the North Island, one giant plate of the Earth is slowly sliding underneath another. As it sinks, rock deep down melts into hot, runny rock called magma.
Magma is lighter than the solid rock around it, so it slowly rises, and collects in a magma chamber under the volcano. It's full of gas, a bit like a fizzy drink.
As more magma squeezes in, the pressure builds and builds. When the rock above can't hold it any more, the gas rushes out, and the volcano erupts!
Runny magma lets the gas escape gently, so lava pours out in glowing rivers. Thick, sticky magma traps the gas, so it blasts out in huge clouds of ash.
Auckland is built on a field of about fifty small volcanoes. Rangitoto, the youngest, appeared only about six hundred years ago. And Lake Taupō fills a giant crater, left by huge eruptions long ago.
Scientists at GeoNet keep watch on our volcanoes, day and night, so people get a warning if one starts to wake up.
So, melting rock makes magma. Magma rises and fills up with gas. And when the pressure is too much, the volcano erupts.
Sources
Every fact in the video, and where it comes from.
- 1gns.cri.nz/Home/Learning/Science-Topics/Volcanoes
- Pacific Plate subducts beneath the North Island
- 2geonet.org.nz/about/volcano/aucklandvolcanicfield
- Auckland volcanic field has about 50 volcanoes (GeoNet: 53 centres)
- Rangitoto is the youngest, about 600 years old
- 3gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/New-Zea…
- Lake Taupō occupies a caldera formed by large eruptions
Image and sound credits
- “Le Ngauruhoe et le Ruapehu vus du sommet du Tongariro” by Eusebius, CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)
- “Mount Ruapehu (51620400176)” by Geoff McKay from Palmerston North, New Zealand, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)
- “Mt. Eden's crater - 16305880672” by Francisco Anzola, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)
- “HVO scientist takes video of Kīlauea summit eruption (96754)” by USGS Hawaiian Volcano Observatory (Public domain)
- “USGS Hawaiian Volcano Observatory scientist monitors Kīlauea Volcano's Lower East Rift Zone lava flow on 6-25-2018 (45542229424)” by Hawai‘i Volcanoes NPS (Public domain)
- “ISS-66 Atmospheric plume from 2022 Hunga Tonga eruption - edited” by NASA / Kayla Barron (Public domain)
- “Rangitoto Island, Auckland 1010, New Zealand - panoramio (8)” by Andrew Harvey, CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)
- “Lake Taupo, New Zealand, 1990 - Flickr - PhillipC” by Phillip Capper from Wellington, New Zealand, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)
- “HVO scientists monitor ongoing eruption (96755)” by USGS Hawaiian Volcano Observatory (Public domain)
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