Volcanoes
Volcanoes erupt when magma reaches the surface.
About this topic
Volcanoes form where magma reaches the surface, usually at plate boundaries or hotspots like Hawaii. Magma rich in silica is thick and sticky, producing explosive eruptions (stratovolcanoes like Mount St. Helens), while runny basalt magma makes gentle shield volcanoes. Products include lava, ash, pyroclastic flows and gases.
Eruptions create new land and fertile soil, but also hazards, and ash can affect climate. Volcanologists monitor gas emissions, ground swelling and seismic activity to give warnings. Volcanoes are classified as active, dormant or extinct.
Two famous eruptions make the contrast clear. In 1980, Mount St. Helens blew out the side of the mountain, sending ash 24 km into the sky, because thick, gas-rich magma trapped pressure. In Hawaii, Kilauea produces fluid lava flows that can travel slowly enough for people to move out of the way, though they destroy buildings. The 1815 eruption of Tambora caused the 1816 year without a summer, with crop failures in Europe and North America, showing that big eruptions can cool the climate by sending sulfur aerosols into the stratosphere.
Volcanic rock weathers into some of the richest soils, which is why people farm on volcano slopes such as in Indonesia and Italy. Geothermal energy from volcanic regions heats homes in Iceland. Pyroclastic flows, fast clouds of hot gas and ash, are the deadliest hazard, as in Pompeii in 79 CE. A common misconception is that all volcanoes are cone-shaped mountains that erupt lava; some are huge calderas such as Yellowstone, and extinct is not the same as dormant, as dormant ones may erupt again.
Key ideas
- Found at plate boundaries and hotspots
- Lava vs ash eruptions
- Shield and composite types
Quick check
Use cases: where Volcanoes helps
- Homework: review the key idea behind Volcanoes before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Volcanoes without notes.
- Visual learning: play with the interactive lab to see how Volcanoes changes when you adjust its inputs.
- Teaching a friend: explain Volcanoes in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is Volcanoes?
Volcanoes erupt when magma reaches the surface.
What will I learn in Volcanoes?
Found at plate boundaries and hotspots. Lava vs ash eruptions. Shield and composite types.
Is Volcanoes part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Volcanoes lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Volcanoes?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.