Why do volcanoes erupt?
Deep within the Earth, temperatures are so high that some rocks are beginning to melt. However, as rocks melt, their mass remains the same but their volume increases. As a result, they are converted to magma that is less dense than the surrounding and overlying rocks.
Now, due to buoyancy, this lighter magma begins to rise toward the Earth's surface and is collected in magma chambers.
Eventually, this magma passes through vents and fissures and erupts onto the Earth's surface.

The references:
https://www.usgs.gov/faqs/how-do-volcanoes-erupt
https://www.scientificamerican.com/article/what-causes-a-volcano-to-erupt-and-how-do-scientists-predict-eruptions/

Timecodes
0:00 – Why do volcanoes erupt?
0:54 – What causes earthquakes?
1:55 – Why do we see lightning before thunder?
3:07 – What is a tsunami?
4:16 – Where is the largest waste dump on Earth?
6:09 – Why do we weigh less in water?
7:45 – Why is soap ineffective in hard water?
9:10 – Why do copper containers turn green?

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