When a volcano erupts, pressure builds up beneath the Earth's surface, causing magma to rise and eventually breach the surface, leading to a volcanic eruption. As the magma reaches the surface, it is exposed to lower pressure, which allows gases dissolved in the magma to expand and escape. This process can result in explosive eruptions, where lava is ejected forcefully into the air, or effusive eruptions, where lava flows more steadily from the volcano's vent.

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