what makes a volcano erupt

A volcano erupts when magma from beneath the Earth's crust rises to the surface due to being less dense than the surrounding solid rock. As magma ascends, pressure decreases, allowing gas bubbles to form within it. The increasing pressure from these gas bubbles pushes magma through cracks in the Earth's crust. When the pressure overcomes the strength of the crust, it causes an eruption. The magma then escapes as lava, ash, and gases. This process is often driven by tectonic plate movements, where plates either diverge, converge, or one subducts under another, creating the conditions for magma formation and pressure buildup. The type of eruption depends on the magma's viscosity and gas content, influencing whether it is explosive or more gentle lava flow.