How does gas pressure affect the rise of magma in volcanic eruptions?

Deep in the Earth, almost all magmas contain gas dissolved in the liquid, but the gas forms a separate vapor phase when the pressure drops as the magma rises towards the Earth's surface. Gas gives magma its explosive character because the volume of gas expands when the pressure is reduced.

How do dissolved gases cause explosive eruptions?

The standard explanation for explosive volcanism is that as liquid magma rises from a magma chamber at a depth of several miles, dissolved gases—mostly water—form bubbles. As bubbles grow, the total magma volume increases, causing it to rise even faster.

Why is it dangerous to live near an active volcano?

In addition, the thermal energy from some volcanoes can be used to generate electricity. But if you live too close to a volcano – and it erupts – it can be deadly. If you live with a volcano like Merapi, it's wise to watch it closely. Volcanoes provide fertile soil – as well as deadly hot hurricanes of lava and ash.

How does the gas content of a volcano affect the eruption?

This also applies to volcanoes. When the bubbles escape, they push out the magma, causing a spewing eruption. This content is not compatible on this device. The nature of this eruption depends mainly on the gas content and viscosity of the magma material.

How is the severity of a magma eruption determined?

The severity of the eruption depends mostly on the composition of the magma. The first question to address is: why does the magma erupt at all? That breakout force generally comes from the internal gas pressure. The material that forms magma contains a lot of dissolved gases – gases that have been suspended in the magma solution.

How is the nature of an eruption related to viscosity?

When the bubbles escape, they push out the magma, causing a spewing eruption. The nature of this eruption depends mainly on the gas content and viscosity of the magma material. Viscosity is simply the ability to resist flow – basically, it's the opposite of fluidity.

Why does the vapor pressure of magma increase?

The vapor pressure increases because the magma cools, which initiates a crystallization process that enriches the gas content of the magma. In either case, what you get is magma filled with tiny gas bubbles, which have a much lower density than the surrounding magma, and then push out to escape.