Beyond the Surface of a Volcano

Written by: Paige Leal

Have you ever heard of Pompeii, the city that was frozen in time due to one of the most famous volcanic eruptions? There are many reasons for why a volcano can erupt but this piece in history shows just how powerful volcanoes can be.

What causes Volcanoes to Erupt 

Volcanoes erupt because of what’s happening deep inside Earth. Heat from the planet’s interior causes rock in the mantle and lower crust to partially melt and form magma, which is less dense than solid rock. This slowly rises toward the surface. When magma gathers in magma chambers, the pressure builds, and once that pressure becomes greater than the weight of the rock sitting above, the magma forces its way out through cracks and vents. Next thing you know, lava is spilling out of the rock, and there you have an eruption. 

Types of Eruptions

Not all volcanic eruptions are the same, with some being slow and steady, while others are violently explosive. When magma is runny and fluid (low viscosity), gas can escape easily, producing lava flows, rather than big explosions. When the magma is thick and sticky, gases can’t escape as easily. This traps pressure, and when it finally breaks free, the eruption can be explosive, blasting ash and volcanic rock high into the sky. 

Gases

Gases, such as water vapor, carbon dioxide, and sulfur compounds dissolved in magma, play a major role in eruptions. As magma rises and pressure drops, these gases form bubbles that expand rapidly and force magma upward. The more gas in the magma, especially in thicker magma, the more likely the eruption is to be violent.

Eruptions Effects

Volcanoes are powerful, they can destroy landscapes and lives with ash plumes, pyroclastic flows (hot fragments and gas racing downhill), and fast moving mudflows called lahars. They can even lead to entire cities being wiped away, such as Pompeii. But volcanoes don’t just wreck things, they also build land. Lava can form new rock, and repeated eruptions can create volcanic mountains, islands, and fertile soil.

Volcanoes erupt when molten rock and trapped gases deep within the Earth build up pressure over time. The way a volcano erupts, whether it slowly oozes lava or violently explodes, depends on the magma’s thickness and the amount of gas it contains. History shows the incredible power of these eruptions, such as when Mount Vesuvius buried the city of Pompeii under ash and lava, freezing the city in time. Scientists can monitor warning signs like earthquakes, ground swelling, and gas emissions to anticipate eruptions, but the forces of nature are always unpredictable, capable of both destruction and creating new land.