Why and How Volcanic Eruptions Occur

With a major volcanic eruption occurring in Hawaii last week, forcing a mass evacuation and destroying homes, it has many people wondering: “Why do volcanic eruptions occur?”

It’s cause for concern because there are hundreds of active volcanoes around the globe, and there is potential for destruction to all communities near these volcanoes.

The most destructive volcano in the history of the United States occurred on May 18, 1980, when Mount St. Helens in the state of Washington erupted.

In this article, we’ll talk about the Hawaii volcano and look at the underlying mechanics behind volcanic eruptions.

Hawaii’s latest volcanic eruption

The Kilauea Volcano erupted last Thursday on Hawaii’s Big Island with cracks emerging in the volcano’s East Rift Zone, an area of fissures miles away from the volcano’s summit, forcing the evacuation of 1700 people from Leilani Estates and nearby Lanipuna Gardens.

The eruption was followed by a 6.9-magnitude earthquake on Friday.

As of Sunday, 11 volcanic fissures had opened, venting lava and toxic fumes into the air.

How & why volcanoes erupt

The short answer is that volcanoes erupt because of density and pressure beneath the earth. Volcanic eruptions are earth’s natural method of releasing its internal pressure and heat.

Deep within the earth, conditions are so hot that some rocks melt slowly, becoming a thick flowing substance called magma.

The magma becomes lighter than the solid rock around it, rising and collecting in magma chambers.

Deep beneath volcanoes, there is gas in the magma, which is under high pressure and cannot escape.

Eventually, through vents, cracks and fissures in the earth surface, the pressure forces the magma to rise, pushing its way through, which we call “erupting.” The erupted magma is called “lava.”

To explode or not to explode

Volcanic eruptions can be explosive or non-explosive. If the magma beneath the earth is thin and runny, gases are able to easily escape. Therefore, when this type of magna erupts, it is able to flow out of the volcano without exploding, according to the US Geological Survey (USGS).

However, if the magma is thick and sticky, then gases are unable to easily escape. In this situation, pressure builds up until the gases escape violently through exploding.

Explosive eruptions are the most dangerous, as the blast of magma can be hurtled hundreds of feet into the air.

The lava breaks into pieces called “tephra” which can vary in size from tiny particles of ash to house-sized boulders.

It gets worse…

Volcanoes can blast out clouds of hot tephra, which then can race down mountainsides destroying everything in their path.

The next problem is the thick ash, which can come down in entire blankets and can suffocate plants, animals and humans.

Mud flows can also form when the hot volcanic materials mix with water, whether from streams, snow or ice. Entire communities located near volcanoes have been completely buried from resulting mud flows.