Home >> Science & Nature >> Nature

Stages of a Volcano Eruption

To the public, volcanoes may seem like fire-breathing dragons arriving in the night --- unseen, unpredictable and utterly devastating. The reality, however, is much more complex. There are many types of volcano and many types of eruption, and each behaves differently. While, some, like Mt. St. Helens, are destructive, others, like Kilauea in Hawaii, erupt regularly with harmless, slow, land-building lava flows. No matter the type, all go through similar stages and are predictable.

Invasion of Magma
- Rock melts inside the Earth's crust, forming magma. This magma is lighter than the solid rocks surrounding it, causing it to rise and collect in magma chambers underneath a volcano.
Building Pressure
- Pressure builds in the magma chambers as they fill, gaining energy for eruption. As magma rises inside a volcano, it causes a rise in seismic activity. Earthquakes of increasing severity occurred at Mt. St. Helens over two months before it exploded on May 18, 1980. The tremors opened a crater on the mountain's peak and formed a noticeable bulge on its northern side --- all signs of an imminent explosion.
Explosive Eruptions
- If the magma building in the volcano is thick and sticky, it will trap gases, resulting in an explosive eruption when the pressure becomes too intense. Magma explodes into the air in pieces called tephra that can range in size from ash particles to boulders. The debris falls from the air, forming a pyroclastic flow of gases and molten particles moving on the ground at high speeds. These, in addition to landslides, are the most dangerous part of an eruption.
Flowing Eruptions
- If the magma is thin and runs, gases can escape from it, resulting in a low-pressure, slow-moving flow of magma instead of a violent eruption. Non-explosive eruptions typically begin with a release of trapped gases called a "fire fountain," due to its appearance of sprayed fire. Magma will then flow from the volcano's top seeking the its lowest point --- almost always the sea. As magma flows are slow-moving, they are rarely dangerous to people but can damage property.

Nature