Volcanic Hazards to Watch Out For

When we think of volcanic hazards, a hot stream of flowing lava is the first thing that comes to mind. However, there are several other dangers that come along with a volcanic eruption, many of which are more harmful than the initial flow of lava. The most common (and deadly) of these volcanic hazards are the subsequent earthquakes and landslides caused by the Earth shifting during the volcano's eruption. The most well-known volcanic landslide occurred in 1980, when the northern side of Mount St. Helens slid off, killing 57 people.

Volcanic hazards: Seismic activity and earthquakes

The violent act of a volcanic eruption can lead to a series of lava-related earthquakes in the area. When a volcano erupts, the hot magma rises up through the Earth's crust, shifting the rock above it. This causes breakages in the surrounding rock and shifts in the plates of the Earth. Scientists who study volcanoes (called volcanologists) will generally set up several seismic monitoring devices during or after a volcanic eruption. The seismic equipment tells the volcanologist how deep below the volcano the earthquake's epicenter is. This lets them know if the hot magma is still on the rise deep inside the volcano or if it has already reached its peak.

Volcanic hazards: Landslides

The movement and shifting that occurs during an eruption can also lead to the volcanic hazard of landslides. Most volcanoes have a steep slope that becomes unstable both inside and out during a violent eruption. Volcanic earthquakes can further crumble the slope of the volcano, which is often made up of old layers of ash and lava from previous eruptions. This loose ash is not very stable, so when it is shaken by a new eruption, it tends to slide right off of the volcano's slope.

Volcanic hazards: The Mount St. Helens landslide

In 1980, the Mount St. Helens eruption caused a massive volcanic landslide that destroyed the entire northern slope of the mountain. Geologists had noticed the warning signs of the oncoming volcanic landslide, but were powerless to stop it from happening. The rising magma inside the volcano had created a large bulge on the northern side of the volcano's slope. This bulge weakened the bottom part of the slope and it was only a matter of time before the entire side came falling down onto the homes below. When the volcano finally had its massive eruption, spewing ash 15 miles high into the sky above, the northern side of the volcano crumbled off and killed 57 people in the town below.