The effects of a volcanic eruption can be intense and far-reaching. Hazards associated with volcanoes can alter the surrounding landscape, destroy property, and cause injury and death. The key to keeping safe from a volcano is understanding the behavior of these hazards.
Hazards Associated With Volcanic Eruptions
In his book Earth: Portrait of a Planet, Stephen Marshak identifies eight specific types of volcanic hazards. These hazards are
- lava flows
- ash falls
- pyroclastic flows
- lahars
- landslides
- earthquakes
- tsunamis and
- toxic gases.
Lava flows can quickly cover a broad area, burying roads, homes, and farms. Many structures burst into flames as the lava approaches due to the intense heat.
Ash falls occur after an eruption and can blanket surrounding areas with ash up to several meters thick. Ash is hazardous to breathe, and ash falls spread toxic chemicals released by the volcano, kill crops and livestock, and can damage machinery such as cars. Eruptions also disrupt air travel since ash has destructive effects on airplane parts and engines.
A pyroclastic flow is a superheated cloud of ash, boulders, debris, and volcanic gases. Moving at speeds up to 300 kilometers per hour, the flows are capable of knocking over and incinerating buildings and trees, and can mean instant death to anyone caught in their paths. Pyroclastic flows can travel hundreds of kilometers from the site of the eruption.
Lahars form when volcanic debris mixes with water, forming a substance with the consistency of wet cement. The water is supplied by heavy rains or snowmelt. Lahars move quickly, often at speeds of 50 kilometers per hour or greater, following the landscape’s existing drainage patterns. They can travel far from the eruption site, burying towns and destroying buildings, forests, and bridges along the way.
Landslides are moving masses of rock, soil, debris, ash, and solidified lava. Eruptions can trigger slides along a volcano’s flank as the blast weakens the slopes. Landslides can move at speeds up to 250 kilometers per hour, forever altering the surrounding landscape.
Earthquakes accompany almost all major volcanic eruptions and can often signal that an eruption is imminent. These earthquakes are caused by the underground movement of magma, which travels between rocks, breaking and altering them. The magma can also turn groundwater to steam, leading to explosions that also cause the earth to move. Earthquakes in and around volcanoes can also trigger volcanic landslides.
Tsunamis can occur after an eruption at sea. Waves are triggered by volcanic blasts, precursory earthquakes, massive landslides, and volcanic collapse. The resulting waves can be tens of meters high and devastate coastal communities.
Toxic gases do not require an eruption in order to be in the vicinity of a volcano. Volcanoes can release many different types of gases at any time. These gases include water vapor, carbon dioxide, sulfur dioxide, and hydrogen sulfide. By displacing available oxygen in the area, these gases can kill people and livestock. Large concentrations of volcanic gases can also kill forests and crops. In fact, large-scale tree kills are a good indication of increased volcanic activity.
Preparing for Volcanic Hazards
There is not much that can be done to prevent volcanic processes from occurring. Therefore, it is important for those living in close proximity to volcanoes to take the proper steps to mitigate volcanic hazards. Residents should prepare disaster plans, know the location of high ground in their area, and heed warnings from local governments and emergency management teams. It is also important for residents to understand the types of volcanic hazards and know the likelihood of their occurrence in their particular area.
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