Volcanic Eruptions: Types and Safety Measures

Study Notes

Volcanic Eruptions

Volcanic eruptions are the explosive and non-explosive expulsion of gas, magma, and volcanic ash from a volcano. They can be the result of heat moving beneath Earth's surface and the accumulation of gas-rich magma near the surface. Eruptions can range from gentle outflows of lava, as seen in Hawaiian volcanoes, to massive and destructive events, like the eruption of Vesuvius that destroyed Pompeii in 79 CE.

How Volcanoes Erupt

Volcanic eruptions often begin with the accumulation of gas-rich magma in reservoirs near the surface. However, they may also be preceded by emissions of steam and gas from small vents in the ground. Small earthquakes, which can be caused by a rising plug of dense, viscous magma oscillating against a sheath of more permeable magma, may signal an eruption.

In some cases, magma rises to the surface as a thin and fluid lava. This can either flow out continuously or shoot straight up in glowing fountains or curtains. The eruptions of Hawaii's volcanoes fall into this category. In more violent eruptions, entrapped gases tear the magma into shreds, and viscous clots of lava are hurled into the air. In even more explosive eruptions, the magma conduit is hollowed out by an explosive blast, and solid fragments are ejected in a great cloud of ash-laden gas that rises tens of thousands of meters into the air.

Volcanic Hazards

Volcanic eruptions can pose several hazards. These include volcanic ash, gases, lahars (mud flows), landslides, lava flows, and pyroclastic flows (fast-moving currents of hot gas). These hazards can be deadly and often cause population displacement and food shortages.

Preparing for Volcanic Eruptions

To prepare for a volcanic eruption, it is essential to assess and plan. Learn your volcano risks and warning signs, and be aware of secondary hazards such as landslides and lahars. Participate in early warning systems and develop plans for both evacuating and sheltering in place.

Additionally, reduce risks by protecting your home from volcanic ash and covering water sources if time allows. Avoid driving during and after ash fall when visibility can be very low and roads are slippery. Protect your lungs and eyes by wearing protective gear such as goggles and masks.

Finally, prepare to respond. Follow official instructions from local authorities on whether to evacuate or take shelter. If you get warning prior to ash fall, return home from school or work and shelter in place. If the ash fall is heavy, do not remain in a building that has a low-pitched or flat roof.

Do's and Don'ts

Assess and plan
Learn your volcano risks and warning signs
Become familiar with volcano hazard maps and danger zones
Participate in early warning systems
Be aware of secondary risks such as landslides and flash floods
Avoid driving during and after ash fall
Support vulnerable people to evacuate or shelter in place safely
Store clean water and food
Protect your eyes and lungs with goggles and masks
Prepare and practice evacuating or sheltering in place

Classification of Volcanic Eruptions

Volcanic eruptions can be classified by the manner in which they erupt. These six types of volcanic eruptions, starting with the least explosive, make up one classification system: Icelandic, Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian. Each name corresponds to a region or to a specific volcano or historical eruption that exemplifies the type.

Description

Learn about the different types of volcanic eruptions and the safety measures to prepare for and respond to volcanic hazards. Explore the classification of volcanic eruptions, from gentle outflows of lava to massive and destructive events, and understand how to protect yourself and your community in case of an eruption.