Volcanic hazards

A Volcanic hazard is the probability that a volcanic eruption or related geophysical event will occur in a given geographic area and within a specified window of time. The risk that can be associated with a volcanic hazard depends on the proximity and vulnerability of an asset or a population of people near to where a volcanic event might occur.

There are different forms of effusive lava that can provide different hazards. Pahoehoe lava is smooth and ropy while Aa lava is blocky and hard. Lava flows normally follow the topography, sinking into depressions and valleys and flowing down the volcano. Lava flows will bury roads farmlands and other forms of personal property. This lava could destroy homes, cars, and lives standing in the way. Lava flows are dangerous, however, they are slow moving and this gives people time to respond and evacuate out of immediate areas. People can mitigate this hazard by not moving to valley or depressed areas around a volcano.

Tephra is a generalized word for the various bits of debris that are launched out of a volcano during an eruption, regardless of their size.Pyroclastic materials are generally categorized according to size: dust measures at <1/8 mm, ash is 1/8–2 mm, cinders are 2–64 mm, and bombs and blocks are both >64 mm. There are different hazards associated with the different kinds of pyroclastic materials. Dust and ash could coat cars and homes, rendering the car unable to drive with dust accumulation in the engine. They could also layer on homes and add weight to roofs causing the house to collapse. Also, ash and dust inhaled could cause long-term respiratory issues in people inhaling the particles. Cinders are flaming pieces of ejected volcanic material which could set fire to homes and wooded areas. Bombs and blocks run the risk of hitting various objects and people within range of the volcano. Projectiles can be thrown thousands of feet in the air and can be found several miles away from the initial eruption point.

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