Physical Factors Of Volcanoes

A volcano is a surface landform resulting from the extrusion of magma from underground as lava, ash, rocks, and gasses are erupted in various proportions. Each year, around 60 major volcanoes erupt globally. How hazardous each one is dependent on a variety of human and physical factors that determine the level of impact on human activity that each event exerts. I will be looking at how the physical properties of a volcano, interact with human variables to make certain volcanoes more hazardous than others. This essay will incorporate exemplification from countries at different stages of development to discuss human factors and how this links with their physical geography. The scale will be primarily global; both development spread and tectonic …show more content…
Volcanoes are generally found in three locations: constructive and destructive plate boundaries, as well as hotspots. The most explosive and potentially the most hazardous volcanoes are found on destructive, convergent plate boundaries. Here, one plate subducts beneath the other generating intense heat and pressure, melting the rock and sediment to form an acidic magma chamber. This viscous magma is resistant to flow and therefore results in violent, dangerous eruptions involving pyroclastic material and ash; potentially hazardous both locally and globally. Another factor associated with destructive boundaries is the presence of the phreatic zone: explosive volcanic activity involving steam derived from water that has been trapped as a plate subducts. At constructive/divergent boundaries, the emerging lava is generally basic and therefore has a low viscosity, allowing it to flow easily causing much less violent eruptions. Events occur frequently but not explosively at constructive plate margins. A good example is the Mid Atlantic Ridge where the ocean floor is lined with constant, low risk volcanic activity. The hazard capacity of constructive margins generally increases when activity emerges above sea level, as seen with Iceland. However, the risk still remains low, with the exception of distinct events in which other factors have contributed. The recent Eyjafjalajakul eruption (2010) caused major global disruption, especially to Northern Europe. In this instance, the ice cap situated on top of the main vent was primary in causing the major ash cloud: this is another physical factor. Eruptions can also occur on hotspots, but the magma associated with these volcanoes is generally of low viscosity and basic in nature, producing similar events to those found at divergent boundaries. Volcanoes generally don`t form at collision boundaries. Whilst 75% of all volcanic material